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Da Silva, Ashley.
Investigation of cretaceous molluscan shell material for isotopic integrity :
b examples and implications from the baculites compressus/cuneatus biozones (Campanian) of the western interior seaway
h [electronic resource] /
by Ashley da Silva.
[Tampa, Fla] :
University of South Florida,
ABSTRACT: Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles.As a study sample, mollusks from the Baculites compressus and Baculites cuneatus biozones of the Western Interior Seaway of North America were collected from three locations: Kremmling, Colorado; Trask Ranch, South Dakota; Game Ranch, South Dakota. These fossils date to the Campanian (Late Cretaceous). Taxa include ammonites, bivalves, gastropods, and nautiloids. The first part of this investigation, described in Chapter 2, investigates the degree of ^alteration in these specimens. Elevated concentrations of minor elements such as magnesium and strontium reveal alteration from the original aragonite and/or calcite skeletons. Concentrations of these elements obtained by ICP-OES analysis are compared within several suites of specimens: mode of preservation, shell testing location, shell color, cementation, appearance under light microscope, and appearance under scanning electron microscope. Each of these suites tests a hypothesis about optimal shell preservation. Shell was found to be preserved best in shale rather than concretions, ammonite phragmacone rather than septa, opalescent specimens rather that non-opalescent ones, and uncemented shells rather than cemented shells, especially those with second-order versus first-order cement. Salinity and temperature values were derived for the organisms in the Western Interior Seaway: while bivalves produced unusually low temperatures, the others were reasonable for an inland sea. The ^second part of this study, described in Chapter 3, examines the isotopic record within exemplary mollusk shells, taken perpendicular to growth lines. The data for this investigation in sclerochronology documents the dominant isotopically enigmatic bottom-water habitat of the Inoceramus, the geochemical signature of the overlying water mass inhabited by Baculites, and short-term migrations between the two water masses in the nautiloid Eutrephoceras.
Thesis (M.A.)--University of South Florida, 2006.
Includes bibliographical references.
Text (Electronic thesis) in PDF format.
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Adviser: Peter J. Harries, Ph.D.
t USF Electronic Theses and Dissertations.
Investigation of Cretaceous Molluscan Shell Material for Isotopic Integrity: Examples and Implications from the Baculites compressus/cuneatus Biozones (Campanian) of the We stern Interior Seaway by Ashley da Silva A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Geology College of Arts and Sciences University of South Florida Major Professor: Peter J. Harries, Ph.D. Gregory S. Herbert, Ph.D. Eric A. Oches, Ph.D. Date of Approval: April 11, 2006 Keywords: Cretaceous, Campanian, epicontinental sea, paleoclimatology, paleooceanography, fossil preservation, mollusks, oxygen, carbon, minor elements Copyright 2006, Ashley da Silva
i DEDICATION I dedicate this MasterÂ’s thesis to teachers of science. This is not because it is a study in science education, because it is not. This thesis is, however, part of the education of a science teacher. Experience with the scientific method and both the excitement and complications of scientific research should serve me well in communicating the nature of science to students. I hope that reading this document will help others who I do not formally teach to learn something about fossils, their preservation, and the paleooceanographic information they can contain. I also dedicate this MasterÂ’s thesis to teachers of science that I have been fortunate enough to learn from. Some of them have been in middle schools, high schools, and universities; others teach informally. These teachers have: (1) Rewarded curiosity; the fundamental first step in scientific research (2) Brought science home from research journals and newsmagazines into the classroom (3) Defined science as a process undertaken by people, rather than a body of knowledge Without support from exemplary teachers of science, I, and, I suspect, many students of science, would not be realizing their scientific curiosity with research.
ii ACKNOWLEDGMENTS I would like to acknowledge the contributions of the University of South Florida Department of Geology, especially Dr. Peter Harries, for providing necessary facilities, fossil collection opportunities, and financial support. I would like to thank my committee members, Dr. Gregory S. Herbert and Dr. Eric A. Oches, for their valuable perspectives shared during this project. I would also like to acknowledge Dr. Terrence M. Quinn for use of his laboratory at the USF Marine Science campus in St. Petersburg, and to Ethan Goddard for running my samples on the ICP-OES and mass spectrometer there. I would like to acknowledge the research of my colleagues, Dr. Neil Landman and Kathleen Sarg at the American Museum of Natural History, and Dr. Kirk Cochran at the State University of New York Â– Stonybrook. This investigation is a part of a National Science Foundation-funded grant, and I give thanks to the NSF for the financial support. I would like to thank Neal Larson of the Black Hills Institute of Geological Research for the Eutrephoceras specimens used for sclerochronology. Likewise, I would like to thank William Cobban for samples of Baculites and Didymoceras. I would like to acknowledge the Geological Society of America for allowing me to present this research at their 2005 annual meeting, and both the Southeastern Section of GSA and the USF Graduate Student Orga nization for providing travel reimbursement. Lastly, I would like to thank my family for being supportive of my undertaking of a MasterÂ’s degree and their patience with the time demands of my work.
iii TABLE OF CONTENTS LIST OF TABLES iv LIST OF FIGURES v ABSTRACT vii 1. INTRODUCTION 1.1 An Introduction to the Western Interior Seaway 1 1.2 Biozones Selected for Study 2 1.3 Locations Selected for Study 5 1.4 Fossils Recovered 6 2. SHELL ALTERATION INVESTIGATION 2.1 Previous Investigations of Molluscan Fossil Shell Alteration 13 2.2 Methods 19 2.3 Results 28 2.4 Discussion 67 3. SCLEROCHRONOLOGY INVESTIGATION 3.1 Previous Investigations of Molluscan Sclerochronology 100 3.2 Methods 103 3.3 Results 108 3.4 Discussion 128 4. CONCLUSIONS 136 REFERENCES 140 APPENDICES Appendix A: Shell Alteration Mass Spectrometer Data 146 Appendix B: Shell Alteration ICP Data 156 Appendix C: Sclerochronology ICP Data 192 Appendix D: Sclerochronology Mass Spectrometer Data 208
iv LIST OF TABLES TABLE 1 Â—Upper Campanian Biozones for the Western Interior Seaway 4 TABLE 2 Â—Fossil Genera Investigated in this Study 11 TABLE 3 Â—Morphology of Ammonites Investigated in this Study 12 TABLE 4 Â—Specimen Suites Used in Shell Alteration Investigations 22 TABLE 5 Â—Detection Limits for ICP-OES System 25 TABLE 6 Â—Summary Statistics for Mode of Preservation Suite 32 TABLE 7 Â—Summary Statistics for Â“Shell Sampling PositionÂ” Suite 40 TABLE 8 Â—Descriptive Names for Munsell Designations of Shell Color Classes 46 TABLE 9 Â—Summary Statistics for Â‘Shell ColorÂ’ Suite: Shell Opalescence 47 TABLE 10 Â—Summary Statistics for Â‘Shell ColorÂ’ Suite: Shell Color 48 TABLE 11 Â—Colors for Unaltered Shell, by Genus 51 TABLE 12 Â—Summary of Statistical Tests on Cemented and Uncemented Shell 60 TABLE 13 Â—Statistical Tests for Kremmling Cements, Concretions, and Shell 64 TABLE 14 Â—Statistical Tests for Game Ranch Concretions and Shell 65 TABLE 15 Â—Statistical Tests for Trask Ranch Cements, Concretions, and Shell 66 TABLE 16 Â—Statistics Comparing 18O of Pre-filter and Post-filter Datasets 95 TABLE 17 Â—Statistics Comparing 13C of Pre-filter and Post-filter Datasets 97 TABLE 18 Â—Paleoenvironmental Parameters Derived from Filtered Data 98
v LIST OF FIGURES FIGURE 1 Â—Extent of the Western Interior Seaway During the Baculites compressus/Baculites cuneatus Biozones 9 FIGURE 2 Â—Mode of Preservation Stable Isotope Cross-Plot 31 FIGURE 3 Â—Sr/Ca and Mg/Ca Ratios for Â“Mode of PreservationÂ” Suite 33 FIGURE 4 Â—Radar Charts for Minor Element Concentrations in the Â“Mode of Preservation SuiteÂ” 34 FIGURE 5 Â—Shell Sampling Position Stable Isotope Cross-Plot 39 FIGURE 6 Â—Shell Sampling Position Sr/Ca-Mg/Ca Cross-Plot 41 FIGURE 7 Â—Radar Charts for Minor Elements in Â“Shell Sampling PositionÂ” Specimens 42 FIGURE 8 Â—Shell Color Stable Isotope Cross-Plot 49 FIGURE 9 Â—Shell Color Sr/Ca-Mg/Ca Cross-Plot 50 FIGURE 10 Â— Radar Charts for Minor Elements in Cemented and Uncemented Shell 57 FIGURE 11 Â—Minor Element Content of Â“Cementation Suite SamplesÂ” 58/59 FIGURE 12 Â—Comparison of Cements, Concretions, and Shell Material for Kremmling 61 FIGURE 13 Â—Comparison of External Recrystallizations or Cements, Concretions, and Shell Material for Game Ranch 62 FIGURE 14 Â—Comparison of Cements, Concretions, and Shell Material for Trask Ranch 63 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter 8590
vi FIGURE 16 Â—Stable Isotope Cross Plot for All Shell Samples 92/93 FIGURE 17 Â—Isotope Cross-Plot For All Shell Samples, Filtered by Mg/Ca and Sr/Ca 106107 FIGURE 18 Â—Oxygen Isotope Range Chart 94 FIGURE 19 Â— Carbon Isotope Range Chart 96 FIGURE 20 Â—Stable Isotope Ranges for Genera in this Study and Prior Research 99 FIGURE 21 Â—Specimens Used in Sclerochronology 97/98 FIGURE 22 Â—Minor Element Ratios for Sclerochronology: Bivalves 111 FIGURE 23 Â—Sclerochronology of Inoceramus Specimen I2 112 FIGURE 24 Â— 18O Versus 13C for Inoceramus Specimen I2 113 FIGURE 25 Â—Calculated Paleotemperature and Paleosalinity through Â“OntogenyÂ” in Inoceramus Specimen I2 114 FIGURE 26 Â— Minor Element Ratios for Sclerochronology: Baculites 117 FIGURE 27 Â—Sclerochronology of Baculites Specimen B7 118 FIGURE 28 Â—Stable Isotope Sclerochronology of Baculites Specimen B7 119 FIGURE 29 Â— 18O Versus 13C in Baculites Specimen B7 120 FIGURE 30 Â—Calculated Paleotemperature and Paleosalinity in Baculites Specimen B7 121 FIGURE 31 Â—Sclerochronology of Eutrephoceras Specimen E2 124 FIGURE 32 Â—Stable Isotope Sclerochronology of Eutrephoceras Specimen E2 125 FIGURE 33 Â— 18O Versus 13C in Eutrephoceras Specimen E2 126 FIGURE 34Â— Calculated Paleotemperature and Paleosalinity in Eutrephoceras Specimen E2 127
vii INVESTIGATION OF CRETACEOUS MOLLUSCAN SHELL MATERIAL FOR ISOTOPIC INTEGRITY: EXAMPLES AND IMPLICATIONS FROM THE BACULITES COMPRESSUS/CUNEATUS BIOZONES (CAMPANIAN) OF THE WESTERN INTERIOR SEAWAY Ashley da Silva ABSTRACT Whether a global greenhouse interval is a distinct or distant future, it is important to understand the dynamics of a greenhouse system. During such intervals the oceans, in the absence of sizeable polar ice caps, flood the continental shelf. The stratification and circulation of these epicontinental seas are open to debate, because there are no Recent analogs. The carbon and oxygen stable isotope record of fossil molluscan shell from epicontinental seas has the potential to reveal their stratification and seasonal cycles. As a study sample, mollusks from the Baculites compressus and Baculites cuneatus biozones of the Western Interior Seaway of North America were collected from three locations: Kremmling, Colorado; Tras k Ranch, South Dakota; Game Ranch, South Dakota. These fossils date to the Campanian (Late Cretaceous). Taxa include ammonites, bivalves, gastropods, and nautiloids. The first part of this investigation, described in Chapter 2, investigates the degree of alteration in these specimens. Elevated concentrations of minor elements such as magnesium and strontium reveal alteration from the original aragonite and/or calcite skeletons. Concentrations of these elements obtained by ICP-OES analysis are compared within several suites of specimens: mode of preservation, shell testing location, shell
viii color, cementation, appearance under light microscope, and appearance under scanning electron microscope. Each of these suites tests a hypothesis about optimal shell preservation. Shell was found to be preserved best in shale rather than concretions, ammonite phragmacone rather than septa, opalescent specimens rather that nonopalescent ones, and uncemented shells rather than cemented shells, especially those with second-order versus first-order cement. Salinity and temperature values were derived for the organisms in the Western Interior Seaway: while bivalves produced unusually low temperatures, the others were reasonable for an inland sea. The second part of this study, described in Chapter 3, examines the isotopic record within exemplary mollusk shells, taken perpendicular to growth lines. The data for this investigation in sclerochronology documents the dominant isotopically enigmatic bottom-water habitat of the Inoceramus the geochemical signature of the overlying water mass inhabited by Baculites and short-term migrations between the two water masses in the nautiloid Eutrephoceras
1 CHAPTER 1. INTRODUCTION 1.1 An Introduction to the Western Interior Seaway The Western Interior Seaway, an epicontinental sea during the Cretaceous Period, has no modern analog. The seaway connected with open oceanic conditions in the north and south, unlike the restricted circulation of todayÂ’s Hudson Bay, Persian Gulf, or North Sea. Reconstructing how these bodies of water affected global temperatures, water circulation, and biological migration and e volution patterns requires knowledge of the nature of water masses within these seaways. Several models for the structure of the Western Interior Seaway have been proposed. Of particular concern is the fate of the fresh water entering the basin from the east, as well as from the Sevier Orogenic Belt to the west. Wright (1987) argues, based on stable-isotope data from mollusk shells and whole-rock samples, that the intermediate waters in which most ammonites lived were cooler and less saline than the deep waters the bivalves inhabited. The models call for above-normal salinity in the bottom water due to coastal evaporation and subsequent sinking or below-normal salinity for the intermediate water due to high freshwater runoff rates, respectively. Tsujita and Westermann (1998) added a third layer Â– a Â“brachyhaline water capÂ” extending from the shoreline and tapering off towards the center of the seaway -to explain their very light 18O values for Placenticeras ammonites. In contrast, Slingerland (1996) argues for greater estuarine circulation and mixing in the Western Interior Seaway, such that the salinity stratification only exists near the coasts where freshwater was input. It is certainly possible that at different times, the general
2 paleoceanographic circulation pattern of the Western Interior Seaway differed. For this study, two biozones in the Upper Campanian were selected. The sites in this investigation represent nearly synchronous deposits, so that any variation in circulation patterns with time is minimized, and included both nearshore and deeper-water environments. Biozones Selected for Study 1.2.1 Selection of Biozones : The two biozones of the Upper Campanian that were selected were the Baculites compressus and B. cuneatus biozones. These zones are named for two common orthoconic heteromorph ammonites. The two biozones are often grouped together because of the uncertainty in the numeric date for the boundary between the two zones (Scott and Cobban, 1986) and the apparent stratigraphic overlap between the two ammonite species. Selection of the biozones was part of a larger study, funded by the National Science Foundation and in collaboration with the American Museum of Natural History, New York, to analyze molluscan oxygen, carbon, and strontium isotopes across the former Western Interior Seaway. The stratigraphic formation investigated is called the Pierre Shale in all sampling locations, although the lithologic characteristics of the unit differ between the Colorado and South Dakota locations. A summary of the basic lithologic characteristics of the Upper Campanian outcrops, including the Baculites compressus and B. cuneatus biozones, is presented in Table 1.
3 1.2.2 Fauna of the Biozones : The ammonites collected from these biozones consist of species within Baculites, Solenoceras, Axonoceras, Anaklinoceras, Cirroceras, Didymoceras, Pachydiscus, Placenticeras, Hoploscaphites, and Jeletzkytes Except for the occassional Pachydiscus specimen, Placenticeras is the only planispiral ammonite represented; the remainder are all heteromorphic forms. The nautiloid Eutrephoceras occurs in the biozones. Bivalves include abundant Inoceramus less frequent Anomia and many other genera present in low abundances. Gastropods are uncommon and small in size. 1.2.3 Prior Research in the Baculites compressus and Baculites cuneatus Biozones: Because of the abundance of fossils in the Baculites compressus / cuneatus biozones, they have been used in previous paleooceanographic studies. One of the first studies on stable isotopes using fossil mollusks, by Tourtelot and Rye (1969), used the 18O ratio of Baculites specimens and belemnites to conclude that the Western Interior Seaway ranged from 21-33 oC, significantly warmer then the Atlantic coast, which was 17-23 oC at the time. The authors also found lighter oxygen isotopes and heaver carbon isotopes for their bivalve samples (inoceramids and oysters) than for their baculitid samples. This research is supported by Forester et al. (1977), who found an average 18O paleotemperature of 25 oC for the Baculites compressus biozone and 20 oC for the Baculites cuneatus biozone in southern Saskatchewan. He et al (2005) disputed the difference in temperature between the two biozones using a more robust collection of baculitid specimens, from both the United States and Canada. They did, however, note a general trend toward heavier isotopic values coinciding with marine regression, which peaked during the biozones of interest. Their isotopic values for Baculites and
4 Inoceramus specimens are similar to those of Tourtelot and Rye (1969), but they add data points for the heteromorph ammonites Didymoceras and Scaphites which fall between the Inoceramus and Baculites fields. Schmidt (1997) observed an overlap between epifaunal (primarily, bivalve) and nektonic (pri marily, ammonite) stable isotope fields for the Western Interior Seaway. Tsujita and Westermann (1998) attempted to resolve paleotemperatures recorded by ammonites in the uppermost Campanian to the species level, but their intrageneric conclusions are hampered by a small dataset. They noted unrealisticly high paleotemperatures for Inoceramus and also very light 18O (mean = -5.2Â‰ versus the Pee Dee Belemnite standard) in Placenticeras which they attribute to low salinity in the uppermost part of the water column but which probably reflect diagenetically altered material (Landman, pers. comm., 2005) Stable isotope sclerochronology has been performed on ammonites, bivalves, and the nautiloid Eutrephoceras Because of their common occurrence, long generic stratigraphic ranges, and tendency to be preserved more completely than Hoploscaphites or Placenticeras members of the genera Baculites and Inoceramus have been studied extensively. Tourtelot and Rye (1969) found a sinusoidal 18O curve in a Baculites section, with one minimum and two maxima. The 18O range of this baculitid was from -0.8Â‰ to -1.2Â‰, equivalent to a 1.5 oC temperature difference. The 13C curve for this specimen shows a direct relationship with age of the organism, and has superimposed maxima and minima paralleling the oxygen curve. Fatherree et al (1998) show a slightly larger range (0.2Â‰ to -1.2Â‰) in a larger Baculites section. These authors note an inverse relationship between 18O and 13C, consistent with temperature being the most significant variable reflected in the isotopic signatures. Along the first six and the last
5 eight centimeters of the shell, however, the 13C curve parallels the 18O curve. Likewise, Landman et al. (1983) document a positive correlation between 13C and 18O between the first nine septa in a Western Interior Seaway Eutrephoceras after which the correlation becomes negative. Fatherree (1995) documents an inverse relationship between 13C and 18O in the bivalve Artica ovata and a direct relationship between them in another bivalve, Inoceramus sagensis Tourtelot and Rye show an approximately parallel set of 13C and 18O maxima for their Inoceramus example. These investigations both calculate Inoceramus paleotemperatures above 30oC, a temperature that is at the upper limit for shell precipitation in Recent bivalves. Because inoceramids have no close living relatives, explanations from high-salinity environmental preferences to symbiotic bacteria have been generated to explain the unrealistic 18O paleotemperatures. 1.2 Locations Selected for Study 1.3.1 Kremmling, Colorado, Sampling Site: The Kremmling, Colorado, sampling site was located on the United States Bureau of Land Management Ammonite Preserve, north of the town of Kremmling, Colorado. Geographic coordinates were 40o14Â’N, 106o23 to 106o24Â’W. The outcrops, exposed on hilltops, were comprised of beige siltstone (Munsell color designations 2.5YR7/5 to 2.5YR7/6) with three stratigraphic horizons of concretions. The concretions, up to one meter in diameter, weathered to the same color as the siltstone, but were a light grey (5YR3/2) upon a fresh surface.
6 1.3.2 Game Ranch, South Dakota, Sampling Site : The Game Ranch, South Dakota site was located on a tall cutbank, within a private ranch on the southeastern rim of the Black Hills near the town of Farmingdale. Geographic coordinates were 43o55Â’N, 102o50Â’W. The lithology was a black, fissile shale (Munsell designation 5YR3/2 when dry) containing concretions and fossils preserve d directly in the shale. Concretions were small, usually containing a single fossil, and had a reddish 10YR2/4 interior and an orange 10YR6/10 weathering rind. Concretionary horizons were obscured by shale erosion. 1.3.3 Trask Ranch, South Dakota, Sampling Site: The Trask Ranch, South Dakota, site was located on a private ranch, also on the southeastern side of the Black Hills. Geographic coordinates for this site were 44o14Â’N, 102o28Â’W. Large (25 cm to 1 m) concretions were dispersed in a riverbed; from these, numerous fossils were recovered. Some concretions contained mostly intact fossils, while others contained a Â“shell hashÂ” of small broken fragments. Concretions at this site were 5YR3/2 to 5YR5/2 in color. Some showed veins of calcite crystals typical of septarian concretion, but ferrous weathering rinds were not well-developed as in the Game Ranch specimens. 1.4. Fossils Recovered 1.4.1 Fossils from Kremmling, Colorado : At the Kremmling, Colorado, site, large, numerous Placenticeras -including mature macroconchs, mature microconchs, and juveniles -were found (though most were internal and external molds with limited shell preservation). Classification for Placenticeras and other genera examined in this study is summarized in Table 2. One of the Placenticeras specimens had limpets of the
7 genus Anisomyon adhering to its shell, but these had little to no shell material preserved. Specimens of Hoploscaphites and Baculites were also relatively common. Baculites specimens appeared to be Baculites compressus but many specimens were crushed, making evaluation of the amount of inflation, a key identification parameter, difficult. One Axonoceras compressum and two Anaklinoceras gordiale specimens were found, suggesting that the location is part of the Baculites compressus biozone. The morphology of these ammonites and others used in this investigation are described in Table 3. Unfortunately, the quantity of shell preserved on these tiny heteromorph ammonites did not allow for chemical analysis. Partial specimens of the nautiloid Eutrephoceras also had insufficicient shell material. Bivalves recovered included numerous Inoceramus some preserved with calcitic and aragonitic layers together, but most with layers separated. Anomia was also represented, as were small (< 1 cm) bivalves and gastropods not identified in this study. 1.4.2 Fossils from Game Ranch, South Dakota: At the Game Ranch, South Dakota, site, Hoploscaphites was nearly absent. Placenticeras Baculites and Inoceramus were all present in both shale and concretions. Fossils did not appear to be compressed or otherwise deformed. Five Nymphalucina bivalves were discovered in the shale. In addition, two specimens each of Anomia and a scaphopod were collected. Only the bivalves were complete.
8 1.4.3 Fossils from Trask Ranch, South Dakota: At the Trask Ranch, South Dakota, Placenticeras was absent and Hoploscaphites fairly common. Baculites was the most common ammonite at the site. The most common bivalve was Inoceramus, and some concretions contained only specimens of this genus. Rarer genera, for which two to five specimens were collected, include the bivalve Nymphalucina and the gastropods Drepanocheilus and Anisomyon A single scaphopod was also found. Some fossils were partial or shattered, especially those in the Â“fossil hashÂ” concretions, but many others appeared to be complete and undeformed. Two specimens of the nautiloid Eutrephoceras were collected from the site by Neal Larson, Black Hills Institute of Geological Research, and sent for the sc lerochronology portion of this project. 1.4.4 Sampling Bias: The specimens collected at the three sampling locations are in no means an accurate, proportional sample of the Western Interior Seaway fauna from 73 Ma. Fossilization biases likely exist. Thin-shelled Anomia for instance, may have been more common in the seaway than it is in the Kremmling deposits. Small specimens, such as the gastropods and bivalves, could easily have been overlooked during collection. Fossils with a large amount of preserved shell were preferentially collected. Lastly, generic variety was one of the goals in collection, so some specimens of common genera such as Baculites and Inoceramus were passed by in favor of less-common genera such as Hoploscaphites
9 FIGURE 1 Â—Extent of the Western Interior Seaway in the United States During the Baculites compressus / Baculites cuneatus Biozones. Key: Lowermost Maastrichtian Uppermost Upper Campanian Middle Upper Campanian ( B. compressus/B. cuneatus biozones) Lower Upper Campanian Middle Cenomanian The sample sites for this study are located in the western and central parts of the former Western Interior Seaway. Contemporaneous outcrops also occur in southern Saskatechewan, near the western shoreline of the seaway, and in east-central South Dakota, near the eastern shoreline. Shoreline taken from Larson et al., 1997; data for locations from the American Museum of Natural History (2005).
10 TABLE 1 Â—Upper Campanian Biozones for the Western Interior Seaway Ammonite biozone Radiometric Ages from Bentonites (Larson et al., 1997) Dominant Lithology, Kremmling, Colorado (Scott and Cobban, 1986) Dominant Lithology, Trask Ranch and Game Ranch, South Dakota, (Larson et al., 1997) Baculites jenseni Upper boundary = 71.3 0.5 Ma Lower portion siltstone; upper portion sandstone with bentonitic shale beds; both bear ironstone concretions Unconformity Baculites reesidei Shale with sparse ironstone concretions Dark grey, fissile shale with septarian concretions Baculites cuneatus Shale with septarian concretions Dark grey, fissile shale with septarian concretions Baculites compressus 73.35 0.39 MaSiltstone and large dated bentonite bed in lower portion; shale in upper portion; both with septarian concretions Dark grey, fissile shale with septarian concretions Didymoceras cheyennense Siltstone in lower portion, sandstone in upper portion; both with septarian concretions Bentonitic shales Exiteloceras jenneyi 74.6 0.72 Ma Alternating sandstones and shales with septarian concretions Dated bentonite, bentonitic shales Didymoceras stevensoni Alternating sandstones and shales with septarian concretions Dark grey, fissile shale with septarian concretions Didymoceras nebrascense Alternating sandstones and bentonitic shales with septarian and ironstone concretions Dark grey, fissile shale with septarian concretions The lithology of the Baculites compressus/Baculites cuneatus biozones is dominated by dark grey, fissile shale in South Dakota. The Kremmling, Colorado, site also includes siltstones. Both locations contain septarian concretions. The Baculites compressus biozone has been dated to approximately 73.4 Ma.
11 TABLE 2 Â–Fossil Genera Investigated in this Study Phylum Mollusca Class Bivalvia (Linnaeus, 1758) Subclass Heterodonta (Neumayr, 1884) Order Myoida (Goldfuss, 1820) Family Teredinidae (Rafinesque, 1815) Teredo (Linnaeus, 1758) Order Veneroida (H and A Adams, 1856) Family Lucinidae (Fleming, 1828) Nymphalucina (Speden, 1970) Subclass Pteriomorphia (Beurlen, 1944) Order Ostreoida (Frussac, 1822) Family Anomiidae (Rafenisque, 1815) Anomia ( Linneaus 1758 ) Order Pterioida (Newell, 1965) Family Inoceramidae2 (Giebel, 1852) Inoceramus (J. Sowerby, 1814) Class Cephalopoda3 (Cuvier, 1797) Subclass Ammonoidea (Author unknown) Order Ammonitida (Hyatt, 1889) Family Baculitidae (Gill, 1871) Baculites (Lamarck, 1799) Family Nostoceratidae (Hyatt, 1894) Cirroceras (Conrad, 1868) Didymoceras (Hyatt, 1894) Family Placenticeratidae (Hyatt, 1900) Placenticeras (Meek, 1870) Family Scaphitidae (Meek, 1876) Hoploscaphites (Nowak, 1911) Jeletzkytes (Riccardi, 1983) Subclass Nautiloidea (Agassiz, 1847) Order Nautilida (Agassiz, 1847) Family Nautilidae (Blainville, 1825) Eutrephoceras (Hyatt, 1894) Class Gastropoda4 (Cuvier, 1797) Subclass Prosobranchia (Edwards,1848) Order Basommatophora (Schmidt, 1855) Family Siphonariidae (Gray, 1840) Anisomyon (Meek and Hayden, 1860) Order Mesogastropoda (Thiele, 1925) Family Aporrhaidae (Morch, 1852) Drepanocheilus (Meek, 1876) 1 Classification follows Speden (1970) 2 -Classification follows Walaszczyk and Cobban, 20003 Classification follows Besnosov and Michailova, 1991; Larson et al., 1997 4 Classification follows Abdel-Gawad, 1986
12 TABLE 3 Â—Morphology of Ammonites Investigated in this Study Protoconch & Neanoconch Juvenile Adult Baculites Planispiral Orthoconic Orthoconic Hoploscaphites Planispiral Planispiral (moderately inflated) J-shaped or U-shaped chamber Anaklinoceras Planispiral Turritellid spire Inverted U-shaped chamber ( A. gordiale ) or planispiral ( A. reflexum ) Axonoceras Planispiral Planispiral (inflated), separated whorls Planispiral (inflated), separated whorls Placenticeras Planispiral Planispiral (compressed) Planispiral (compressed) Many of the types of ammonites found in the sampling sites for the Baculites compressus and Baculites cuneatus biozones exhibit vast changes in growth program across different growth stages. In others, the transition between growth stages is marked by changes in shell ornamentation alone.
13 CHAPTER 2. SHELL ALTERATION INVESTIGATION 2.1 Previous Investigations of Molluscan Fossil Shell Alteration 2.1.1. Rationale for Utilizing Minor Element Concentrations to Evaluate Shell Alteration: Oxygen and carbon stable isotopes ratios recovered from mollusk shells are commonly used to reconstruct paleotemperature. Molluscan shells are used because they tend to be relatively common, are less susceptible to diagenetic alteration than bone apatite or bulk samples of rock because of their lower porosity (Constantz, 1986), generally secrete their shells in isotopic equilibrium with seawater (e.g., Bettencourt and Guerra, 1999; Ivany et al., 2003) and may be compared to Recent relatives or analogs to make paleoenvironmental inferences. In addition, the accretionary nature of molluscan growth makes sclerochronology, the focus of Chapter 3, possible. In mollusks, the 18O ratio is interpreted as a reflection of paleotemperature, once adjustments have been made to account for the 18O ratio of the ambient waters, which is a function of temperature, salinity, and, during icehouse intervals, the volume of water entrained in ice caps (Wright, 1987). Temperature decreases with heavier 18O ratios in aragonitic shell according to the equation: T = 21.8 4.69( 18O arag 18O w) (1) This equation uses isotopic ratios in terms of the Pee Dee Belemnite (PDB) standard (Grossman and Ku, 1986). The 13C ratio depends on temperature, salinity, and the isotopic composition of dissolved inorganic carbon in the system (Grossman and Ku, 1986). Dissolved inorganic carbon is isotopically heaviest near the surface, due to
14 preferential uptake of 12C by phytoplankton, and lightest in seafloor sediment pore waters. As temperature increases, the difference between the isotopic signatures of the molluscan shell and dissolved inorganic carbon (the carbon isotope enrichment) decreases in a linear fashion. Because the 13C ratio of dissolved inorganic carbon is isotopically heavier than the 13C ratios of molluscan shell, this means that at higher temperatures, heavier 13C ratios result (Grossman and Ku, 1986). Carbon isotope ratios in molluscan shell may be modified from seawater 13C by exchange with metabolic CO2, which tends to have an isotopic signature of -40Â‰ to -30Â‰, as evidenced by the trend toward lighter 13C ratios in the muscle scar regions of the Nautilus shell (Auclair et al., 2004). There has also been also a metabolic effect documented for mollusks with respect to 18O, with greater variation in 18O for the surf clam Spisula (Ivany et al., 2003) during early ontogeny, and for the abalone Haliotis when rapidly repairing injured shell (Epstein et al. 1963). This effect may also be present in Baculites (Fatherree et al. 1998) and Eutrephoceras (Landman et al., 1983). A positive correlation between 18O and 13C suggests metabolic discrimination against heavier isotopes, while a negative correlation could indicate increased productivity due to higher temperatures (Mitchell et al., 1994). In some mollusks, such as Strombus and Baculites with the onset of maturity, 13C and 18O trend simultaneously toward heavier values (Fatherree et al., 1998; Herbert, pers. comm., 2006). During spawning, shell precipitation slows (Elliot et al., 2003), so isotopic records are biased towards the temperatures of water when the organism is not spawning. Thus, a mollusk that spawns in summer may show mostly moderate and cold temperatures in its sclerochronologic record. A mollusk that spawns in summer but ceases precipitation of shell when
15 temperatures are below a certain threshold, which is reached in winter months, will show moderate temperatures. When estimating paleoceanographic conditions from stable isotopes in fossil shell, it is imperative that the observed variation in the stable isotopes is due to paleoenvironment and/or metabolism, rather than post-depositional alteration. Defining Â“unalteredÂ” shell presents a challenge to paleontologists and geochemists. Alteration may include dissolution and recrystallization. One sign of dissolution is the presence of holes in the individual crystals of the shell; another is the rounding of their edges (Buchardt and Weiner, 1981; Schmidt, 1997). Recrystallization produces a Â“blockyÂ” crystal texture (Schmidt, 1997) or fusion of individual aragonitic platelets (Buchardt and Weiner, 1981). Mineralogical impurities may also grow upon or adsorb to the shell. Common mineralogical impurities include the calcite spar and gypsum crystals appearing on ammonite shell witnessed by Buchardt and Weiner (1981), the pyrite noted by Landman et al. (1983) in Eutrephoceras shell, and the chert and rhombohedral calcite crystals observed by Elorza and Garca-Garmilla (1996) in the void spaces of Inoceramus shell. Minor element analysis measures the concentration of chemical elements within the shell. Some elements, such as Fe, Mg, Mn, and Sr, substitute into the crystal lattice of aragonite or calcite. Others, such as K and Na, either reside in interstitial spaces in the crystal lattice or adsorb to its exterior (Dodd, 1967). Analyses are usually performed on an electron microprobe or an ICP system The electron microprobe detects X-ray radiation produced when electrons bombard a thin section, while the ICP-OES system detects the wavelength of radiation produced by interaction of a plasma beam with
16 cations in solution. Minor element analysis was selected for this study because: 1. Minor element analysis has the potential to reveal the source of alteration, such as exchange with meteoric water or precipitation of secondary cements; 2. The concentrations of minor elements, particularly Mg, K, Na, and Fe, may be altered in shells that show no evidence of recrystallization (Ragland et al. 1979); 3. A large body of molluscan minor element data exists for comparison (e.g., Brand, 1986; Pagani and Arthur, 1998;Dutton et al., 2002); and 4. The minor elements of Sr, Mg, and Na have experimentally determined relationships with temperature and salinity that may be applicable to this study. Because the only elements of interest are cations that substitute into the aragonite crystal structure or form the cations of secondary minerals, the ICP-OES method was selected. Seven elements were then selected for, based upon prior research: aluminum, potassium, iron, manganese, magnesium, sodium, and strontium. 2.1.2. Studies Utilizing Minor Elements as a Proxy for Shell Alteration: Concentrations of potassium and sodium are believed to reflect seawater compostion. White (1979) established that mollusks coprecipitate potassium and sodium in equilibrium with seawater (as cited in Brand, 1986). In the oyster Crassostrea there is a statistically significant linear correlation between salinity and sodium concentration in the precipitated shell (Rucker and Valentine, 1961). Sodium content in Crassostrea valves is ~3000 ppm for seawater of normal salinity, but is ~2500 ppm for seawater with a salinity of 15Â‰. The salinity-sodium relationship is supported by the presence of similar Na/Ca ratios among different genera of ammonites that presumably lived in the same vertical level of the water column (Whittaker et al., 1986). However, whether the
17 Na/Ca ratio in cephalopod mollusks reflects true salinity may be debatable. There is no correlation between Na/Ca and stable isotopes in the Whittaker et al. (1986) study, which are influenced, albeit indirectly, by salinity. Of course, the study location (in the centernorth of the Western Interior Seaway) may not have experienced sufficient salinity fluctuations to produce fluctuations in Na/Ca. Of more concern is a minor-element analysis of Recent Nautilus which found a discrimination factor of 2:1 for sodium, indicating a preference for sodium accumulation in the shell versus the concentration in seawater (Brand, 1983). These findings, howev er, have not been corroborated by study of other Nautilus species (Mann, 1992). Brand (1986) also describes a non-linear relationship between salinity and sodium in Recent and fossil aragonitic mollusks: S = -5.769ln(A) + 28.380 (2) Salinity S is given in parts per thousand 0.5, and A is the ratio of ppm Sr / ppm Na, or the geometric mean of such ratios. The use of strontium is empirically derived, and appears to correct for the genus-level variation in Na discrimination. Strontium and, to a lesser extent, sodium may be depleted during diagenesis; other elements which are typically enriched during diagenesis can be used to identify specimens that could produce questionable paleosalinities. The elements manganese, magnesium, and iron are all present in meteoric water at 2-4 times the level of seawater, so can be used as proxy for diagenetic alteration by exchange with meteoric water (Veizer and Fritz, 1976). For unaltered specimens, the covariance of magnesium with sulfur in the bivalve Mytilus edulis suggests that the organic matrix contains a significant amount of magnesium (Rosenburg and Hughes, 1991). Higher magnesium concentrations are also correlated with faster shell precipitation in this bivalve, suggesting variation of the element with
18 metabolism. The average concentrations of magnesium in molluscan shell vary significantly by taxonomic class (Turekian and Armstrong, 1960) and by species in Nautilus (Mann, 1992). The strontium concentration of aragonitic molluscan shell has been correlated with many different environmental and physiological factors. A decrease in strontium, for instance, has been correlated with all of the following: 1) A decrease in salinity along an exponential relationship that can be approximated as linear above salinities of 20Â‰. This trend is based on values from a variety of Recent aragonitic bivalves and gastropods, compiled by Dodd and Crisp (1982). 2) An increase in salinity for individual Neomidion bivalves living in a Jurassic estuary (Holmden and Hudson, 2003). 3) A slowing of growth rate and/or metabolic effects in the Eocene bivalve Venericardia and gastropod Clavilithes (Purton et al. 1999). 4) Species-specific differences, rather than environmental or phylogenetic gradients, as in Recent Nautilus 5) A decrease in the 18O ratio, implying an increase in temperature and the potential utility of strontium in paleothermometry for the Antarctic Eocene bivalve Cucullaea (Dutton et al. 2002). 6) A decrease in visually assessed shell quality (Buchardt and Weiner, 1981), and percent aragonite (Hallam and Price, 1966),indicating alteration. All of these trends are superimposed on a ~1:5 discrimination factor for strontium
19 concentrations in seawater versus strontium concentrations in the aragonite of bivalves, gastropods, and Nautilus (Turekian and Armstrong, 1960; Brand, 1983). Very little research done has been on aluminum concentrations in molluscan shell, perhaps because the concentrations are low, approaching the detection limits of the analytical techniques (Brand, 1983). Brand (1983) found that Nautilus shell contains 030 ppm of aluminum. Unaltered inoceramid shell, according to Elorza and GarcaGarmilla (1996), is ~0.2% Al2O3. Given the paucity of information about aluminum, this study will significantly add to the existing data on this element. By far the most extensive data has been collected on magnesium and strontium concentrations, and these elements display complex, various relationships for different mollusks. With additional research, such complexities may be revealed for other minor elements included in molluscan shell. 2.2 Methods 2.2.1 Selection of Samples: Samples for the fossil shell alteration investigation were taken in groups, here called Â“suites,Â” that each addressed particular multiple working hypotheses. The hypotheses, taken primarily from previous research on shell preservational issues in Western Interior Seaway fossils, are as follows: (1) Shell preserved directly in shale will be more pristine than shell preserved in concretions, which may be chemically altered during the dissolution and precipitation associated with concretion formation. An alternative hypothesis is that shell preserved within concretions will be less altered than shell preserved in shale, because the concretion is impermeable to groundwater. (2) Ammonite phragmacone will be less altered than ammonite septa, because of
20 the tendancy for cements to form in the interior of the ammonite shell. An alternative hypothesis is that ammonite phragmacone will be more altered, because it is on the exterior of the shell and could thus be exposed to more groundwater and/or surface water. (3) Shell that is white to beige in color, with iridescent nacre, will be the most pristine. As in Recent molluscan shells, slight variation in color from that noted above may indicate optimal preservation for different genera. (4) Molluscan shell will have distinct minor element and isotopic signatures from the surrounding matrix (shale, siltstone, or concretion), and from crystalline cements precipitated within the shell. Progressively more diagenetically altered shell material will have minor element and isotopic signatures intermediate between unaltered shell and the cement itself. (5) Isotopic signatures will cluster by genus, and allow for a classification of mollusks as inhabiting deep-water, intermediate-water, or surface-water masses. Certain heteromorph ammonites may display two modes of life, changing habitat during ontogenetic changes in morphology. (6) Isotopic signatures will display a shift between Kremmling, Colorado, specimens and Trask and Game ranches, South Dakota, specimens, due to differences in temperature and/or salinity. To test hypothesis 1, a Â“Mode of PreservationÂ” suite was developed. This suite included specimens of the same genus ( Placenticeras Inoceramus Baculites and Nymphalucina ) preserved in shale and calcareous concretions. Shale-concretion pairs of Baculites and Inoceramus were selected from a single locality: the Game Ranch.
21 Limitations in the collected material meant that this was impossible for all genera, and lithologic pairs had to be constructed using multiple localities. One sample was taken from each of twenty specimens (ten shale-concretion pairs). Care was taken to select specimens for each pair that were similar in color and shell thickness, and sample these at the same point in ontogeny. To address hypothesis 2, a Â“Shell Sampling LocationÂ” suite was developed. This suite included specimens of three ammonite genera ( Placenticeras, Baculites, and Hoploscaphites ). One sample was taken from a septum of each specimen and another from the adjacent phragmacone, for a total of twenty samples. To investigate hypothesis 3, twenty specimens from each locality were analyzed, for a total of sixty specimens in the Â“Shell Color SuiteÂ”. Genera represented included three ammonites ( Placenticeras Baculites and Hoploscaphites ), three bivalves ( Anomia Nymphalucina and Inoceramus ), and two gastropods ( Anisomyon and Drepanocheilus ). Two to five specimens of different shell colors were selected for each genus at each location, depending on available specimens. A single sample was taken from each specimen, at an equivalent point in ontogeny for specimens of each genus. To test hypothesis 4, a 35-specimen Â“Cementation SuiteÂ” was assembled. Of this suite, specimens 1-10 were from Kremmli ng, specimens 11-15 were from Game Ranch, and the remainder were from Trask Ranch. Four types of samples were taken: ammonite phragmacone shell (from Placenticeras Baculites and Hoploscaphites ), matrix (concretion or siltstone), cements precipitated in the cavities of the shell, and calcitic material found on the exterior of the shell. Each specimen contained two or more of these materials, with one sample taken of each material, for a total of 111 samples.
22 For hypotheses 5 and 6, the combined data set was used. As seen in Table 4, this includes over 100 ammonite samples: 59 Baculites samples, 24 Placenticeras samples, and 22 Hoploscaphites samples. The combined data set also contains bivalve samples (18 from Inoceramus 6 from Nymphalucina and 4 from Anomia ) and gastropod samples (2 from Anisonmyon and 3 from Drepanocheilus ). 2.2.2 Treatment of Samples: Three techniques were used to prepare samples for the shell-alteration investigation. Whenever possible, shell was removed intact, using laboratory tweezers and similar implements. Target sample size was the equivalent of a square 2-3 mm on each side. For particularly Â“promisingÂ” specimens Â– ammonites with clean, irridescent shell displaying growth lines and a total shell thickness of 0.5 mm or greater Â– a second, adjacent sample was taken and sent to the American Museum of Natural History for scanning electron microscopy and to SUNY Stony Brook for tstrontium isotopic analysis. When shell could not be removed intact, it was scaped from the specimen using a curved pick, with care taken to sample the entire thickness of shell. Different layers within a shell, due to diffe ring crystal structures, different temperatures at the time of precipitation, and/or metabolic effects at time of deposition, may show different isotopic signatures. For example, the bivalve Pecten shows strongly depleted 18O and 13C in surficial samples relative to samples which included the entire thickness of the shell (Mitchell et al. 1994). In ammonites, differences in isotopic composition with respect to sampling location have been shown for Baculites compressus (Forester et al. 1977; Fatherree et al. 1998). Surficial recrystallization or cement samples were scraped from the shells they were preserved upon. Cement and concretion samples were taken using a Dremel variable-speed drill fitted with a diamond-coated bit. All
23 specimens were ground into a uniform fine powder using a mortar and pestle, made of agate to minimize contamination. 2.2.3 Mass Spectrometer Analysis: Subsamples of 60-100 g were measured on a microbalance into small glass vials. These specimens were dried in a laboratory oven at 70 oC for at least one week to remove moisture. The specimens were transferred to reaction vials for a target mass of 35-80 g, which were then reacted with 100% phosphoric acid added to each reaction vial within the carbonate preparation device of the mass spectrometer. The mass spectrometer used in this study is a ThermoFinnigan Delta Plus XL dual inlet mass spectrometer with an in-line Kiel III Carbonate Preparation Device, and resides at the Center for at the College of Marine Sciences, University of South Florida, St. Petersburg, Florida. Six replicates of the NBS19 standard, taken as 13C = 1.95Â‰ and 13C = -2.20Â‰ with respect to PDB, were included in each mass spectrometer run to determine the analytic uncertainty. Analytical uncertainty, at the 95% confidence level, was 0.03Â‰ for the 13C values and 0.08Â‰ for the 18O values. Data from samples producing a signal of less than 600mv, which usually results from carbonate mass <20 g, were discarded and, when possible, rereun. All values are reported with respect to the Pee Dee Belemnite. 2.2.4 ICP Analysis: Sub s amples of 100-200 g were placed directly into polyethylene tubes used for the analysis. Once all the samples were prepared, 2.0 mL of 2% HNO3 was added and the samples were inverted to ensure the entire sample dissolved. The Perkin Elmer Optima 4300DV dual view ICP-OES, housed at the same facility as the mass spectrometer, was calibrated with a series of four serially diluted multi-element concentration standards, commercially available from SCP-Science. All
24 minor element samples were run as a single batch to minimize analytical uncertainty, which was better than 1% relative standard deviation for all values. Table 5 lists the detection limits for the elements focused upon in this study. 2.2.5 Data Processing: Minor element concentrations were received in parts per million (ppm) and converted to atomic ratios with respect to calcium. The ratios, given in mMol/Mol Ca, were obtained by dividing the weight percent of the minor element, divided by its atomic mass, by the weight percent of calcium, divided by its atomic mass. All statistical calculations were performed with the minor element ratios, but the concentrations of minor elements in ppm were needed for paleosalinity calculations using equation 2. This equation for paleosalinity, from Brand (1986), was selected because it was derived for both gastropod and bivalve mollusks, from a variety of habitats, fossil and Recent. A correction factor, derived from data on Recent Nautilus in the wild, was applied to the equation to compensate for the higher concentrations of sodium in cephalopods than bivalves or gastropods living in the same habitat (Dodd, 1967). Stable isotope concentrations were received in per-mil notation, with respect to the Pee Dee Belemnite (PDB) standard. A value of 18O = -5Â‰ means that the shell has a 5Â‰ lighter 18O ratio than the PDB standard; i.e., it has a greater proportion of 13C than the standard. Paleotemperature was calculatied using equation 1, Grossman and KuÂ’s molluscan aragonite temperature correlation.after first applying to determine the 18O value of the waters surrounding the mollusk using Equation 3: S(WIS) = [1 Â– ( w(WIS)w(ocean)))/( f w(ocean))] x S(ocean) (3) Constants for 18O of the open ocean were w(ocean) = -1.22Â‰ PDB and S(ocean) = 34.3, values calculated from models of Earth without polar ice caps (Schmidt, 1997).
25 Grossman and KuÂ’s equation is likewise appropriate because all molluscan shell samples used in this study, with the exception of calcitic Anomia for which no unaltered specimens were found, were aragonitic. Inoceramus which contains both a prismatic calcitic layer and aragonitic nacreous layer, was sampled only in the aragonite.
26 TABLE 4-Specimen Suites Used in Shell Alteration Investigations Mode of Preservation Suite Shell Testing Location Suite Shell Color Suite Cementation Suite Total Number of Samples Baculites phragmacone 5 7 15 25 52 Baculites septa 7 7 Placenticeras phragmacone 6 2 10 4 22 Placenticeras septa 2 2 Hoploscaphites phragmacone 1 11 9 21 Hoploscaphites septa 1 1 Inoceramus shell 5 13 18 Nymphalucina shell 4 2 6 Anomia shell 4 4 Anisomyon shell 2 2 Drepanocheilus shell 3 3 Concretion 34 34 Cementation 33 33 Exterior Crystallization 6 6 Total Number of Samples 20 20 60 111 211 The 211 samples investigated in the shell alteration portion of this study are divided into four suits, each with its own hypothesis to test Because the focus of most hypotheses is on ammonites, they are overrepresented in the dataset compared to Inoceramus the only numerous bivalve genus for the sampling locations. Nonetheless, a variety of genera are represented by the combined dataset.
27 TABLE 5 Â– Limits for ICP-OES System. Al Ca Fe K Mg Mn Na Sr Wavelength, nm 396.153 315.887 238.204 766.490 285.213 257.610 589.592 407.771 Detection Limit (ppm) 1.60 5.87 0.35 0.39 0.38 0.05 1.08 0.01 Limit of Quantitation (ppm) 5.35 19.56 1.17 1.29 0.68 0.16 3.53 0.03 Limits of quantitation for the ICP-OES system used in this study were approached for analyses of Fe, Mn, Mg, Sr, and Al. These values are the concentrations below which no numerical data analysis should be performed. All data with minor element concentions below the limit of quantitation were omitted from statistical analyses and regression trendlines. Limits of detection express how much of the element must be present in the sample to produce results. This threshold was crossed most frequently with Al.
28 2.3 Results 2.3.1 Mode of Preservation: Results for the Â“Mode of PreservationÂ” suite were obtained for all twenty samples (see Appendices A and B). As Figure 2 displays, most of the samples cluster with 18O ratios ranging from 0.50Â‰ to 5.00Â‰, with respect to PDB. The 13C values range from -5Â‰ to 6Â‰. The Nymphalucina preserved in a Trask Ranch concretion is an exception with 18O = -9.07Â‰ and 13C = -13.0Â‰. Likewise, the Placenticeras samples from Kremmling, Colorado, concretions were anomalous with 18O ranging from -15Â‰ to -20Â‰ and 13C from -7.44Â‰ to -3.99Â‰. In total, four of the five outliers were samples from concretions. A t-test of independent samples with level of significance = 0.05 reveals significantly lighter 18O in concretions and a strong relationship between concretions and lighter 13C values (Table 6). These statistical findings support the visual observation that, within the cluster of shell samples on the isotope cross-plot, there appears to be no pattern in the relative position of shale and concretion points. Within the cluster of stable isotope data, the Inoceramus samples show the isotopically heaviest carbon signature (mean 13C = 3.47 2.44Â‰), along with the isotopically lightest oxygen signature (mean 18O = -3.38 1.31Â‰). The Inoceramus found in Trask Ranch concretions had an isotopic signature closer to the Inoceramus found in Game Ranch shale than Game Ranch concretions. Conversely, the Baculites samples show the isotopically lightest carbon signature (mean 13C = -0.73 1.30Â‰), along with the isotopically heaviest oxygen signature (mean 18O = -1.34 1.09Â‰). The Baculites found in Trask Ranch concretions had isotopic signatures closer to the Baculites found in Game Ranch concretions than Game Ranch shale. The Placenticeras samples have similar carbon values (mean 13C = -1.43
29 0.43Â‰) as the Baculites but intermediate oxygen values (mean 18O = -2.58 1.19Â‰) between the points for Baculites and Inoceramus specimens. While there are only two points for Nymphalucina they are closest to the light-carbon, heavy-oxygen Baculites As in the isotopic data, in the minor element data, the outliers were from concretions. All minor element concentration data shown in Figures 3 and 4 is expressed in mMol/Mol ratios with calcium. The Kremmling Placenticeras and the Trask Ranch Nymphalucina represent outliers depleted in strontium and enriched in magnesium relative to Recent mollusks (Figure 3). An Inoceramus shell sample was slightly enriched in magnesium (3.44 mMol/Mol) and a Baculites sample from Trask Ranch was enriched in both strontium and magnesium relative to Recent aragonitic shell material (Buchardt and Weiner, 1981). Figure 4, a pair of radar charts, depicts minor element concentrations for all elements examined. Each axis of a chart records the concentration of an element, in mMol/Mol, with lines connecting all data points for a given sample. Enrichment outliers for aluminum, iron, manganese, and strontium were present for the concretion samples, but not for the shale samples (however, in the latter, no aluminum concentration data could be obtained due to c oncentrations below the analytical detection level). The outliers belong to four different samples, rather than to one sample that was highly altered. In both concretions and shale, the mean K/Ca ratio was ~0.8 mMol/Mol, Na/Ca ratio was ~16 mMol/Mol, and Sr/Ca ratio was ~3 mMol/Mol. The concretions had higher mean Fe/Ca ratios (8.3 1.4 mMol/Mol vs. 1.12 1.06 mMol/Mol), Mn/Ca ratios (5.1 2.4 vs. 1.69 1.23 mMol/Mol), and Mg/Ca ratios (6.2 0.9 vs. 0.88 0.94 mMol/Mol). The differences in magnesium and iron were the only statistically significant trends in the minor isotope ratios, as evaluated by one-tailed t-tests of
30 independent samples, 0.05 level of significance, reported in Table 2. The lower mean concentration of manganese in the shale samples was nearly significant, with t = -1.7 (critical t = -1.753) and the higher mean concretion of sodium in the shale samples was also nearly significant, with t = 1.4 (critical t = 1.746).
31 FIGURE 2 Â—Mode of Preservation Stable Isotope Cross-Plot The plot of oxygen and carbon stable isotopes for the Â“Mode of PreservationÂ” shell alteration suite, with color denoting genus and symbol type denoting location, clearly shows outlier data points for specimens preserved in concretions.
32 TABLE 6 Â—Summary Statistics for Mode of Preservation Suite Alternate Hypothesis Type of Test N Mean, standard deviation Calculated Value(s) Critical Value (95% confidence) Result Significantly lighter mean 13C in concretions? One-tailed ttest (independent samples) 9s, 11c s: -1.28 6.81 c: -2.74 5.07 t = 1.35 t = 1.75 Ho retained Significantly lighter mean 18O in concretions? One-tailed ttest (independent samples) 9s, 11c s: -2.04 1.78 c: -6.60 6.74 t = 4.76 t = 1.75 Ho rejected Significantly lower mean Fe/Ca in shale? One-tailed ttest (independent samples) 6s, 11c s: 1.12 1.06 c: 8.3 1.4 t = -2.0 t = 1.753 Ho rejected Significantly lower mean K/Ca in shale? One-tailed ttest (independent samples) 9s, 11c s: 0.731 0.855 c: 0.93 0.20 t = -0.64 t = 1.746 Ho retained Significantly lower mean Mg/Ca in shale? One-tailed ttest (independent samples) 9s, 11c s: 0.88 0.94 c: 6.2 0.9 t = -2.8 t = 1.746 Ho rejected Significantly lower mean Mn/Ca in shale? One-tailed ttest (independent samples) 6s, 11c s: 1.69 1.23 c: 5.1 2.4 t = -1.7 t = 1.753 Ho retained Significantly higher mean Na/Ca in shale? One-tailed ttest (independent samples) 9s, 11c s: 17.2 4.1 c: 14.0 3.0 t = 1.4 t = 1.746 Ho retained Significantly higher mean Sr/Ca in shale? One-tailed ttest (independent samples) 9s, 11c s: 2.85 1.69 c: 3.4 0.74 t = -0.43 t = 1.746 Ho retained Summary statistics for the Â“Mode of PreservationÂ” Suite show significantly lower Mg/Ca ratios in specimens preserved in shale and significantly lighter 18O in specimens preserved in concretions. The null hypothesis, that there is no significant difference in the mean between shale and concretion subsets, was retained for all other tests. All isotope ratios reported in Â‰ versus PDB and all minor element ratios reported in mMol/Mol calcium.
33 FIGURE 3 Â–Sr/Ca and Mg/Ca Ratios for Â“Mode of PreservationÂ” Suite In the Sr/Ca-Mg/Ca minor element cross-plot, the majority of data points residing outside of the field for Recent aragonitic shell are from specimens in concretions. These points are enriched in magnesium relative to Recent aragonitic shell.
34 FIGURE 4 Â–Radar Charts for Minor Element Concentrations in the Â“Mode of Preservation SuiteÂ” The minor element ratios for the concretion specimens show enrichment in iron, magnesium, and manganese relative to those taken from shale.
35 2.3.2 Shell Sampling Position : Minor element concentrations for the Â“Shell Sampling PositionÂ” suite were obtained for all twenty samples (ten phragmacone-septum pairs). Stable isotope results were obtained for eighteen of the samples (see Appendices A and B), with septum specimen 3S and phragmacone samples 2P unreliable, and therefore omitted, due to low mass spectrometer voltage, possibly from underweight samples. These results may be seen in tabular form within Appendices A and B. In the stable isotope cross-plot (Figure 5), the data cluster by genus. The Placenticeras had the isotopically heaviest 13C and the isotopically lightest 18O, with -3.71Â‰ and -3.74Â‰, for the septum, and -2.91Â‰ and -2.67Â‰ for the phragmacone, respectively. The Hoploscaphites had a similar 18O, but lighter 13C, with -3.69Â‰, -8.36Â‰ for the septum, and -3.64Â‰ and -7.46Â‰ for the phragmacone, respectively. The isotopic signatures of the Baculites samples vary greatly, with mean 13C and 18O values of -6.22 4.13Â‰ and -1.36 2.35Â‰, respectively. The values recorded from each specimen often proved vastly different. Three phragmacone and septum pairs (the Hoploscaphites and two Baculites specimens from the Trask Ranch) do have similar isotopic values; the remaining seven do not. These pairs were analyzed using a statistical paired t-test for dependent samples, as shown in Table 7. At the 0.05 significance level, the difference in 13C between septum and phragmacone samples taken from the same specimen may be explained by random chance. The difference in mean 18O is significant at the 0.05 level, with 18O from the phragmacones lighter than those from the septa. It should be noted that the mean 13C value is influenced by a Trask Ranch Baculites phragmacone sample, at the bottom of Figure 6, which is a statistical outlier with respect to the other phragmacone samples.
36 When the septum-phragmacone pair containing this point is removed, the t-score for the 13C ratio increases, indicating a greater difference between phragmacone and septal samples, while the 18O ratio decreases below the 0.05 level of statistical significance. In addition, the 13C ratio of the phragmacone samples increases from -5.09 4.41Â‰ to 3.72 2.29Â‰ and the 18O ratio of the phragmacone samples increases from -7.03 2.96Â‰ to -6.73 3.07Â‰. While the statistical dependence of the samples upon each other precludes the ability to apply a t-test to the data subsets consisting of all phragmacone and all septal samples, it is clear from the means and the distribution of points in Figure 5 that the septal samples tend to have lower 13C values. In the graph of Sr/Ca versus Mg/Ca ratios (Figure 6), only two data points fall within the limits established for Recent aragonitic shell. These points are both phragmacone samples: one a Placenticeras from Game Ranch and the other a Hoploscaphites from Trask Ranch. The septum of the aforementioned Placenticeras is an outlier strongly enriched in strontium (Sr/Ca = 16.4 mMol/Mol), while all other samples have Sr/Ca ratios between 2 and 5 mMol/Mol, values on the lower end of the range for Recent aragonitic shell. There is no difference between Sr/Ca ratios between corresponding septal and phragmacone samples to the 0.05 level of significance with a two-tailed t-test of dependent samples (Table 7). Likewise, there is no significant difference in Mg/Ca ratio, though in this instance the t-score is much higher (t = -1.9 versus critical t = 2.262). The greater t-score is expected because of the high standard deviation of the Mg/Ca ratios within the Â“Shell Testing LocationÂ” suite and the large span of data points along the y-axis of Figure 6. Most of the data points in the suite are relatively enriched in magnesium, up to Mg/Ca = 48.9 mMol/Mol, without any statistical
37 outliers. Statistical outliers do exist for the Fe/Ca, Na/Ca, and Sr/Ca ratios of the Kremmling, Colorado, Placenticeras sample, the first two ratios for both phragmacone and septum and the last ratio for the septum alone. Another outlier was the enriched Sr/Ca of the Game Ranch Placenticeras septum. These outliers may be seen graphically as the endpoints on the radar diagrams in Figure 7. Interestingly, the Placenticeras data that contain the statistical outliers also show the greatest mismatch between the chemical content of phragmacone and septal samples within a pair. All other pairs show similar chemical profiles, with peaks greater than 5 mMol/Mol for magnesium, sodium and, for the Colorado specimens and South Dakota Hoploscaphites manganese. Small peaks, with concentrations less than or equal to 10 mMol/Mol Ca, also occur for iron in the South Dakota specimens. When the large Fe/Ca ratio of the Kremmling Placenticeras is removed from the data, a statistically significant difference in the Fe/Ca ratio for phragmacone-septum pairs emerges. Figure 7 reveals the difference to be a relative enrichment of iron for the septal samples. Comparing the differences in isotopic ratios to the minor element data, several trends emerge. First, specimens with enriched magnesium and/or manganese -such as the Game Ranch Placenticeras and the second, third, and fourth Trask Ranch Baculites Â– also had large differences between the isotopic signatures of their septa and phragmacones. However, the Trask Ranch Hoploscaphites specimen was enriched in magnesium but did not display a substantial difference between phragmacone and septal isotopic signatures and the fifth Trask Ranch Baculites specimen showed a fairly wide span of values on the isotope cross-plot without high magnesium or manganese
38 concentrations. The similarity in minor element distributions (overall shape of the radar chart polygon) is a better predictor of isotopic similarity than the numeric concentrations of minor elements. The best matches, as seen in Figure 7, are the Trask Ranch Hoploscaphites and the first and sixth Trask Ranch Baculites and these are also the pairs that are closest together on the isotope cross-plot. The poorly-matched septal and phragmacone samples of the Game Ranch Placenticeras specimen correlate with a moderately high difference in 13C and 18O. The Trask Ranch Baculites samples that were isotopically different had the same minor element distribution, with peaks in Fe, Mg, and Na, but the phragmacone and septal samples within a pair differed in their concentrations of these elements. Unfortunately, no isotopic data was available for the Kremmling specimens, which matched poorly in minor element distribution and would have provided useful comparisons.
39 FIGURE 5 Â—Shell Sampling Position Stable Isotope Cross-Plot This plot shows oxygen and carbon stable isotopes for the Â“Shell Sampling PositionÂ” shell alteration suite, with color denoting genus, symbol shape denoting location, and symbol fill denoting septum versus phragmacone sampling. Quite frequently, phragmacone-septum pairs are isotopically different from each other.
40 TABLE 7 Â–Summary Statistics for Â“Shell Sampling PositionÂ” Suite Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value(s) Critical Value (0.05) Result Difference in 13C values of septumphragmacone pairs? Paired t-test (dependent samples) 8s, 8p 6s, 6p p: -5.09 4.41 s: -7.03 2.96 Without outlier: p: -3.72 2.29 s: -6.73 3.07 t = 1.21 t = 1.77 t = 2.365 t = 2.571 Ho retained; Ho retained Difference in 18O values of septumphragmacone pairs? Paired t-test (dependent samples) 8s, 8p 6s, 6p p: -2.35 0.74 s: -2.92 0.82 Without outlier: p: -2.42 0.77 s: -2.91 0.89 t = 3.04 t = 2.02 t = 2.365 t = 2.571 Ho rejected; Ho retained Difference in Al/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 8p, 8s 7s, 7p p: 4.633 4.579 s: 6.047 6.200 Without outliers: p: 2.960 1.921 s: 4.318 2.428 t = -12.82 t = -7.590 t = 2.365 t = 2.447 Ho rejected; Ho rejected Difference in Fe/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 6.1 11.5 s: 8.6 7.4 Without outliers: p: 2.80 3.05 s: 5.64 2.51 t = -1.3 t = 2.64 t = 2.262 t = 2.571 Ho retained; Ho rejected Difference in K/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 0.07 0.03 s: 0.1 0.2 Without outliers: p: 0.07 0.02 s: 0.07 0.03 t = -1 t = 0.8 t = 2.262 t = 2.306 Ho retained; Ho retained Difference in Mg/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 14.5 13.9 s: 20.4 10.5 Without outliers: p: 15.7 14.8 s: 21.5 10.5 t = -1.9 t = -1.5 t = 2.262 t = 2.306 Ho retained; Ho retained Difference in Mn/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 4.3 5.7 s: 5.5 4.0 Without outliers: 3.5 4.9 4.8 4.2 t = -1.16 t = 1.81 t = 2.262 t = 2.306 Ho retained; Ho retained Difference in Na/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 19.8 12.6 s: 22.7 11.9 Without outliers: p: 22.2 12.7 s: 21.9 12.4 t = -0.55 t = 0.050 t = 2.262 t = 2.306 Ho retained; Ho retained Difference in Sr/Ca of septumphragmacone pairs? Paired t-test (dependent samples) 10p, 10s 8p, 8s p: 2.69 1. 21 s: 6.1 6.5 Without outliers: p: 2.83 1.14 s: 3.10 1.04 t = 1.6 t = 0.855 t = 2.262 t = 2.306 Ho retained; Ho retained Significant relationships exist for 18O, Al/Ca, and Fe/Ca. For other tests, the null hypothesis of no difference in means between septa and phragmcones is retained. All isotope ratios reported in Â‰ versus PDB; all minor element ratios reported in mMol/Mol.
41 FIGURE 6 Â—Shell Sampling Position Sr/Ca-Mg/Ca Cross-Plot Very few of the samples for the Â“Shell Sampling PositionÂ” suite fall within the Mg/Ca and Sr/Ca limits for Recent aragonitic shell. As in the isotopic data, the phragmacone and septum samples may differ in their chemical composition.
42 FIGURE 7 Â—Radar Charts for Minor Elements in Â“Shell Sampling PositionÂ” Specimens Most phragmacone-septum pairs share patterns in minor elements though amounts differ.
43 2.3.3 Shell Color Suite: Two aspects of shell color were investigated in this study: the presence or absence of an opalescent luster and the color of the shell. A suite of 60 specimens was assembled, with 20 samples per collection site and representatives of all genera (see Appendices A and B). For each genus at each location, specimens of at least two different colors were sampled. Twelve samples, including representatives of Placenticeras Baculites Hoploscaphites and Inoceramus could be classified as opalescent. These genera were also represented in non-opalescent shell, along with additional genera Nymphalucina Anomia Drepanocheilus and Anisomyon All genera in the study were thus represented in the Â“Shell ColorÂ” suite. As Figure 8 illustrates, the majority of the samples from opalescent shells, including those from the opalescent 10YR3/6, opalescent 5Y8/9, opalescent 7.5YR6/7, and opalescent N9 color classes cluster between 13C values ranging from 5Â‰ to -5Â‰ and 18O values spanning 0Â‰ to -4Â‰ (See Table 8 for color designations). A single outlier is the Kremmling Placenticeras sample, with 18O and 13C values of -15.01Â‰ and -6.99Â‰, respectively. The non-opalescent shell samples show a greater range of values, but tend to cluster into two subsets as defined by 18O. All of the members of the relatively 18O-depleted cluster are from Kremmling (whereas only two members of the relatively 18O-enriched cluster are). Therefore, the Colorado and South Dakota specimens were separated during statistical analysis (Tables 9 and 10). The 13C and 18O averages became heavier when the Kremmling points were removed, with an opalescent shell 13C average of -2.08 2.47Â‰ (versus -3.43 3.97Â‰ when including Kremmling data) and 18O average of -1.53 1.95Â‰ (versus -2.27 1.04Â‰). The non-
44 opalescent shell 13C average was -1.64 5.71Â‰ (versus -3.07 5.38Â‰ when including Kremmling data), and the 18O average was 3.61 1.87Â‰ (versus -6.98 5.22Â‰). In most instances, the standard deviation also decreases when the Kremmling data is removed, though this effect is more marked for the oxygen than carbon data. The onetailed t-tests for independent samples calculated for the opalescent and non-opalescent shell reveal no significant differences in the 18O or 13C ratios. The extremely low 13C t-score (0.011) for the South Dakota data suggests that the variation in the data was caused by the difference between South Dakota and Colorado isotopic signatures. However, the t-score for 18O is greater, indicating that opalescent shell has heavier 18O, but not at a level of statistical significance. Indeed, in Figure 8, the opalescent samples, designated by square boxes, tend to cluster towards heavier 18O. When examining the minor element ratios with respect to shell opalescence, few important results emerged. Using one-tailed t-tests at the 0.05 significance level, lower mean Mg/Ca, Mn/Ca, and Sr/Ca ratios were found for the opalescent shell of the full dataset. Another relatively strong relationship existed for higher Sr/Ca ratios in the opalescent shell. These conclusions were not true for the data subset containing only South Dakota collection sites so likely reflect the contribution of the Kremmling samples to the non-opalescent shell, which dominate the low-Sr/Ca, high-Mg/Ca region of the Sr/Ca-Mg/Ca plot shown as Figure 9. The opalescent shell instead resides below or near the Mg/Ca limit for Recent aragonitic shell, and shows little Sr/Ca depletion. When the isotopic and minor element data are examined to see if groupings defined by shell color contributed to variation in the data, most null hypotheses cannot be statistically rejected, both in the complete and South Dakota datsets (Table 10). There
45 are statistically significant differences in mean K/Ca and Mn/Ca for the South Dakota dataset, and a difference in Mg/Ca for both datasets. Statistically insignificant but notable relationships include the differences in 18O (F = 1.94 versus critical F = 2.071), Al/Ca (F = 2.26 versus critical F = 2.477), and Sr/Ca (F = 1.59 versus critical F = 2.044), all for the complete datasets. Among the South Dakota specimens, the highest insignificant F-statistic was Na/Ca (F = 1.6 versus critical F = 2.321). A graphical analysis of color with respect to genus is presented in Table 11. There is a degree of variability for colors in unaltered shell (with Â“unalteredÂ” here defined as shell bearing Sr/Ca and Mg/Ca ratios analogous to Recent aragonitic shell). For instance, Inoceramus may display one of many colors (10YR8/1, 7.5YR8/2, opalescent N9, and 7.5YR9/2), whereas Hoploscaphites has a much narrower range of colors (10YR6/7, and sometimes 10YR7/8). Examining the isotope and minor element cross-plots, darker colors are associated with Inoceramus and Hoploscaphites whereas lighter colors are associated with Baculites and Placenticeras This observation suggests that the color of less-altered shell is influenced by a genus-level trait.
46 TABLE 8 Â–Descriptive Names for Munsell Designations of Shell Color Classes Descriptive Color Class Name Munsell Designation Dark Brown 10YR3/6 Cream 7.5Y9/4 Grey 10YR8/1 Light Grey-Tan 7.5YR8/2 Light Brown 10YR7/8 Orange 10YR7/11 Light Cream 7.5Y9/2 DarkTan 10YR6/7 Light Tan 5Y8/5 White N9 Yellow 5Y8/9 The color descriptive terms used in this paper were selected because they create a more specific mental image of color than the color names associated with the Munsell designations listed above. Approximations of these colors may be seen in the data points in Figures 8 and 9.
47 TABLE 9 Â–Summary Statistics for Â‘Shell ColorÂ’ Suite: Shell Opalescence Alternate Hypothesis Type of Test N Means, std. dev.s Calculated Value(s) Critical Val. (0.05 sig.) Result Lower mean 13C in non-opalescent shell? One-tailed t-test of independent samples 11o, 44n 10o, 28n o: -2.08 2.47 n: -2.82 4.54 South Dakota only: o: -1.58 1.95 n: -1.64 5.71 t = 0.149 t = 0.011 t = 1.674 t = 1.688 Ho retained Ho retained Lower mean 18O in non-opalescent shell? One-tailed t-test of independent samples 11o, 44n 10o, 28n o: -3.43 3.97 n: -6.98 5.22 South Dakota only: o: -2.27 1.08 n: -3.61 1.87 t = 0.765 t = 0.877 t = 1.674 t = 1.688 Ho retained Ho retained Lower mean Al/Ca in opalescent shell? One-tailed t-test of independent samples 5o, 28n 5o, 15n o: 3.47 2.14 n: 5.8 6.2 South Dakota only: o: 2.78 2.52 n: 3.0 2.6 t = -0.73 t = -0.17 t = -1.696 t = -1.734 Ho retained Ho retained Lower mean Fe/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 48n 11o, 29n o: 8.5 11.8 n: 10.5 20.1 South Dakota only: o: 9.3 12.3 n: 9.0 24.9 t = -0.32 t = 0.039 t = -1.672 t = -1.686 Ho retained Ho retained Lower mean K/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 48n 11o, 29n o: 0.07 0.05 n: 0.08 0.07 South Dakota only: o: 0.07 0.05 n: 0.06 0.03 t = -0.5 t = 0.6 t = -1.672 t = -1.686 Ho retained Ho retained Lower mean Mg/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 48n 11o, 29n o: 6.1 8.1 n: 14.1 12.3 South Dakota only: o: 6.6 8.5 n: 13.5 16.4 t = -2.1 t = -1.3 t = -1.672 t = -1.686 Ho rejected Ho retained Lower mean Mn/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 46n 10o, 28n o: 3.4 3.4 n: 7.0 5.5 South Dakota only: o: 4.087 10.065 n: 4.483 4.757 t = -2.1 t = -0.24 t = -1.673 t = -1.688 Ho rejected Ho retained Higher mean Na/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 48n 11o, 29n o: 18.3 14.0 n: 16.0 27.0 South Dakota only: o: 19.9 11.4 n: 20.1 31.6 t = 0.278 t = -0.018 t = 1.672 t =1.686 Ho retained Ho retained Higher mean Sr/Ca in opalescent shell? One-tailed t-test of independent samples 12o, 48n 11o, 29n o: 3.28 0.75 n: 2.35 2.60 South Dakota only: o: 3.57 0.62 n: 3.23 1.62 t = 1.9 t = 0.68 t = 1.672 t = 1.686 Ho rejected Ho retained The null hypothesis, that there is no difference in the means of the opalescent and nonopalescent data sets, holds for most tests in this sampling suite. All isotope ratios reported in Â‰ versus PDB and all minor element ratios reported in mMol/Mol calcium.
48 TABLE 10 Â– Summary Statistics for Â‘Shell ColorÂ’ Suite: Shell Color Alternate Hypothesis Type of Test N Overall means, average standard deviations Calculated Value(s) Critical Value (0.05 significance) Result Difference in mean 13C among shell hue classes? F-statistic 52 34 -3.04 5.45 South Dakota only: -1.63 5.83 F = 0.495 F = 0.443 F= 2.071 F = 2.337 Ho retained Ho retained Difference in mean 18O among shell hue classes? F-statistic 52 34 -6.92 4.40 South Dakota only: -3.65 1.43 F = 1.940 F = 1.345 F= 2.071 F = 2.337 Ho retained Ho retained Difference in mean Al/Ca among shell hue classes? F-statistic 28 15 6.46 4.25 South Dakota only: 4.30 3.95 F = 2.26 F = 1.62 F = 2.477 F = 3.478 Ho retained Ho retained Difference in mean Fe/Ca among shell hue classes? F-statistic 57 35 9.8 9.9 South Dakota only: 15.4 12.1 F = 0.42 F = 0.674 F = 2.044 F = 2.321 Ho retained Ho retained Difference in mean K/Ca among shell hue classes? F-statistic 57 35 1.89 1.24 South Dakota only: 3.33 2.59 F = 0.977 F = 8.25 F = 2.044 F = 2.321 Ho retained Ho rejected Difference in mean Mg/Ca among shell hue classes? F-statistic 57 35 14.5 10.3 South Dakota only: 21.9 10.0 F = 3.21 F = 7.78 F = 2.044 F = 2.321 Ho rejected Ho rejected Difference in mean Mn/Ca among shell hue classes? F-statistic 55 34 6.8 4.4 South Dakota only: 10.3 5.9 F = 1.3 F = 6.9 F = 2.054 F = 2.337 Ho retained Ho rejected Difference in mean Na/Ca among shell hue classes? F-statistic 57 35 15.9 9.2 South Dakota only: 25.2 8.9 F = 1.3 F = 1.6 F = 2.044 F = 2.321 Ho retained Ho retained Difference in mean Sr/Ca among shell hue classes? F-statistic 57 35 2.47 1.26 South Dakota only: 4.11 2.76 F = 1.59 F = 1.01 F = 2.044 F = 2.321 Ho retained Ho retained Mean Mg/Ca and Mn/Ca statistically differs w ith respect to shell color. For all other elements, the null hypothesis, that the mean values do not differ by color grouping, holds. All isotope ratios reported in Â‰ vs. PDB; all minor element ratios reported in mMol/Mol.
49 FIGURE 8 Â—Shell Color Stable Isotope Cross-Plot The opalescent shell clusters at isotopically heavy 18O and intermediate 13C relative to other shell. No clearly-defined pattern exists in relation to shell color and isotopes. FIGURE 9 Â—Shell Color Sr/Ca-Mg/Ca Cross-Plot
50 Samples from specimens with a light color, without yellow tones, have low Mg/Ca ratios.
51 TABLE 11 Â—Colors for Unaltered Shell, by Genus Placenticeras Hoploscaphite s Baculites Inoceramus Anomia Nymphalucin a Anisomyon Drepanocheilus 10YR3/6 o + 7.5Y9/4 + 10YR8/1 + 7.5YR8/2 + + + 10YR7/8 o o Opalescen t 10YR8/1 Opalescen t 7.5Y9/2 + Opalescen t N9 + + Opalescen t 5Y8/9 + 10YR7/11 7.5Y9/2 + + 5Y8/5 + N9 o 5Y8/9 Key: + = majority of samples fell within Sr/Ca and Mg/Ca ranges for Recent molluscs = majority samples fell outside of Sr/Ca and Mg/Ca ranges for Recent molluscs o = equal number of samples within and outside of ranges Based on the Mg/Ca and Sr/Ca ranges for Recent aragonitic (and, in the case of Anomia calcitic) shell, unaltered shell may come in several colors. The colors for unaltered shell depend in part on genus, with some genera, such as Inoceramus having many colors for unaltered shell, while others, like Placenticeras having fewer.
52 2.3.4 Cementation Suite: In the cementation suite, two questions pertaining to shell alteration were addressed. The first of these is whether the presence of cement, crystals precipitated within the phragmacone or growing upon the septa of ammonite shells, mirrors altered minor element concentrations and/or isotopic signatures. The second question is whether, for each sample site investigated, there is a difference between the minor element concentrations and/or isotopic signatures for cements, concretions, and shell. Significant differences in mean isotopic and/or minor element values among the cements, concretions, and shell could serve as indicators for sample contamination. For instance, if samples were taken from a Hoploscaphites for sclerochronology, and one showed minor element concentrations intermediate between unaltered shell samples and the concretion, concretion material was likely contaminating the sample and the isotopic data should therefore be disregarded. A pair of radar charts showing the concentrations of minor elements (Figure 10), in mMol/Mol calcium, shows that shell taken from cemented specimens may have higher concentrations of iron, magnesium, and sodium than shell taken from uncemented samples. The greatest Mg/Ca and Fe/Ca ratios are for the Game Ranch specimens, with Trask Ranch specimens having the greatest Na/Ca ratio and the second-highest Mg/Ca and Fe/Ca ratios. As Figure 11A shows, the average minor element compostion of the cement at the Game Ranch is highly enriched in iron and magnesium relative to the average shell from that location. The cement in the Trask Ranch, however, has a lower concentration of sodium than the average for the shell (Figure 11B). Kremmling cements show a relatively low concentration of all minor elements. Shell material for samples that were not in the Â“Cementation SuiteÂ” were selected
53 from shells that were not infilled with cement. These shell samples were added to the Â“Cementation SuiteÂ” data to statistically evaluate the differences between cemented and uncemented shell material. The only statistically significant difference with respect to minor element concentrations was the lower mean Mg/Ca concentration in uncemented specimens (Table 12). Other moderately strong relationships, using a one-tailed t test at 0.05 significance, were the lower Al/Ca ratio in uncemented specimens (t = 0.93 versus critical t = 1.663) and lower Na/Ca ratio in uncemented samples (t = 0.96 versus critical t = 1.656). Isotopically, there was a significant difference in the 13C ratio of shell with and without cementation, with lower average 13C values for the cemented shells. At t = 3.80 versus critical t = 1.656, this is the strongest relationship in the examination of cemented and uncemented shell. The oxygen isotope ratio produced the weakest statistical relationship and was, therefor e, significantly not affected by cementation. Figures 12, 13, and 14 display the Sr/Ca-Mg/Ca and 18O 13C cross-plots for the Kremmling, Game Ranch, and Trask Ranch sites, respectively. In the Kremmling, plot (Figure 12), the samples from cemented specimens seen directly to the right of the cement samples are the shells lowest in Sr/Ca and, thus, furthest from the limit for Recent aragonitic shell. These points have lower 18O and higher 13C than the uncemented samples. Their 13C is comparable with that for cement, whereas their 18O values are intermediate between the cement and samples from uncemented shells. For the Game Ranch site, isotopic data for the cement samples was not available due to low voltage on the mass spectrometer. Therefore, comparisons can only be made with respect to external crystallization. Shells with external recrystallization or cement had lower 13C values than the samples from uncemented shell and 18O values among the lowest for
54 shell (Figure 13). Two of three samples from shells bearing external recrystallization or cement had Sr/Ca-Mg/Ca profiles identical to shell without such precipitation; the third had a Sr/Ca-Mg/Ca profile similar to the concretions. The Trask Ranch data shows the samples from cemented and uncemented shell intermixed on the Sr/Ca-Mg/Ca plot (Figure 14). On the other hand, the isotope cross-plot clearly shows the samples from shell with cement intermediate between samples from uncemented shell and the subset of cement samples that are low in 13C. The samples from cemented shell appear to be dispersed along a line extending from the cluster of uncemented shell to the low 18O and 13C ratios of the cement. A linear fit of y = 0.892x Â– 4.286 links both cement and cemented shell with an r2 = 0.730. In order to properly compare samples from cemented shell, cement, and concretions, it must be determined if a significant difference exists between for each sampling location. A series of paired t-tests for dependent samples, reported in Tables 13-15, seeks to address this issue. All samples are from specimens that contained shell, concretion, and cement (or, in the case of the Game Ranch, externally precipitated cement or recrystallization). Al/Ca was omitted from the analysis of the Kremmling site because of scarce data. Partly because the standard deviations are relatively low, within the Kremmling data, the difference in the means of K/Ca and Mn/Ca ratios seen in Figure 11B are statistically significant. The smaller difference in means for Sr/Ca of the shell and cement samples implies that, while positioned completely to the right (higher Sr/Ca) of the cement in Figure 12, the shell samples are not statistically distinct. The 13C values for shell were significantly heavier than those for cement. When comparing shell to
55 concretion, the shell was significantly lower in Fe/Ca, K/Ca, Mg/Ca, and significantly higher in Na/Ca and Sr/Ca. Thus, on the Figure 12 Sr/Ca-Mg/Ca cross-plot, the concretions appear as a cluster with higher Mg/Ca and lower Sr/Ca than any of the shell samples. The remainder of the elements can be visually compared using Figure 11B; although this graph shows only the mean values, differences can be easily noted for all statistically significant minor element concentrations except the Na/Ca ratio. There was no significant difference between the isotopic signature of shell and concretion for Kremmling, as can be seen by the intermixed data points in Figure 12. The only statistically significant difference between and shell and concretion for the Game Ranch, South Dakota, data is lower 13C for the concretions. This can be seen in Figure 13 where the data points for the three concretion samples reside clearly below the shell data points. These points are isotopically heavier in 18O than the majority of the shell samples, so a fairly high t-score (t = 1.54 versus critical t = 2.132) results. Other strong relationships include lower Fe/Ca (t = -2.0), K/Ca (t = -1.80), Mg/Ca (t = -2.13), and Mn/Ca (t = -1.5) in shell, all with critical t = -2.13. The samples of external recrystallization or cement and interior cement compare with both concretions and shell by having much higher mean minor element concentrations, especially Fe/Ca, K/Ca, and Mg/Ca (Figure 11A).
56 Specimens recovered from Trask Ranch show two types of cements. For simplicity, these will be referred to as the Cement-1 and Cement-2 subsets. Cement-2 samples have lower Al/Ca and Mg/Ca, but higher Sr/Ca, than Cement-1 samples, and appear along the regression line with shell in the isotope cross-plot in Figure 14. A shift towards isotopically lighter 13C values is accompanied by a shift towards lighter 18O values. Cement-1 samples appear with concretion samples on the aforementioned graph. For these samples, a shift toward isotopically lighter 13C values is not correlated with any change in 18O. Cement-1 samples cannot be distinguished by appearance in hand sample, and use of thin sections would be advantageous for futher study. Using paired ttests for dependent samples, 0.05 level of significance, cemented shell shows significantly higher Na/Ca and Sr/Ca than Cement-1, as well as lighter 18O. This shell also has significantly lighter 13C. Though not statistically significant, the Mn/Ca values were lower for shell (t = -1.9 versus critical t = 2.132). When compared instead to Cement-2, shell has significantly lower Fe/Ca, Mg/Ca, and Mn/Ca, and higher Na/Ca and Sr/Ca. Other strong relationships include Al/Ca (t = 1.1 versus critical t = 1.860), which is higher in shell, and Mg/Ca (t = -1.72 versus critical t = -1.860), which is lower. Isotopically, as shown in Figure 16, shell is significantly heavier than Cement-2 with respect to carbon but shows no significant difference with respect to oxygen (t = 1.25 versus critical t = 1.895). Lastly, comparing shell from the cemented samples with their concretions, it has lighter 13C and heavier 18O (as visible in Figure 14); lower Al/Ca, Fe/Ca, K/Ca, Mg/Ca, Mn/Ca; and higher Na/Ca and Sr/Ca. The results for all of these comparisons, with the exception of Sr/Ca, are statistically significant. FIGURE 10 Â— Radar Charts for Minor Elements in Cemented and Uncemented Shell
57 Cemented shell appears to have higher possible concentrations of Fe, Mg, and Na. However, because n = 7 for the uncemented specimens in the Â“CementationÂ” suite, the dataset must be expanded into other suites to make more robust comparisons.
58 FIGURE 11Â— Minor Element Content of Â“Cementation SuiteÂ” Samples Figure 11A shows a very large enrichment in Fe/Ca, Mg/Ca, and Mn/Ca ratios for cements and external recrystallization or cement from the Game Ranch locality.
59 Figure 11B eliminates the Game Ranch interior cement and external recrystallization or cement samples, so the minor element ratios of the other cementation suite materials become apparent. There are higher Mg/Ca ratios, and sometimes Fe/Ca ratios, in concretions than in shell.
60 TABLE 12 Â—Summary of Statistical Tests on Cemented and Uncemented Shell The cemented shell shows lighter 13C and higher Mg/Ca ratios than uncemented shell. For all other tests, the null hypothesis of no significant difference in mean minor element concentrations or isotopic values between cemented and uncemented shell must be retained. Beyond the level of statistical significance, cemented shell shows lower Na/Ca and higher Al/Ca than uncemented shell. All isotope ratios reported in Â‰ versus PDB and all minor element ratios reported in mMol/Mol calcium.Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value(s) Critical Value (0.05 significance) Result Lighter mean 13C in cemented shells? one-tailed t test 100u, 30c u: -3.45 4.85 c: -7.065 3.410 t = 3.80 t = 1.656 Ho rejected Lighter mean 18O in cemented shells? one-tailed t test 100u, 30c u: -5.80 5.27 c: -5.62 5.00 t = -0.169 t = 1.656 Ho retained Lower mean Al/Ca in uncemented specimens? one-tailed t test 59u, 27c u: 5.4 5.9 c: 4.2 3.1 t = 0.93 t = -1.663 Ho retained Lower mean Fe/Ca in uncemented specimens? one-tailed t test 101u, 36c u: 8.8 15.5 c: 8.1 9.2 t = 0.2 t = -1.656 Ho retained Lower mean K/Ca in uncemented specimens? one-tailed t test 106u, 37c u: 1.76 1.82 c: 1.89 1.34 t = -0.41 t = -1.656 Ho retained Lower mean Mg/Ca in uncemented specimens? one-tailed t test 106u, 37c u: 11.5 12.4 c: 18.1 15.2 t = -2.63 t = -1.656 Ho rejected Lower mean Mn/Ca in uncemented specimens? one-tailed t test 101u, 37c u: 5.5 5.2 c: 6.0 5.2 t = -0.48 t = -1.656 Ho retained Higher mean Na/Ca in uncemented specimens? one-tailed t test 106u, 37c u: 16.9 9.9 c: 15.1 9.5 t = 0.96 t = 1.656 Ho retained Higher mean Sr/Ca in uncemented specimens? one-tailed t test 106u, 37c u: 3.0 2.8 c: 2.8 1.9 t = 0.36 t = 1.656 Ho retained
61 FIGURE 12 Â—Comparison of Cements, Concretions, and Shell Material for Kremmling
62 FIGURE 13 Â—Comparison of External Recrystallizations or Cements, Concretions, and Shell Material for Game Ranch
63 FIGURE 14 Â—Comparison of Cements, Concretions, and Shell Material for Trask Ranch
64 TABLE 13 Â—Statistical Tests for Kremmling Cements, Concretions, and Shell Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value(s) Critical Value (0.05 signif.) Result Heavier mean 13C in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: -5.45 2.03 co: -9.01 3.01 ce: -8.64 1.99 t(s-co) = -0.433 t(s-ce) = -3.11 t(s-co) = -1.895 t(s-ce) = -1.895 Ho retained Ho rejected Heavier mean 18O in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: -13.52 5.74 co: -12.49 1.28 ce: -13.00 3.83 t(s-co) = -0.909 t(s-ce) = -0.476 t(s-co) = -1.895 t(s-ce) = -1.895 Ho retained Ho retained Lower mean Fe/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 12.9 6.4 co: 19.4 10.6 ce: 11.5 5.1 t(s-co) = -2.8 t(s-ce) = -0.49 t(s-co) = -1.895 t(s-ce) = -1.895 Ho rejected Ho retained Lower mean K/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 0.67 0.12 co: 4.58 2.11 ce: 1.78 1.63 t(s-co) = -3.6 t(s-ce) = 2.0 t(s-co) = -1.895 t(s-ce) = -1.895 Ho rejected Ho rejected Lower mean Mg/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 10.4 5.3 co: 21.3 9.8 ce: 11.2 3.5 t(s-co) = -2.8 t(s-ce) = 0.48 t(s-co) = -1.895 t(s-ce) = -1.895 Ho rejected Ho retained Lower mean Mn/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 4.4 1.5 co: 11.7 3.2 ce: 11.20 4.57 t(s-co) = -0.33 t(s-ce) = 4.8 t(s-co) = -1.895 t(s-ce) = -1.895 Ho retained Ho rejected Higher mean Na/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 2.4 0.6 co: 4.24 1.52 ce: 5.47 4.35 t(s-co) = 4.4 t(s-ce) = 2.1 t(s-co) = 1.895 t(s-ce) = 1.895 Ho rejected Ho rejected Higher mean Sr/Ca in shell? paired t-tests (dependent samples) 8s, 8co, 8ce s: 0.4 0.1 co: 0.65 0.22 ce: 2.08 3.32 t(s-co) = 3.3 t(s-ce) = 1.4 t(s-co) = 1.895 t(s-ce) = 1.895 Ho rejected Ho retained At the Kremmling site, significant differences were found between concretions and shell, or cement and shell, for most minor elements. The only statistically significant difference in stable isotopes was heavier 13C in shell versus cement. The null hypothesis, that there is no significant difference between shell and concretion, and between shell and cement, was retained for all other isotopic comparisons and some minor element comparisons. All isotope ratios reported in Â‰ vs.PDB; all minor element ratios reported in mMol/Mol.
65 TABLE 14 Â—Statistical Tests for Game Ranch Concretions and Shell Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value(s) Critical Value (0.05 significance) Result Heavier mean 13C in shell? paired t-tests (dependent samples) 5s, 5co s: -1.91 1.67 co: -10.85 4.93 t(s-co) = -2.51 t(s-co) = -2.132 Ho rejected Heavier mean 18O in shell? paired t-tests (dependent samples) 5s, 5co s: -2.68 0.82 co: -1.56 0.25 t(s-co) = 1.54 t(s-co) = -2.132 Ho retained Lower mean Al/Ca in shell? paired t-tests (dependent samples) 2s, 2co s: 5.4 7.0 co: 21.9 21.4 t(s-co) = -1.8 t(s-co) = -6.314 Ho retained Lower mean Fe/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 8.1 13.3 co: 80. 72 t(s-co) = -2.0 t(s-co) = -2.132 Ho retained Lower mean K/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 2.21 2.31 co: 12.3 10.5 t(s-co) = -1.80 t(s-co) = -2.132 Ho retained Lower mean Mg/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 18.6 34.9 co: 51.9 16.9 t(s-co) = -2.13 t(s-co) = -2.132 Ho retained Lower mean Mn/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 3.5 5.2 co: 22.0 14.3 t(s-co) = -1.5 t(s-co) = -2.132 Ho retained Higher mean Na/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 17.4 4.4 co: 18.7 12.2 t(s-co) = -0.39 t(s-co) = 2.132 Ho retained Higher mean Sr/Ca in shell? paired t-tests (dependent samples) 5s, 5co s: 2.71 0.69 co: 2.09 0.63 t(s-co) = -0.89 t(s-co) = 2.132 Ho retained Among the Game Ranch samples, no significant differences were found between concretions and shell for minor elements. Several minor elements, however, approached statistical significance: Al/Ca, Fe/Ca, K/Ca, Mg/Ca, and Mn/Ca, all of which were higher in concretions. Heavier 13C occurred in shell versus concretions. The remainder of comparisons did not allow for the statistical rejection of the null hypothesis, no difference between isotopic values and minor element concentrations between shell material and concretions. All isotope ratios reported in Â‰ versus PDB and all minor element ratios reported in mMol/Mol calcium.
66 TABLE 15 Â—Statistical Tests for Trask Ranch Cements, Concretions, and Shell Alternate Hypothesis Type of Test N Means, std. deviations Calculated Value(s) Critical Value (0.05 signif.) Result Heavier mean 13C in shell? paired ttests (dep. samples) 14s, 14co, 5ce1, 8ce2 s: -7.96 3.15 co: -19.85 4.11 ce1: -12.12 3.96 ce2: -13.28 3.63 t(s-co) = 2.72 t(s-ce1) = 2.18 t(s-ce2) =1.25 t(s-co) = 1.771 t(s-ce1) = 2.132 t(s-ce2) = 1.895 Ho rejected Ho rejected Ho retained Heavier mean 18O in shell? paired ttests (dep. samples) 14s, 14co, 5ce1, 8ce2 s: -3.21 1.04 co: -2.59 1.53 ce1: -5.29 3.88 ce2: -4.63 3.48 t(s-co) = -1.85 t(s-ce1) = 1.41 t(s-ce2) = 0.33 t(s-co) = 1.771 t(s-ce1) = 2.132 t(s-ce2) = 1.895 Ho rejected Ho retained Ho retained Lower mean Al/Ca in shell? paired ttests (dep. samples) 14s, 14co, 5ce1, 9ce2 s: 4.0 3.3 co: 15.4 8.4 ce1: 5.6 8.4 ce2: 2.2 2.7 t(s-co) = -3.7 t(s-ce1) = 0.49 t(s-ce2) = 1.1 t(s-co) = -1.771 t(s-ce1) = -2.132 t(s-ce2) = -1.860 Ho rejected Ho retained Ho retained Lower mean Fe/Ca in shell? paired ttests (dep. samples) 15s, 15co, 5ce1, 9ce2) s: 4.4 3.5 co: 13.7 3.1 ce1: 7.3 4.9 ce2: 8.0 4.1 t(s-co) = -4.2 t(s-ce1) = -0.48 t(s-ce2) = -1.9 t(s-co) = -1.761 t(s-ce1) = -2.132 t(s-ce2) = -1.860 Ho rejected Ho retained Ho rejected Lower mean K/Ca in shell? paired ttests (dep. samples) 15s, 15co, 5ce1, 9ce2 s: 1.78 1.00 co: 4.98 1.58 ce1: 1.60 1.87 ce2: 1.55 0.81 t(s-co) = -4.0 t(s-ce1) = 0.50 t(s-ce2) = 0.33 t(s-co) = -1.761 t(s-ce1) = -2.132 t(s-ce2) = -1.860 Ho rejected Ho retained Ho retained Lower mean Mg/Ca in shell? paired ttests (dep. samples) 15s, 15co, 5ce1, 9ce2 s: 23.0 12.8 co: 79 24 ce1: 29.6 35.0 ce2: 32.0 23.7 t(s-co) =-4.73 t(s-ce1) = 0.05 t(s-ce2) = -1.72 t(s-co) = -1.761 t(s-ce1) = -2.132 t(s-ce2) = -1.860 Ho rejected Ho retained Ho retained Lower mean Mn/Ca in shell? paired ttests (dep. samples) 15s, 15co, 5ce1, 9ce2 s: 3.53 2.56 co: 11.2 7.2 ce1: 10.0 6.7 ce2: 6.9 4.1 t(s-co) = -3.1 t(s-ce1) = -1.9 t(s-ce2) = -4.4 t(s-co) = -1.761 t(s-ce1) = -2.132 t(s-ce2) = -1.860 Ho rejected Ho retained Ho rejected Higher mean Na/Ca in shell? paired ttests (dep. samples) 15s, 15co, 5ce1, 9ce2 s: 18.7 10.0 co: 9.4 3.9 ce1: 5.99 3.03 ce2: 11.25 13.81 t(s-co) = 3.5 t(s-ce1) = 2.55 t(s-ce2) = 2.22 t(s-co) = 1.761 t(s-ce1) = 2.132 t(s-ce2) = 1.860 Ho rejected Ho rejected Ho rejected Higher mean Sr/Ca in shell? paired ttests (dep. samples) 14s, 14co, 5ce1, 9ce2 s: 3.27 0.97 co: 0.89 0.09 ce1: 0.50 0.35 ce2: 0.59 0.39 t(s-co) = -0.60 t(s-ce1) = 20. t(s-ce2) = 7.5 t(s-co) = 1.771 t(s-ce1) = 2.132 t(s-ce2) = 1.860 Ho retained Ho rejected Ho rejected Statistically significant differences for the Trask Ranch site include Sr/Ca for the shell versus cements, 13C and 18O for the shell versus concretions, and Na/Ca for both. Most other comparisons resulted in the retention of the null hypothesis, no significant difference in the mean isotopic value or minor element concentration between shell and concretion or shell and cement. All isotope ratios reported in Â‰ versus PDB and all minor element ratios reported in mMol/Mol calcium.
67 2.4 Discussion 2.4.1 Review of Sample Suites : In the Â“Mode of PreservationÂ” suite, enrichment outliers in aluminum, iron, manganese, and strontium were present in the shell material found within the concretions. Furthermore, the concretions had statistically significant higher mean Fe/Ca and Mg/Ca, with a strong (but not statistically significant) relationship between mode of preservation and Mn/Ca ratio. Enrichment in Fe/Ca and Mn/Ca is a diagenetic signature indicative of interaction with meteoric waters (Veizer and Fritz, 1976) or cementation associated with methane seeps (Krause et al., 2003). Therefore, the ammonite specimens preserved in shale are less altered. Buchardt (1977) explains the superior preservation in shale as due to retention of the organic matrix in the low-permeability, chemically reducing environment. Another idea is that the formation of the concretion, itself a chemical phenomenon, sometimes significantly alters the shell that it precipitates around, partially dissolving the shell and reprecipitating the calcium carbonate as calcite within the shell microstructure. The precipitated calcite would have a minor element and isotopic signature between that of pure shell and that of the diagenetic fluid. Thus, taking samples only from the interior of concretions may minimize the effect of chemical weathering when concretions are exposed at the surface, but can do nothing to address early diagenetic alteration. Veizer and Fritz (1976) offer a manganese-based alteration equation to estimate the Â“degree of alterationÂ” from diagenesis: Degree of alteration (%) = (Mnshell Â– Mnequilibrium) x 100 (4) Mnenclosing rock carbonate Â– Mnequilibrium Using this equation, the average degree of alteration for the samples taken from shell
68 preserved in concretions was 33.3% 37.4%, whereas the average degree of alteration for shell preserved in shale was 5.6% 9.1%. These figures should be regarded as general estimates because the Â“Mode of PreservationÂ” suite did not contain samples of the concretions themselves, so an average Mn/Ca values for each locality, calculated from the Â“CementationÂ” suite data, was used. The effect of such alteration on isotopic signals is statistically significant for 18O, and nearly so for 13C. Therefore, shale should be the preferred source for shell material used in 18O paleotemperature and 13C productivity/diet calculations. A third idea, supported by further data in the Â“CementationÂ” suite, is that cements found in the concretions are formed by the same diagenetic fluids that cause shell alteration. There was no statistically significant difference in the mean concentrations of Na/Ca (~16 mMol/Mol), K/Ca (~0.8 mMol/Mol) or Sr/Ca (~3mMol/Mol) with respect to mode of preservation. The independence of concentrations of these elements from lithology suggests that shell from both concretions and shale could be used in paleosalinity calculations. In the Â“Shell Sampling LocationÂ” suite, ammonite septa and adjacent phragmacone were found to commonly display very different isotopic signatures. The 18O values of the septum-phragmacone pair s were significantly different at the 0.05 significance level, whereas the 13C values were not. With a sample size of only ten pairs available, clearly, a larger sample size is needed to resolve this issue. Mann (1992) found greater concentrations of Mg/Ca and Sr/Ca in Nautilus septa than in phragmacone. If true for the ammonite samples, this could indicate the influence of mineral-rich extrapallial fluid in shell precipitation. Alternately, higher Mg/Ca but lower Sr/Ca in the septa could indicate diagenetic alteration. The septa of ammonites are frequently
69 cemented to a greater degree than the phragmacone, and these cements, as Figures 12 and 14 illustrate, are lighter in 18O than the shell they precipitate upon. Differences in the minor element compostion of septa versus phragmacone shell, however, are minimal, so neither extrapallial fluid nor cementation is likely the cause of the isotopic disparity in this dataset. Paleosalinity calculations could therefore be performed on septa or phragmacone samples. Nearly all septa Â– in Placenticeras, Hoploscaphites and Baculites Â– have isotopically lighter 18O than the phragmacone samples. The depression of 18O along the septum is consistent with the highly negative 18O signature of Nautilus metabolic CO2, which contributes 0-10% of shell carbonate in Recent mollusks (Auclair et al., 2004). However, in a study of aquarium-raised Nautilus Landman et al. (1994) demonstrated that temperatures coincident with the temperature range of the aquarium could be derived from the shell 18O signature. Another suggestion is the time averaging inherent in the formation of a septum. A septum in wild, immature Nautilus may take from 23 to 75 days to precipitate (Cochran et al., 1981), while 0.2 mm of shell takes 17 to 30 days (Saunders, 1983). The onset of septal formation, coincident with the phragmacone samples in this study, could be at times of relatively lower temperature than the average temperature during the spans of time over which the septa were precipitated. Isotopically light 13C could also be a sign of metabolism, as ontogenetically young, small mollusks with a high metabolic rate accumulate more of the lighter isotope derived from food (Mitchell et al., 1994). Because 13C does not vary between septa and phragmcone, however, it may be possible to extract reasonable productivity/food source data from septa. In the Â“Shell ColorÂ” suite, the assertations of researchers (e.g., Forester et al.,
70 1977; Tsujita and Westermann, 1998) who advocate a preference for opalescent shell were supported slightly. Opalescent shell did tend to possess a lower Mg/Ca ratio, with magnesium being an indicator of the presence of secondary calcitic cement, while nonopalescent shell often was depleted in strontium. Strontium depletion will lead to erroneous paleosalinity values, so should be avoided in studies that include paleosalinity using the equation of Brand (1986). Opalescent shell also had isotopically heavier 18O, which might be less altered because both diagenetic cement and meteoric water have lighter 18O than shell material. However, neither of these findings is statistically significant, despite n = 55 (all locations) and n = 38 (South Dakota locations only). Only when Colorado data was removed did the differences in K/Ca and Mn/Ca ratios relate to color class. The only element to vary significantly with color, regardless of collection site, was magnesium (see Figure 9), which tends to be found at higher relative concentrations in yellow, orange, and brown shell material. In particular, the relationship between color class and 13C was weak, suggesting that any color of shell could be used in productivity/food source studies. In the Â“CementationÂ” suite, a comparison of cemented and uncemented shell material revealed a significant difference in only 13C. Cemented shell, therefore, may be used in paleosalinity and paleotemperature reconstructions, but not productivity/food source ones. At the Trask Ranch site, the isotopic signature of the cements which form a linear trend with the altered shell is consistant with second-order cements, having formed by waters of meteroric origin late after deposition (Wright, 1987). These findings conflict directly with the shell alteration model of Veizer and Fritz (1976), which uses the carbonate fraction of the rock (i.e., the concretion) as the composition of the diagenetic
71 fluid which determined manganese and/or iron enrichment. Therefore, for this locality, the shell alteration equation of Veizer and Fritz (1976) should be modified: Degree of alteration (%) = (Mnshell Â– Mnequilibrium) x 100 (5) Mnsecond order_cementÂ– Mnequilibrium Application of this modified equation, with Mnequilibrium = 15 ppm for seawater, to Trask Ranch shell data which have associated secondary cement and concretion values, yields a higher average percent altered (57%) for the cement calculation than for the concretion calculation (43%). Because this figure is an estimation of the percent secondary calcite present in a shell sample, it can be correlated with the actual percentage of calcite, as determined by X-ray diffraction, as part of a future study. The isotopic signature of the other cements at the Trask Ranch is consistent with first-order cements, formed by marine waters during early diagenesis (Brand, 1994). The first-order cements, which have the same 18O and 13C signatures as the concretions and a marine isotopic signature, do not appear to have altered shell associated with them. The matrix within the Trask Ranch concretions has slightly negative 18O values and very negative 13C values (-14 to -25Â‰), similar to those documented for ammonite-bearing concretions from the Late Cretaceous of eastern Siberia (Teys et al. 1978). The values are also similar to those of cements precipitated under conditions of methane oxidation and sulfate reduction for the Gulf of Mexico during the Pleistocene (Howard et al., 2005), and are similarly high in magnesium and iron. The concretions and cements of the Game Ranch locality are even higher in iron and magnesium, enough to classify them as veryhigh-magnesium or iron-calcites (Howard et al ., 2005). Again, this is characteristic of depositional environments where methane is being oxidized and sulfate reduced. More
72 shell material with cementation is also needed, as cementation was an uncommon phenomenon (n = 2 for n = 40 shell samples) in Game Ranch specimens. Exterior crystallization upon the shells had the same minor element and oxygen isotope signature as shell, and thus likely represented recrystallization of the shell rather than a secondary calcite precipitated from a late diagenetic fl uid. Concretions had isotopic signatures of 6Â‰ to -11Â‰ and -1Â‰ to -2Â‰ for 18O and 13C, respectively. The 18O values, heavier than those for Trask Ranch, were equivalent to those reported for a Turonian Western Interior Seaway dataset (Pagani and Arthur, 1998). Conceivably, the South Dakota concretions were formed from sediment and shell at the bottom of the Western Interior Seaway, perhaps initiated by the interface between an isotopically unusual bottom water and the slightly brackish but isotopically normal seawater above. Because of low oxygen, the presence of methane and sulfur, and rapid sedimentation vertebrate and crustacean predat ors did not disturb the organismsÂ’ remains. Instead, an anaerobic bacterial community, drawn to the organic matter accumulation, thrived. These bacteria produced methane and sulfur compounds. The isotopic signatures of the cements are clearly marine, so the effect from bacterial metabolism on the 18O value of the cement and concretions is likely negligible. The low carbon values of the concretions and infaunal organisms ( Drepanocheilus and Anisomyon ) are consistent with the accumulation of methane in the sediment pore spaces. A study of the sulfur present in shell, concretion, and cement, which is not possible with the ICP-OES system but could be performed by electron microprobe, could help establish the dynamics of such an ecosystem, as would observation of Recent anaerobic communities. There was, at least occasionaly, a large amount of sulfur in the Western Interior Seaway
73 because of large pyrite crystals and pyrite-replaced ammonites found in the Pierre Shale in Colorado. Regardless of the proportion of each bacterial type on the seafloor of the Western Interior Seaway, the products from the oxidation of methane and the reduction of sulfate are acidic, and could begin dissolving shell and reprecipitating it as cement to form the start of a concretion. Once the concretion begins growing, it could incorporate calcite from surrounding pore water, producing the characteristic isotopic values. However, this microbially favorable environment came to an end with the Western Interior Seaway, the shale containing concretions was exposed to meteoric water, and diagenetic fluids derived from it penetrated the concretions along planes of weakness, such as dewatering cracks and the fossils themselves. Under this hypothesis, the Â“septarianÂ” calcites which cross through the concretions should return signatures as Cement-2, influenced by meteoric water. Lastly, at Kremmling, Colorado, the concretions had a 18O signature similar to the Game Ranch concretion specimens, along with an isotopically light 13C signature (5Â‰ to -15Â‰) on the order of that in meteoric water. Because the isotopic signature of the Kremmling, Colorado, cements is identical to that of the concretions, the cement is likely first-order and thus precipitated from the same fluids that cemented the concretions. Shell material was similar to both concretions and cements in terms of isotopic composition, and appears to follow a J-shaped curve characteristic of alteration by meteoric water. Because Kremmling, Colorado, was a nearshore environment, continued regression during or slightly after the Baculites compressus/cuneatus biozones could have exposed the seafloor, even before the concretions fully lithified. This would explain the consistent, thorough alteration of the shell, especially the depletion in Sr/Ca
74 and Na/Ca, which are present in much smaller concentrations in freshwater than in saltwater. The shell nonetheless differed from concretions and cement in its minor element composition, with significantly lower Fe/Ca, K/Ca, and Mg/Ca ratios than cement, higher Na/Ca and Sr/Ca ratios than cement, and lower K/Ca and Mn/Ca, and higher Na/Ca ratios than concretions. In summary, the variety of isotopic signatures of concretions and cements across the Baculites compressus/cuneatus biozones suggest localized diagenetic environments. In terms of minor elements, secondorder cementation appears to have the strongest influence on shell light stable isotope chemistry, whereas concretion formation and first-order cements also influence the minor element concentration but appear to have less of an effect on isotopic signature of the shell material.
75 2.4.2 Utility of a Minor Element Alteration Indicator: With data from all four suites, an evaluation of the utility of a minor-element alteration indicator may be established. Appropriate minor elements to select should be those that, above or below a certain limit, correlate with unusually light isotopic values. The only minor element ratio that does so for both 18O and 13C is Mg/Ca. The Mg/Ca dataset has the added advantage of being more complete than the Fe/Ca and Mn/Ca datasets. For the 18O data, the Sr/Ca ratio also produces a fairly clear fit, among the minor elements that appear be linked to unusually light isotopes (Figure 15). Therefore, a Sr/Ca-Mg/Ca filter is proposed. The use of Sr/Ca was also proposed by Elorza and Garca-Garmilla (1996) in their study of aragonitic and calcite layers of Inoceramus specimens from Spain. For the Western Interi or Seaway, the data of Pagani and Arthur (1998) support the use of magnesium as an indicator of alteration. Their figures comparing minor element ratios with visually assessed shell preservation compared to Recent Nautilus show Mg/Ca as the best discriminator between well-preserved and poorly-preserved shell. In contrast, the fields for Fe/Ca and Mn/Ca content show significant proportions of the better-preserved shell outside the limits defined by Nautilus (Pagani and Arthur, 1998). Limits for these could be more conservatively based on the full spectrum of Recent aragonitic shellÂ—including habitats worldwide and representatives of Bivalvia, Gastropoda, and CephalopodaÂ—as given in Buchardt and Weiner (1981), instead of only Nautilus which lives, at least for part of its life, in a deepwater habitat that was nonexistent in the Western Interior Seaway. It is unlikely that Western Interior Seaway mollusks secreted shell with higher minor element concentrations than mollusks today. In life, mollusks discriminate against both Mg and
76 Sr in proportion with the concentration of these elements in seawater (Dodd, 1967). The chemistry of first-order marine cements in this study is unusual for the Late Cretaceous, which, based on oolitic limestones and first-order marine cements worldwide, generally had a high overall concentration of Ca in the water and low Mg/Ca ratios (Stanley and Hardie, 1998). Using halites, Trimofeff et al. (2006) demonstate that the Mg/Ca ratios in seawater were low in the Late Cretaceous compared to the present, though the authors calculate that the Early Cretaceous concentrations were even lower. Also, the geochemistry of waters formed under different oxygenation conditions would have influenced shell geochemistry. The Western Interior Seaway, at least in proximity to the sediment-water interface, was often dysoxic, as evidenced by the predominance of black shales. Therefore, the minor element concentrations of the concretions and cements may reflect unique geochemical conditions within the sediments at the bottom of the Western Interior Seaway. Because of this, an empi rical filter based on observations of anomalous 18O signatures, derived from Figure 15, is used. These values appear for Mg/Ca > 6.5 mMol/Mol, above the 2.5 mMol/Mol limit for Recent aragonitic molluscan shell material and Sr/Ca < 1.8 mMol/Mol, equivalent to the lower limit for Recent aragonitic molluscan shell (Buchardt and Weiner, 1981). Because higher Mg/Ca ratios than Recent shells are unlikely for the Late Cretaceous, the Mg/Ca acceptability level most likely represents a threshold above which the shell has interacted with mineral-rich diagenetic fluids enough to be isotopically altered and a most-conservative range for the possible minor-element ratios for Cretaceous shell material.
77 After applying the modified minor element filter described above to all data, when comparing the unfiltered isotopic data (Figure 16) with the filtered isotopic data (Figure 18A), several observations can be made. The first is that the filter eliminates the vast majority of data points, including the entire suite of Kremmling, samples. Data points for both 18O and 13C isotopically lighter than -6Â‰ are rejected by the filter, although the filter was created looking at values in the -10 to -15Â‰ range. Fields emerge for Baculites Inoceramus and Placenticeras with a Hoploscaphites point and four Nymphalucina points represented as well (two of these are outliers not included in the graph). All of the gastropods specimens from the genera Anisomyon and Drepanocheilus as well as the bivalve Anomia were excluded based on their minorelement ratios. However, further research is needed to determine if this loss is an effect of sample size (i.e., with a larger dataset of these fossils, less-altered specimens would be present) or whether the taxa do tend to contain higher concentrations of Mg/Ca and lower concentrations of Sr/Ca. If the latter is tr ue, the accuracy of isotopic signals from these genera needs to be determined. Figure 18B replicates the filtered isotopic data, with 90% confidence intervals surrounding the mean ( 18O, 13C) data point for each data subset. At the Game Ranch, the overlap of fields for Placenticeras and Baculites suggests that their habitats in life overlapped. Because of its shell morphology, Placenticeras had the most shallow implosion depth of any Western Interior Seaway ammonite, calculated by Tsujita and Westermann (1998) to be ~40 m. However, the total depth of the Western Interior Seaway during the Baculites compressus/cuneatus biozones (Harries, pers. comm., 2004), was likely shallower. Based on facies distribution patterns, Batt (1989) proposes
78 that Baculites were planktic but living at a slightly greater average depth than Placenticeras The position of Jeletskytes near the Placenticeras data points suggests a habitat in the upper water column, consistent the analysis of its mobility by Westerman (1996). The values for Inoceramus at the Game Ranch site are distinct, suggesting a different habitat from the ammonites. This benthic habitat must have had a different 18O signature, perhaps influenced by freshwater or by the unique chemical conditions at the bottom of a dysoxic sea. The separation of benthic epifaunal Inoceramus from the nektic ammonites is consistent with all other studies for the Western Interior Seaway reviewed in this paper. The overlap in ranges for the Trask Ranch site could indicate a less stratified water column at the time and location the organisms lived. Neither the relative nor the absolute timing, and neither the relative nor absolute depth, of the Trask Ranch and Game Ranch localities within the Baculites compressus biozone is known, and instability (with periodic seafloor dysoxia, which could also explain the abundant black shales) is likely in the Western Interior Seaway. Along with the salinity levels below normal-marine, the dysoxia explains the scarcity of echinoderms, corals, and rudist bivalves in the Western Interior Seaway deposits. Therefore, it is not unreasonable to conclude that the isotopic composition of the water could have varied on a short time scale. On the other hand, the overlap could be due to insufficient data or misapplication of minor-element filters. An important observation that should be made when comparing the 18O and 13C ranges for each genus (Figures 18 and 19, respectively) with statistical data taken for each genus at each location (Tables 16 and 17, respectively), is that the minor element filter is effective at identifyi ng localities that possess shell alteration. In selecting unaltered samples within each locality, the minor element filter discards many
79 samples that, nevertheless, yield reasonable 18O and 13C values. Of course, a value may be within the range of Â“reasonableÂ” values yet still not reliably record of the original paleoceanographic signals. The difference in mean isotopic composition between filtered and unfiltered data is not significant for any of the genus-location subsets at the 0.05 significance level, though the increase in 18O ratio of the Trask Ranch baculitids after the application of the filter points to a strong relationship, with t = -1.44 versus critical t = -1.69. The standard deviations for the data subsets do not decrease with the application of the filter. This suggests that despite the possibility of alteration as indicated by minorelement proxies, many specimens with Mg/Ca > 6 mMol/Mol or, to a lesser extent, Sr/Ca < 1.8 mMol/Mol, carry isotopic signatures no different than the Â“more pristineÂ” shell and that the isotopic signatures contained within shell material may be more robust than generally assumed. Why some fossil shell with increased Mg/Ca ratios and decreased Sr/Ca ratios relative to Recent aragonitic shell is isotopically identical to shell unaltered with respect to these chemicals is a topic that should be explored further. X-ray diffraction could deduce the percentage of calcite in the specimens, and any other minerals contributing to the minor element composition of the shell. Then, scanning electron microscopy of the specimens could reveal if the minerals are replacing aragonite or adhering to it, and if it is the latter, removal of the minerals could restore normal isotopic composition for samples (Cochran et al., 2005).
80 The values obtained in this study for agree well with prior research in the Western Interior Seaway, though the ranges are greater (Table 19). This study does document a larger 13C range than He et al. (2004) do for Inoceramus extending the bivalveÂ’s 13C signature towards heavier values, though the average remains an isotopically heavy 3.06 1.94Â‰. The Hoploscaphites value is heavier in 13C and lighter in 18O than their scaphite, though conclusions should not be overextended from a single data point. Differences may be due to taxonomic effect, as the other studies used other genera of scaphites, or to actual environmental variability. Lastly, the Placenticeras samples in this study, while isotopically light compared to contemporaneous ammonites, did not show the extremely light (-3.4Â‰ to -7.0Â‰) values documented by Tsujita and Westermann (1998), because their specimens were likely diagenetically altered. 2.4.3 Salinity and temperature calculations : Several authors (e.g., Rucker and Valentine, 1961; Dodd and Crisp, 1982; Rosenberg and Hughes, 1991) support a positive correlation between salinity and the concentration of sodium within molluscan shell. Brand (1986) found a positive relationship for a large dataset of bivalve and gastropods, both fossil and Recent, the empirically derived equation for which is: S = -5.769ln(A) + 28.380 (2) Salinity S is given in parts per thousand 0.5, and A is the ratio of ppm Sr / ppm Na, or the geometric mean of such ratios. Salinity has little to no correlation with Sr/Ca in molluscan shell (Purton et al., 1999), so Na is the measure of salinity, as advocated by Dodd (1967), and Sr/Ca corrects for taxonomic effects in minor element discrimination. Turekian and Armstrong (1960) show that the concentration of strontium in molluscan shell varies primarily by genus. This is likely because of intergeneric differences in
81 metabolic rate, which in turn determines the strontium concentrations of molluscs (Rosenberg and Hughes, 1991). Strontium concentrations are significantly higher in Recent cephalopods than in Recent bivalves and gastropods (Dodd, 1967), so the salinitySr/Na equation should not be applied directly to cephalopods, as it will overestimate the salinity. Using strontium and salinity data from Brand (1983) and Mann (1992), an adjustment factor of -1.5Â‰ was derived for the salinity of Nautilus The adjustment is approximate because it was derived from the average Sr/Ca values and environmental salinity for individuals of Nautilus found in prior research. This adjustment factor was then applied to the results of the equation on the ammonite specimens in the dataset. The resulting salinities ranged from 27.7 9.6Â‰ to 31.6 0.6Â‰ for the filtered dataset (Table 18). The lowest salinities were found in Placenticeras and Hoploscaphites and the highest were found in Inoceramus consistent with a seaway with denser, more saline water at the bottom. To calculate the mean 18O of the Western Interior Seaway seawater, the following equation, from Wright (1987), was used: S(WIS) = [1 Â– ( w(WIS)w(ocean)))/( f w(ocean))] x S(ocean) (3) Constants for 18O of the open ocean were w(ocean) = -1.22Â‰ PDB and S(ocean) = 34.3, values calculated from models of Earth without polar ice caps (Schmidt, 1997). The mean 18O (WIS) was calculated at ~-1.27Â‰, only slightly lighter than the oceanic value and comparable to the data of Schmidt (1997). Slingerland et al. (1996) advocate using freshwater cements as an indicator of freshwater 18O values, noting their general agreement with values from kaolinitic clay from the eastern shore of the Western Interior Seaway. A freshwater value of 18O = -12.72Â‰, equivalent to the freshwater first-order
82 cements/concretions at Kremmling, was used in calculations because this meteoric-waterderived freshwater was likely present shortly after the deposition of the fossils. It should be noted, however, that using the value of -20 to -25Â‰ advocated by Dettman and Lohman, produces 18O (WIS) values that are only 0.02Â‰ lower. Lastly, paleotemperature was calculated with Grossman and KuÂ’s (1986) equation for aragonitic shell: T(oC) = 21.8 Â– 4.69( c w). (5) All Inoceramus specimens were from the inner nacreous aragonitic layer, rather then the outer prismatic calcitic layer, so the calcite paleotemperature equation of Epstein et al. (1953) was not needed. For this equation, c= the 18O value of the shell and both this value and the w value are expressed relative to PDB (1986). Using Bettman and LohmanÂ’s freshwater signature, paleotemperatures are higher by 0.1 oC. The resulting values for Baculites agree with values given by He et al. (2005), Tsujita and Westermann (1998), Schmidt (1997), and Fatherree et al. (1998). The Game Ranch values are also equivalent to the Baculites values given by Zakharov et al. (2005) for Cretaceous material from the continental shelf of eastern Siberia, though these values are from an earlier time period, the Coniacian. The temperature equivalence implies that the genus Baculites lived in habitats of similar temperature across its geographic and stratigraphic range.
83 For Placenticeras a paleotemperature of 28.1 1.1 oC suggests that these ammonites lived in warm upper waters. This value is at the low end of the range Tsuijita and Westermann calculated, but, as stated previously, their isotopically light 18O values likely come from diagenetically altered material. The high (36 oC) paleotemperature for Hoploscaphites is slightly higher than values found for the scaphite Jeletskytes by Tsujita and Westermann (1998) and for Scaphites by Whittaker, Kyser, and Caldwell (1986). However, the value is at the high end of their range and is approximately at the boundary for cessation of shell precipitation for Recent aragonitic mollusks (Elliot et al., 2003). More unaltered specimens must be examined to determine if the mean shell precipitation is, in fact, closer to the average of 25oC found by Tsujita and Westermann (1998). The 13C value for the Hoploscaphites (Figure 20) is within the range of other ammonites, suggesting that the organism lived in a similar habitat. The Baculites specimens examined in this study yielded a paleotemperature of 20.9 4.9 oC for Game Ranch and 24.7 4.2 oC for Trask Ranch. However, as depicted in Figure 20, the isotopic ranges for Baculites specimens were quite wide. This could be a reflection of the temperature-induced natural variability in Baculites water-mass migration, short-term climate fluctuations, or an imperfect filter. It is possible that the differences in 18O between Tourtelot and RyeÂ’s (1969) Baculites data and Forester et al.Â’s (1977) Baculites data do not represent real temperature differences between the two locations, but are instead within the range of variability for Baculites from a single location. The 13C range for the Baculites specimens is comparable to both prior research and the 13C range for Placenticeras
84 While data for Placenticeras and Hoploscaphites are sparse, numerous studies provide comparative stable isotope and paleotemperature data for Inoceramus The range of values produced in this investigation, for both 18O and 13C, was comparable to prior research. For each of these isotopes, the range produced by this study is greater than any of the other ranges, but this could be an artifact of the greater amount of data examined. Tsujita and Westermann (1998) and Wright (1987) also obtain anomalously high paleotemperature values for Inoceramus The authors invoke the presence of highly saline bottom water to explain the values. An argument against this explanation, along with further discussion on the paleobiotic implications of these paleotemperatures, is presented in Chapter 3, Section 3.
85 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter A. 13C vs. Mg/Ca Above approximately 7 mMol/Mol, a greater number of unrealistic (10-20Â‰, versus PDB) 13C values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur at the same level. FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter (continued)
86 B. 18O vs. Fe/Ca Above approximately 7 mMol/Mol Fe/Ca, very negative 18O values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur above 9 mMol/Mol.
87 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter (continued) C. 18O vs. Mg/Ca Above approximately 6.5 mMol/Mol Mg/Ca, a greater number of unrealistic (10-20Â‰, versus PDB) 18O values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur above 12 mMol/Mol.
88 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter (continued) D. 18O vs. Mn/Ca Above approximately 11 mMol/Mol Mn/Ca, very negative 18O values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur above 12 mMol/Mol.
89 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter (continued) E. 18O vs. Na/Ca Below approximately 10 mMol/Mol Na/Ca, very negative 18O values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur below 9.5 mMol/Mol.
90 FIGURE 15 Â—Empirical Derivation of the Sr/Ca-Mg/Ca Filter (continued) F. 18O vs. Sr/Ca Below approximately 1.8 mMol/Mol Fe/Ca, very negative 18O values emerge for the Kremmling dataset. Isotopic outliers for Trask Ranch occur below 1.2 mMol/Mol.
91 FIGURE 16 Â—Stable Isotope Cross Plot for All Shell Samples The unfiltered graph for the stable isotope data shows two clear clusters defined by their oxygen isotope ratios. There is also a high degree of variability in samples of the same genus with regards to carbon isotopes.
92 FIGURE 17 Â—Isotope Cross-Plot For All Shell Samples, Filtered by Mg/Ca and Sr/Ca The stable isotope cross-plot of filtered data shows better-defined fields for each genus. The positioning of the fields relative to each other is consistent with prior research. The ammonites Baculites (green) and Placenticeras (blue) show a greater variability in oxygen isotopes, whereas the bivalve Inoceramus (red) shows more variation in carbon isotopes.
93 FIGURE 17 Â—Isotope Cross-Plot For All Shell Samples, Filtered by Mg/Ca and Sr/Ca, With 90% Confidence Intervals In this version of the isotope cross-plot for the filtered data, 90% confidence intervals are drawn from the mean data points. The 90% confidence interval means that if other samples of Western Interior Seaway fossils were taken from the sampling locations, the probability is 90% that they would fall within the confidence interval with the true population mean.
94 FIGURE 18 Â—Oxygen Isotope Range Chart Elimination of the data points with Mg/Ca a nd Sr/Ca outside of the limits of the minor element filter decreases the range of the 18O values for each genus such that all points fall between 1Â‰ and -6Â‰. However, it also eliminates less common genera such as Drepanocheilus and Anisomyon from the dataset.
95 TABLE 16 Â—Statistics Comparing 18O of Pre-filter and Post-filter Datasets Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value Critical Value (0.05 signif.) Result Lighter 18O for Game Ranch Baculites after filter? one-tailed t-test (ind.) 11u, 7f u: -1.21 0.84 f: -1.07 1.05 t = -0.34 t = -1.75 Ho retained Lighter 18O for Kremmling Baculites after filter? one-tailed t-test (ind.) 12u, 0f u: 11.56 5.75 N/A N/A N/A N/A Lighter 18O for Trask Ranch Baculites after filter? one-tailed t-test (ind.) 32u, 9f u: -2.44 1.14 f: -1.79 0.90 t = -1.44 t = -1.69 Ho retained Lighter 18O for Game Ranch Hoploscaphites after filter? one-tailed t-test (ind.) 1u, 0f u: -4.51 f: N/A N/A N/A N/A Lighter 18O for Kremmling Hoploscaphites after filter? one-tailed t-test (ind.) 7u, 0f u: -8.33 3.37 f: N/A N/A N/A N/A Lighter 18O for Trask Ranch Hoploscaphites after filter? one-tailed t-test (ind.) 13u, 1f u: -3.79 1.01 f: -4.41 N/A N/A N/A Lighter 18O for Game Ranch Placenticeras after filter? one-tailed t-test (ind.) 11u, 8f u: -3.17 0.90 f: -3.05 1.03 t = -0.29 t = -1.74 Ho retained Lighter 18O for Kremmling Placenticeras after filter? one-tailed t-test (ind.) 10u, 0f u: -15.23 1.42 f: N/A N/A N/A N/A Lighter 18O for Game Ranch Inoceramus after filter? one-tailed t-test (ind.) 9u, 7f u: -4.20 0.67 f: -4.27 0.68 t = 0.48 t = -1.76 Ho retained Lighter 18O for Kremmling Inoceramus after filter? one-tailed t-test (ind.) 3u, 0f u: -12.21 2.96 f: N/A N/A N/A N/A Lighter 18O for Trask Ranch Inoceramus after filter? one-tailed t-test (ind.) 6u, 6f u: -3.36 1.07 f: -3.36 1.07 N/A N/A N/A Lighter 18O for Game Ranch Anomia after filter? one-tailed t-test (ind.) 2u, 0f u: -2.99 1.25 f: N/A N/A N/A N/A Lighter 18O for Kremmling Anomia after filter? one-tailed t-test (ind.) 2u, 0f u: -4.63 1.01 f: N/A N/A N/A N/A Lighter 18O for Game Ranch Nymphalucina after filter? one-tailed t-test (ind.) 4u, 4f u: 0.25 0.19 f: 0.25 0.19 N/A N/A N/A Lighter 18O for Trask Ranch Nymphalucina after filter? one-tailed t-test (ind.) 2u, 0f u: -5.50 5.05 f: N/A N/A N/A N/A Lighter 18O for Trask Ranch Drepanocheilus after filter? one-tailed t-test (ind.) 3u, 0f u: -4.62 2.00 f: N/A N/A N/A N/A Lighter 18O for Trask Ranch Anisomyon after filter? one-tailed t-test (ind.) 2u, 0f u: -6.56 0.03 f: N/A N/A N/A N/A
96 FIGURE 19 Â—Carbon Isotope Range Chart The minor element filter likewise eliminates light 13C values from the dataset. Ammonites are then distributed between 2Â‰ and -5Â‰, and bivalves 6Â‰ to -1Â‰, except for an apparent outlier in Nymphalucina
97 TABLE 17 Â—Statistics Comparing 13C of Pre-filter and Post-filter Datasets Alternate Hypothesis Type of Test N Means, standard deviations Calculated Value Critical Value (0.05 signif.) Result Lighter 13C for Game Ramch Baculites after filter? one-tailed t-test (ind.) 11u, 7f u: -0.71 0.94 f: -0.51 1.07 t = -0.43 t = -1.75 Ho retained Lighter 13C for Kremmling Baculites after filter? one-tailed t-test (ind.) 12u, of u: -8.13 1.50 N/A N/A N/A N/A Lighter 13C for Trask Ranch Baculites after filter? one-tailed t-test (ind.) 32u, 9f u: -5.41 3.37 f: -2.67 1.30 t = -0.78 t = -1.69 Ho retained Lighter 13C for Game Ranch Hoploscaphites after filter? one-tailed t-test (ind.) 1u, 0f u: 0.544 f: N/A N/A N/A N/A Lighter 18O for Kremmling Hoploscaphites after filter? one-tailed t-test (ind.) 7u, 0f u: -13.59 1.23 f: N/A N/A N/A N/A Lighter 13C for Trask Ranch Hoploscaphites after filter? one-tailed t-test (ind.) 13u, 1f u: -6.13 2.97 f: -1.10 N/A N/A N/A Lighter 13C for Game Ranch Placenticeras after filter? one-tailed t-test (ind.) 11u, 8f u: -2.81 0.93 f: -2.31 0.93 t = -0.83 t = -1.74 Ho retained Lighter 13C for Kremmling Placenticeras after filter? one-tailed t-test (ind.) 10u, 0f u: -6.593 1.564 f: N/A N/A N/A N/A Lighter 13C for Game Ranch Inoceramus after filter? one-tailed t-test (ind.) 9u, 7f u: 4.52 1.20 f: 4.29 1.27 t = 0.30 t = -1.76 Ho retained Lighter 13C for Kremmling Inoceramus after filter? one-tailed t-test (ind.) 3u, 0f u: -5.16 3.72 f: N/A N/A N/A N/A Lighter 13C for Trask Ranch Inoceramus after filter? one-tailed t-test (ind.) 6u, 6f u: 1.63 1.60 f: 1.63 1.60 N/A N/A N/A Lighter 13C for Game Ranch Anomia after filter? one-tailed t-test (ind.) 2u, 0f u: -2.02 1.56 f: N/A N/A N/A N/A Lighter 13C for Kremmling Anomia after filter? one-tailed t-test (ind.) 2u, 0f u: 1.31 0.76 f: N/A N/A N/A N/A Lighter 13C for Game Ranch Nymphalucina after filter? one-tailed t-test (ind.) 4u, 4f u: -4.11 9.42 f: N/A N/A N/A N/A Lighter 13C for Trask Ranch Nymphalucina after filter? one-tailed t-test (ind.) 2u, 0f u: -7.84 7.30 f: N/A N/A N/A N/A Lighter 13C for Trask Ranch Drepanocheilus after filter? one-tailed t-test (ind.) 3u, 0f u: -11.33 6.69 f: N/A N/A N/A N/A Lighter 13C for Trask Ranch Anisomyon after filter? one-tailed t-test (ind.) 2u, 0f u: -9.67 1.54 f: N/A N/A N/A N/A
98 TABLE 18 Â—Paleoenvironmental Parameters Derived from Filtered Data Mean 18O (shell), Â‰, Standard Deviation Mean Salinity, Â‰, Standard Deviation Mean 18O(WIS), Â‰, Standard Deviation Mean Paleotemperature, oC, Standard Deviation Game Ranch Baculites -1.07 1.0430.6 0.8-1.26 0.08 20.9 4.9 Trask Ranch Baculites -1.79 0.9129.9 2.0-1.26 0.02 24.8 4.2 Game Ranch Placenticeras -3.05 1.0328.1 1.1-1.28 0.01 30.1 4.9 Trask Ranch Hoploscaphites -4.41 (n = 1)27.3 (n = 1)-1.29 (n = 1) 36.5 (n = 1) Game Ranch Inoceramus -4.27 0.6831.1 1.9-1.25 0.02 36.1 3.2 Trask Ranch Inoceramus -3.36 1.0727.7 9.6-1.28 0.09 31.5 4.9 Game Ranch Nymphalucina 0.25 0.1931.7 0.6-1.25 0.01 14.8 1.2 The salinity, calculated using the strontium and sodium concentrations in the shell, was used to determine the mean 18O for the Western Interior Seaway. Taking 18O of freshwater to be equal to the mean 18O of Kremmling, Colorado concretions (because the western coastline was the likely source of more freshwater input to the seaway), the mean paleotemperature for each organism at each location was calculated. The data support the notion of lower than normal salinity in the upper-intermediate waters of the seaway and verify the unrealistically high paleotemperatures for benthic epifaunal bivalves.
99 FIGURE 20Â— Stable Isotope Ranges for Genera in this Study and Prior Research Results of this study showed comparable light stable isotope signatures with data found by previous studies in the Western Interior Seaway.
100 CHAPTER 3. SCLEROCHRONOLOGY 3.1 Previous Investigations of Molluscan Sclerochronology 3.1.1 Advantages of Molluscan Sclerochronology: Sclerochronology is the study of changes in the chemical composition of a shell over an organismÂ’s lifespan, taken along the growth axis. Chemical composition in this context can be stable isotopic or minor element data. Molluscs are ideal for sclerochronology be cause they grow accretionally, and most have well-defined growth bands that may be used to evaluate the relative age of different parts of the shell and orient the growth axis. For most mollusks, growth is non-destructive; in order to precipitate additional shell, a mollusk does not need to dissolve previously precipitated shell material. Therefore, all shell deposition from embryonic to gerontic stages is generally recorded in a single shell. The record of a single shell contains chemical information with respect to time on the order of months, years, or decades, a resolution generally not available by comparing specimens from different stratigraphic horizons or even within a stratigraphic horizon, which is necessarily time-averaged due to depositional processes. Although mollusks strongly discriminate with respect to elements such as magnesium and strontium found in seawater, they precipitate oxygen and carbon at isotopic ratios close to equilibrium with seawater (e.g., Dodd, 1967; Landman et al., 1994; Elliot et al., 2003). 3.1.2 Cessation of Growth: One limitation in evaluating paleotemperature using molluscan shell is that mollusks do not grow throughout the year (Ivany et al., 2003), although this may have been less of a factor during more equable greenhouse conditions.
101 Bivalves cease deposting shell when the temperature becomes too hot or too cold, or when the mollusk is spawning. These cessations distort the temperature curve derived from 18O. Fatherree (1995) documented this effect for winter cessation of growth for the Western Interior Seaway bivalve Arctica ovata, so it is possible even in the more equable climate of the Cretaceous. Whether this cessation is related to temperature or spawning is unknown, as the spawning cycle of the bivalve is unknown. In their study of Recent Mercenaria mercenaria Elliot et al. (2003) note that the bivalve, which spawns in March-June, grew more slowly in summer months than in winter, and grew more slowly overall in inlets with highly variable salinity. Sepia showed slowed growth when it was in periods of starvation (Bettencourt and Guerra, 1999). 3.1.3 Metabolism: Another challenge of molluscan sclerochronology is the Â“vital effect,Â” or metabolic signature. All mollusks display a kinetic effect with regards to minor elements, precipitating shell with less strontium and magnesium than seawater (Dodd, 1982). However, the amount of discrimi nation differs based on shell mineralogy; calcitic bivalves discriminate less against magnesium and more against strontium as compared to aragonitic bivalves (Dodd, 1967). Sodium discrimination also varies, with higher sodium concentrations found in cephalopods than in bivalves or gastropods (Dodd, 1967; Brand, 1983). Mollusks, while not discriminating against heavy isotopes in the manner that plants and bacteria do, display a metabolic effect with regards to oxygen and carbon isotopes. When a correlation between 18O and 13C is positive, it may be due to alteration or to metabolism. At higher metabolic rates, mollusks incorporate more elements contained in their food supply, rather than from seawater, into their shells (e.g., Barrerra et al., 1990; Ivany et al., 2003). Because all molluscan food sources are
102 isotopically lighter than seawater, the net effect is an isotopically lighter shell. Barrerra et al. (1990) found positive correlations between stable isotopes in the bivalve Admussium colbecki along the metabolically active, fastest-growing parts of the shell. The positive correlations for the early ontogeny of Eutrephoceras (Landman et al., 1983), Baculites (Fatherree et al., 1998), and the bivalve Cucullaea (Dutton et al., 2002) may represent a rapid initial growth rate. When studying another Recent bivalve, Mercenaria mercenaria Elliot et al (2003) found direct relationships between stable isotopes for specimens living in ideal habitats but inverse relationships between the variables where the environment was less conducive to growth and had a shorter summer growth period. 3.1.4 Analogs for Mollusks of Western Interior Seaway: Ammonites and inoceramids are extinct organisms with no close relatives, so the interpretation of their sclerochronology must rely on more distantly related analogs. The most common analog used for ammonites is the shelled cephalopod Nautilus of which there are four extant species (Mann, 1992). The cuttlefish Sepia which may be phylogenetically more closely related to ammonites than Nautilus has also been examined. Sepia 13C values increase as individuals mature and migrate from in lets with high freshwater input (and highly negative 13C of dissolved inorganic carbon) into the open ocean, though the change in 13C ratio may also reflect changing diet. Temperature values obtained by oxygenisotope paleothermometry fall between 14 oC and 22 oC and slightly overestimate the actual temperature of the inlets in which the Sepia lived, as well as the temperature of aquaria where Sepia were experimentally raised (Bettencourt and Guerra, 1999). Though the authors explain this mismatch as evidence of a slight vital effect, it could also be the result of the temperature-based shell secretion rates they observed for the organism. As
103 Ivany et al. (2003) established for the surf clam Spisula if more shell is deposited in warmer temperatures, the oxygen-isotope paleothermometry values will be biased towards the warmer seasons (2003). However, Nautilus belauensis individuals raised in an aquarium at 15-24 oC did not show any evidence of temperature-determined growth cessation, or any variation in the oxygen isotopi c signature that could not be explained by equilibrium precipitation of aragonite (Landm an et al., 1994). This finding suggests that the shift in 18O documented for wild Nautilus and potentially other shelled cephalopods after hatching is temperature-dependent rather than physiological. Certain bivalves, such as Anomia may be compared directly with Recent counterparts, with the caveat that over 73 million years, taxonomic uniformitarianism may not hold for such factors as salinity tolerances and habitat preferences. There are no close relatives to Inoceramus so Wright (1987) applied paleotemperature and paleosalinity equations derived for Mytilus on the basis of benthic habitat and similar shell mineralogies. However, with generic-level controls exerting a substantial influence on Mg/Ca and Sr/Ca ratios in Recent bivalves (Turekian and Armstrong, 1960), the comparison could be flawed. 3.2 Methods 3.2.1 Sampling Locations: Specimens for sclerochronology were selected based on the results of the shell alteration investigation. A suite of specimens that possessed both thick, contiguous shell and Sr/Ca and Mg/Ca ratios similar to Recent aragonitic (or, in the case of Anomia calcitic) mollusks was assembled. The samples included seven Baculites of differing diameters, two Eutrephoceras two Hoploscaphites three Inoceramus one Anomia and one Nymphalucina
104 These shells were sampled using a Dremel variable-speed drill along ontogenetic growth at 2.5 mm intervals starting from the ontogenetically oldest part of shell available. Samples were taken from the part of the shell where growth lines were spaced the furthest apart to maximize the precision. The surface layer of shell was initially excavated into using a flat-bottomed, 3Â–mm bit to clear away surface contaminants and avoid the light isotopic ratios seen by Mitchell et al. (1994). The internal shell layers were sampled with a 1-mm bit at a consistent depth that, whenever possible, did not penetrate to the inner layer of the shell, where isotopes could be enriched by metabolic CO2 as noted by Auclair et al. (2004) for Nautilus When shell material was limited, as in the Eutrephoceras every other sample was taken for ICP-OES analysis and the even increments (0 mm, 5 mm, etc.) reserved for mass spectrometer analysis. In other cases, each odd sample (2.5 mm, 7.5 mm, etc.) was collected such that it could be run for both analyses. For each shell, samples were also taken 2.5 or 5.0 mm apart along specific growth lines, to serve as comparision to the range of values in the ontogenetic sequence. 3.2.2 Treatment and Analysis of Samples : Treatment and analysis of samples followed the same ICP-OES and mass spectrometer protocol as discussed in Chapter 2. The ICP-OES samples (see Appendix C) were run first so that their data could be used as a minor-element filter for the mass spectrometer. From these candidates, three specimens (depicted in Figure 20) were selected for isotopic analysis (see Appendix D). 3.2.3 Data Processing: Minor element data, reported in ppm, was once again translated into mMol/Mol Ca. These data were then subjected to the Sr/Ca-Mg/Ca minor element filter as discussed in Chapter 2. Sclerochronology candidates which fulfilled the
105 requirements of the minor element filter for at least 80% of their data points were then examined in terms of other minor element ratios that had been linked to altered 18O values, namely Fe/Ca, Mn/Ca, Sr/Ca, and Na/Ca. The three candidates with the minor element ratios least likely to be diagenetically altered were selected for isotopic analysis. As in the shell alteration investigation, paleoceanographic parameters were calculated from the 18O and 13C ratios, as well as the concentrations of strontium and sodium. Paleosalinity was calculated using the equation of Brand (1986): S = -5.769ln(A) + 28.380 (2) Salinity S is given in parts per thousand 0.5, and A is the ratio of ppm Sr / ppm Na, or the geometric mean of such ratios. The salinity values for each point were then substituted into an equation (Wright, 1987) for the 18O of the Western Interior Seaway water mass in which the organisms were living: S(WIS) = [1 Â– ( w(WIS)w(ocean)))/( f w(ocean))] x S(ocean) (3) Models of the Earth without polar ice caps provided the constants for 18O of the open ocean, w(ocean) = -1.22Â‰ PDB, and salinity of the open ocean, S(ocean) = 34.3Â‰ (Schmidt, 1997). Lastly, the w(WIS) value and 18O for each sample of shell material were substituted into Grossman and KuÂ’s molluscan aragonite paleothermometry equation: T = 21.8 4.69( 18Oarag 18Ow) (1) where 18Oarag is the isotopic signature of the shell material.
106 FIGURE 21 Â—Specimens Used in Sclerochronology A. Inoceramus Specimen I2 B. Baculites Specimen B7
107 FIGURE 21 Â—Specimens Used in Sclerochronology (Continued) Based on minor element concentrations, three specimens were selected to be examined with the mass spectrometer. Inoceramus specimen I2 was from the Game Rach locality, and was infilled with, but not enclosed by, concretionary material. Baculites specimen B7 was also from the Game Ranch locality, preserved directly in the shale. Eutrephoceras E2 was recovered from a concretion at the Trask Ranch locality.
108 3.3 Results 3.3.1 Inoceramus: Of the bivalve specimens, I2 was selected because of its relatively uniform minor element concentrations (Figure 22). The Nymphalucina specimen N1 was excluded because of peaks in Fe/Ca, the Inoceramus specimen I3 was not considered because of peaks in Mg/Ca, Mn/Ca, and Fe/Ca, and the Anomia specimen A1 and Inoceramus specimen I1 were dismissed because of numerous peaks in multiple minor elements. The mean minor element ratios in the I2 shell material, in mMol/Mol, were Fe/Ca = 0.86 1.49, K/Ca = 0.522 0.142, Mg/Ca = 1.12 0.42, Mn/Ca = 0.049 0.046, Na/Ca = 19.8 0.7, and Sr/Ca = 2.25 0.93. Therefore, the specimen is considered favorable under the Sr/Ca-Mg/Ca minor element filter, and all other possible minor-element filters examined in Chapter 2. The Al/Ca dataset was incomplete so is omitted in this analysis. No general trends in minor element ratios were observed through ontogeny. Noticable deviations in minor element ratios occurred only at the last data point, taken closest to the aperature of the shell. At this point, the Mg/Ca and Fe/Ca ratios increased. The increases, however, do not correspond with changes in isotopic composition (Figure 23). In general, the 18O and 13C ratios for the Inoceramus specimen are inversely related. A plot of these isotopes against each other (Figure 24), however, does not produce a significant correlation. The exception to this pattern occurs in shell samples taken from 0-7.5 mm in distance from the umbo. Ontogenetically, these are the earliest shell samples. In addition, the point at 12.5 mm, displays minima for both isotopic ratios. For the four 18O maxima that occur after 7.5 mm, labeled in Figure n+1, three are coincident with 13C minima, while the other preceded the 13C minima by one sampling
109 interval. The 18O minima also broadly correlate with salinity minima calculated from BrandÂ’s Sr/Na equation (1986). For the Inoceramus the 18O represented in the data ranges from -2.21Â‰ to -7.02Â‰, and salinity from 32.2Â‰ to 33.6Â‰, corresponding to paleotemperatures of 26.4 oC to a very unlikely paleotemperature of 48.9 oC. The paleosalinity curve approximately parallels the 18O curve, with the exceptions of the ontogenetically earliest sample and the two 18O maxima (temperature minima). These temperature minima are spaced ~40 mm apart and are of approximately the same amplitude. The ontogenetically earlier minimum is ~7 oC warmer than the ontogenetically later minimum, while the ontogenetically earliest data point is ~8 oC warmer than the ontogenetically latest data point. However, the ranges in temperature and salinity for the Inoceramus do not necessarily represent the total range possible for the organismÂ’s lifespan. The accretion of the inner nacreous layer of aragonite is such that a sample taken in a given location will contain not only the paleoceanographic signature of the conditions during formation, but, below that, the signatures of shell formed later. Therefore, the sclerochronologic record of the Inoceramus is greatly timeaveraged. Depending on the relative thickness of the layers secreted along the inside of the shell, the salinity and temperature profiles (Figure 25) that are produced may or may not be proportional to time. Comparing the ontogenetic variability in 18O and 13C (n = 25) to the variability present in a single growth line at distance = 20 mm (n = 9), a lower standard deviation is present for the growth line than for the ontogenetic sequence. The standard deviation of the ontogenetic sequence is 0.97Â‰ for 18O and 0.67Â‰ for 13C, whereas these values are 0.68Â‰ for 18O and 0.49Â‰ for 13C for the growth line. Based on one-tailed t-tests
110 with a 0.05 level of significance, there is no statistically significant difference between the mean 18O value of -5.46 0.97Â‰ for the ontogenetic sequence and -5.39 0.68Â‰ for the growth line, or between the mean 13C value of 5.48 0.67Â‰ for the ontogenetic sequence and 5.62 0.49Â‰ for the growth line. The sample taken from the I2 concretion produced no data due to mass spectrometer error.
111 FIGURE 22 Â—Minor Element Ratios for Sclerochronology: Bivalves The inoceramid bivalve I2 shows the most consistent, low Fe/Ca, Mg/Ca, and Mn/Ca values. With twelve values for the minor element analysis, representing six centimeters, it is also the longest record for the sclerochronology candidate bivalves. Therefore, this specimen was selected for isotopic analysis. N1 = Nymphalucina A1 = Anomia I1-I3 = Inoceramus
112 FIGURE 23 Â—Sclerochronology of Inoceramus Specimen I2
113 FIGURE 24 Â— 18O Versus 13C for Inoceramus Specimen I2 13C, Â‰ vs. PDB 18O, Â‰ vs. PDB Although most relative maxima in the 18O curve correspond to relative minima in the 13C curve, a statistically significant linear correlation cannot be fit to the data. The data points below 18O = 5.2Â‰ do not appear to fit any pattern; it is possible to see a slight negative trend to the clustered data of 18O values heavier than 5.2Â‰.
114 FIGURE 25 Â—Calculated Paleotemperature through Â“OntogenyÂ” for Inoceramus Specimen I2 Although the Â“ontogeneticÂ” sequence for the Inoceramus is time-averaged, a sine curve fits the temperature data reasonably well.
115 3.3.2. Baculites: Of the six Baculites specimens, B7 was selected because of its relatively uniform minor element concentrations (Figure 26), which satisfied all possible minor element filters. The mean minor element ratios in the shell, in mMol/Mol, were Fe/Ca = 0.389 0.218, K/Ca = 0.86 0.26, Mg/Ca = 1.31 0.91, Na/Ca = 21.4 3.4 (19.8 0.9 without outlier), and Sr/Ca = 2.72 0.29. The Al/Ca and Mn/Ca datasets were incomplete so are omitted in this analysis. No general trends in minor element ratios were observed over ontogeny. Noticable deviations in minor element ratios occurred at 12.5 mm from the ontogenetically youngest point on the specimen, where Mg/Ca increased from 1.14 to 3.04 mMol/Mol, and 17.5 mm, where the Na/Ca ratio changed from 19.9 to 28.2 mMol/Mol. In both cases, the sampling location directly following the deviation showed minor element ratios returning approximately to the predeviation value. As in the Inoceramus specimen, the increases in Na/Ca and Mg/Ca do not correspond with changes in isotopic composition (Figure 27). In general, the 18O and 13C ratios for the Baculites specimen are directly related (Figure 28). A plot of these isotopes agai nst each other (Figure 29) does not produce a statistically significant trendline. The sclerochronologic variations for the Baculites likewise show similar trends, albeit with vastly different magnitude fluctuations, between 18O and 13C data curves. For every 18O maximum, there is an equivalent 13C maximum at the same location, or one sampling location later in time/distance. Relative maxima occur at 5.0, 12.5, and 17.5 mm from the ontogenetically earliest sample. Relative minima occur at 0.0, 10.0, 15.0, and 25.0 mm. Through ontogeny, the amplitude of the 18O and 13C excursions decreases. There does not appear to be any relationship between the 18O and 13C maxima and the salinity data curve (Figure 30) derived from
116 BrandÂ’s Sr/Na equation (1986). For the Baculites 18O ranged from -0.97Â‰ to -1.84Â‰, and salinity from 31.7Â‰ to 35.5Â‰, corresponding to paleotemperatures of 20.9 oC to 22.6 oC. The highest salinity value corresponds to the Na/Ca peak, and if this point is disregarded as a statistical outlier, the maximum salinity is 32.4Â‰ and the minimum paleotemperature is unaffected. There is a possible general decrease in 18O over ontogeny as well as the aforementioned trend in the amplitude of minima and maxima. Comparing the ontogenetic variability in 18O and 13C (n = 11) to the variability present in a single growth line at distance = 15 mm (n = 8), a lower standard deviation is present for the ontogenetic sequence than for the growth line. The standard deviation of the ontogenetic sequence is 0.24Â‰ for 18O and 0.81Â‰ for 13C, whereas these values are 1.23Â‰ for 18O and 0.72Â‰ for 13C for the growth line. Based on one-tailed t-tests with a 0.05 level of significance, there is no statistically significant difference between the mean 18O value of -1.28 0.24Â‰ for the ontogenetic sequence and -1.65 0.72Â‰ for the growth line, or between the mean 13C value of -3.25 0.81Â‰ for the ontogenetic sequence and -3.62 0.42Â‰ for the growth line. The sample taken from the B7 concretion returned a 18O value of -2.10Â‰ and a 13C value of -23.65Â‰.
117 FIGURE 26 Â—Minor Elements Used for Sclerochronology: Baculites Among six Baculites specimens (B2-B7) screened, B7 had the most consistent K/Ca, Mg/Ca, Mn/Ca, and Sr/Ca values. Peaks in Mg/Ca and Na/Ca do exist at the middle of the ontogenetic sequence.
118 FIGURE 27 Â—Sclerochronology of Baculites Specimen B7 While the deviation in Na/Ca ratio seen at 17.5 mm from the ontogenetically earliest sample influenced the calculated salinity of Baculites specimen B7, it did not coincide with a change in 18O or 13C. There was also no associated change in 18O or 13C associated with the Mg/Ca peak at distance = 12.5 mm.
119 FIGURE 28 Â—Stable Isotope Sclerochronology of Baculites Specimen B7 In general, the 18O or 13C curves for Baculites specimen B7 parallel each other. The three labeled maxima in the 18O curve match with three maxima in the 13C curve, though the amplitude of the variations in the 13C curve is much greater.
120 FIGURE 29 Â— 18O Versus 13C for Baculites Specimen B7 13C, Â‰ vs. PDB 18O, Â‰ vs. PDB The 18O and 13C of Baculites specimen B7 do not produce a statistically significant linear fit. There does, however, appear to be a general trend of increasing 18O with increasing 13C.
121 FIGURE 30 Â—Calculated Paleotemperature and Paleosalinity for Baculites Specimen B7
122 3.3.3 Eutrephocera s: Of the Eutrephoceras specimens, E2 was selected because it offered the most expansive dataset. Minor element ratios for the two specimens were comparable. The E2 dataset included more samples taken from the inner whorls of the shell, including two samples from the neanoconch, the early developmental stage characterized in Eutrephoceras by cancellate ornamentation (Landman et al, 1983). E2 also had fewer mass spectrometer errors or underweight samples. While the minor element ratios vary more than in the Inoceramus or Baculites specimens, the Sr/Ca ratio is reasonable with respect to the filter limits. The Mg/Ca ratio peaks above 6.5 mMol/Mol at 12.5, 32.5, and 62.5 mm from the ontogenetically earliest point (Figure 31). All of these points are coincident with the appearance of cement upon the septa. The cement is highly enriched in Mg, with Mg/Ca values of 71.9 mMol/Mol and 32.7 mMol/Mol. Fe/Ca and Mn/Ca ratios, also higher in the cement than in the shell, peak at these locations as well. Na/Ca minima coincide with these maxima. The cement nearest to the protoconch coincides with a slight increase in both 18O and 13C, although this could be circumstantial. The 18O and 13C curves in Eutrephoceras specimen E2 appear to parallel each other (Figure 32), and when the stable isotopes are plotted against each other as in Figure 33, a positive, statistically significant linear fit emerges. This trendline has a strong r2 value of 0.673 and a p-value of 4.52 x 10-4. The isotopes share relative minima at 40, 55, 75, 85, 105, and 170 mm from the protoconch. The largest deviations are those at 55, 105, and 175, and may represent a periodic trend. There does not appear to be any trend in the amplitude of these minima, nor any overall trend in 18O and 13C. Another relationship which emerges from the sclerochronologic investigation of Eutrephoceras
123 specimen E2 is, as in Baculites specimen B7, a general positive correlation between 18O and salinity (Figure 34). This relationship is stronger for the interior portion of the shell. Clearly, the datapoints latest in ontogeny show anomalous 13C and Na/Ca. Comparing the ontogenetic variability in 18O and 13C (n = 28) to the variability present in a single growth line at distance = 125 mm (n = 8), a higher standard deviation is present for the ontogenetic sequence than for the growth line. The standard deviation of the ontogenetic sequence is 0.80 Â‰ for 18O and 2.40 Â‰ for 13C, while these values are 0.29 Â‰ for 18O and 0.55 for 13C for the growth line. Based on one-tailed t-tests with a 0.05 level of significance, there is a statistically significant difference between the mean 18O value of -1.28 0.80 Â‰ for the ontogenetic sequence and -0.73 0.29 Â‰ for the growth line, and between the mean 13C value of -1.28 2.40 Â‰ for the ontogenetic sequence and -0.31 0.55 Â‰ for the growth line. The sample taken from the E2 concretion returned a 18O value of -1.18 Â‰ and a 13C value of 0.18 Â‰. Three cement samples also returned values, shown on Figure 35.
124 FIGURE 31 Â—Sclerochronology of Eutrephoceras Specimen E2 The minor element sclerochronology of Eutrephoceras specimen E2 shows clearly the relationship between diagenetic alteration of shell and cementation. Solid vertical lines, indicating the presence of cement, coincide w ith relative maxima in Fe/Ca, Mg/Ca, and Mn/Ca, which are minima in Na/Ca.
125 FIGURE 32 Â—Stable Isotope Sclerochronology of Eutrephoceras Specimen E2 The stable isotope sclerochronology of the Eutrephoceras specimen shows parallel curves for 18O and 13C, with nearly all minima and maxima coinciding. Both curves show greater fluctuations before distance = 30 mm. Once again, solid vertical lines indicate the location of cement.
126 FIGURE 33 Â— 18O Versus 13C for Eutrephoceras Specimen E2 13C, Â‰ vs. PDB 18O, Â‰ vs. PDB The relationship between 18O and 13C is positive, with an r2 value of 0.673 and a p value of 4.52 x 10-4,. The majority of data points cluster from -2Â‰ to 0.5Â‰ for 13C and -0.5Â‰ to -1.5Â‰ for 18O.
127 FIGURE 34 Â—Calculated Paleotemperature and Paleosalinity for Eutrephoceras Specimen E2 Calculated paleotemperature shows several fluctuations, with the largest being spaced at 55, 105, and 170 mm from the protoconch. Paleosalinity coincides with the isotopic trends for the first half of the ontogenetic sequence.
128 3.4 Discussion 3.4.1. Inoceramus: The slight negative correlation between 18O and 13C in Inoceramus specimen I2 (Figure 24) is characteristic of bivalves with a slow rate of metabolism (Ivany et al., 2003). Instead of reflecting metabolism, the isotopic signature in such mollusks reflects environmental parameters such as salinity and temperature. In the Western Interior Seaway, a specimen of the bivalve Artica ovata (Fatherree, 1995) also showed a negative correlation between stable isotopes. This pattern was noted for the Recent bivalve Adamussium colbecki an Antarctic scallop (Barrerra et al., 1990). The Recent Mercenaria mercenaria specimen from the Long Island Sound examined by Elliot et al. (2003) also showed such a correlation, as did the Eocene Cucullaea raea after 6 mm of ontogenetic growth (Dutton et al., 2002). In contrast, Mercenaria mercenaria specimens found farther south showed a positive correlation between 18O and 13C (Elliot et. al., 2003), as did the Cucullaea raea before 6 mm growth. Previous studies of Inoceramus also revealed positive correlations between 18O and 13C. Tourtelot and Rye (1969) found a positive correlation between stable isotopes in both the aragonitic and calcitic layers of an Inoceramus specimen, though their sequences for aragonite and calcite were limited to only had nine and ten data points, respectively. The ontogenetically earliest three of eight samples taken by Fatheree (1995) showed a positive relationship 18O and 13C, whereas the ontogenetically latest four showed a negative correlation. Whittaker et al. (1988) showed a similar pattern for a contemporaneous (but farther north) Inoceramus Of the 25 samples taken from Inoceramus specimen I2, the first six to eight show a positive relationship between 18O and 13C (Figure 23). This is likely the signature of a metabolic rate that decreases with
129 age, which is common in bivalves as energy in adulthood is redirected to reproductive maturation and spawning (Ivany et al., 2003). The inoceramid used in Fatheree et al. (1995) was from the Baculites compressus biozone in South Dakota, as was the Inoceramus specimen I2 used in this study. Both show 18O and 13C related positively for the first ~ 15 cm of (time-averaged) growth, suggesting that metabolic rate decreases at approximately the same time in each specimen. Interpretations of ontogenetic trends in 18O, 13C, and calculated temperature are hampered by the time-averaging present in the data. The 22.5-degree total temperature range of 26.3 to 48.8 oC (Figure 25) is clearly unrealistic for a shallow ocean during a warm greenhouse climate interval. However, two more realistic temperatures can be found on the paleotemperature curve for the Inoceramus 34.0 and 26.4 oC, at the two relative minima. While it should be remembered that these temperatures are influenced time-averaging inherent in the slowly deposited nacreous structure, they are clearly different from the remainder of the temperature data points. These points appear to represent marine conditions typical of the overlying water mass. These could be initiated by seasonal changes in oceanic circulation which produce a mixing of the water column. The length of such an interval with respect to the length of intervals with bottom-water isotopic signatures is unknown, because the Inoceramus could slow shell precipitation at such times and therefore produce an isotopic record biased towards bottom-water conditions.
130 While intervals of bottom-water can be identified in the sclerochronology of Inoceramus specimen I2, they cannot be readily explained. The heavy 13C and light 18O values are typical of Western Interior Seaway epifauna, with 13C and 18O values of 0.77 to 3.12Â‰ and -2.10 to -5.34, respectively, found for Anomia On the other hand, Inoceramus remains found outside of the Western Interior Seaway do not show such isotopic ratios. For instance, those found in Mid-Late Campananian deep-ocean environments in the South Atlantic produced average 13C and 18O values of 1.38 0.05Â‰ and 0.70 0.14Â‰, respectively (Saltzman and Barron, 1982). Therefore, it is unlikely that the isotopic ratios in the Inoceramus represent biological factors peculiar to Inoceramus. Therefore, the bottom-water represents an isotopically unique environment. An interesting observation with regards is that the salinity recorded by Inoceramus I2 stays close to normal marine conditions (~33Â‰) throughout ontogeny. However, using the 18O value of -1.27Â‰ for the Western Interior Seaway and assuming a decrease of 1Â‰ in w for every 5Â‰ increase in salinity (Epstein and Mayeda, 1953), in order to bring the Inoceramus paleotemperature down the ~30 oC necessary for shell precipitation. Even if the salinity equation used in this study is discarded, however, using the 18O value of -1.27Â‰ for the Western Interior Seaway to reach realistic paleotemperatures for the Inoceramus salinities in excess of 58Â‰ are needed, which would be inhospitable to Anomia Therefore, salinity is likely not the cause for the disparity between bottom-water and the overlying water mass. If instead, the salinity value is accepted, 18O of the bottom-water would have to be -3.70Â‰ to produce realistic paleotemperatures. An absurdly depleted freshwater input of -78Â‰ is needed to produce this value, and this would surely leave a signature on the Sr/Na ratios of the shells.
131 Another mechanism for reaching this value is unknown, as changing the signal of freshwater between -5 and -25Â‰ does not significantly affect the 18O result for seawater, and increasing the quantity of freshwater input would lower the 18O but also change salinity and provide light 13C. The 13C values of the epifauna are equally difficult to explain. Escape of methane present in the sediments would contribute 13C on the order of -15 to -20Â‰, consistent with the 13C values of shells for infaunal organisms but not those for epifaunal organism s. Addition of freshwater would likewise contribute negative 13C isotopes. Ocean anoxia is know to correlate with heavy 13C values in the unoxidized organic carbon, but how these values could be incorporated in molluscan shell is unknown. Therefore, at this time, it must be concluded that the light 18O and heavy 13C of the molluscan epifauna represent a distinct geochemical environment, without explanation, that may at times be mixed or replaced by water from the overlying water mass. The length of cycles present in 18O, 13C, and calculated temperature are impossible to interpret numerically as it is unknown how many sub-layers within the thin aragonitic shell each sampling penetrated and the amount of time each layer represents (which may differ between layers). These ambiguities could be circumvented if a specimen could be sampled, using a microscope-mounted drill, at a fine enough scale. Considering that the entire aragonitic layer for specimen I2 is ~1 mm thick, this does not seem feasible. A better alternative is to find Inoceramus specimens with intact outer calcitic layers, which accreted along the growth axis, and therefore can be sampled throughout ontogeny. The prismatic calcite layer can unfortunately be fragile, as it is usually separated from the aragonitic layer and fragmented, but sampling a reasonably
132 large calcitic shell piece (that can be readily oriented with respect to ontogeny) would resolve many questions about the bivalve. 3.4.2. Baculites: The slight positive correlation between 18O and 13C (Figures 28 and 29) is characteristic of a mollusk that is secreting shell that is influenced by metabolic CO2, usually implying a rapid metabolic rate (Ivany et al., 2003). A negative correlation between these two variables was also present for Baculites specimens from the Western Interior Seaway examined by Tourtelot and Rye (1969) and Forester et al. (1977). However, Whittaker et al. (1988) found well-defined negative correlations between stable isotopes in Baculites It is also present in the first few samples of the Baculites studied by Fatherree et al. (1998). Their samples taken later in the ontogeny of Baculites showed a negative correlation, which most likely indicates a decrease in the baculitidÂ’s rate of growth. A useful follow-up study would be examining the relationship between 18O and 13C with respect to the diameter of the baculite, preferably using fossils with longer contiguous shell records. The fluctuations in 18O, salinity, and temperature do not appear to be significant, and imply that the baculitid was living in the upper/intermediate water mass for the time span represented in the shell precipitated. The minima in 13C are not associated with changes in salinity, so likely do not represent migration into bottom-water. These fluctuations could be due to fluctuations in dissolved inorganic carbon within the water column, seasonal changes in food source, or alteration that is not coincident with minor element alteration. The temperature recorded by Baculites specimen B7, excluding the outlier of 24.2 oC at 25 mm from the ontogenetically earliest sample (a product of an unusually high Na/Ca ratio) ranges from 20.2 to 22.3 oC. This range represents reasonable living
133 conditions for a mollusk, and reasonable paleotemperatures for a shallow marine setting during a greenhouse climate interval. Forester et al. (1977) derived a temperature range from 17 to 25 oC for a 10-cm Baculites compressus var. robinsoni of the Western Interior Seaway. Fatherree et al. (1998) found an even greater temperature range, 19.7 to 29.7 oC, for their 44-cm ontogenetic sequence of a Baculites compressus found at Game Ranch. Because the temperature range for that specimen depends on the decrease in calculated temperature through ontogeny, within a 2.5-cm segment, however, the temperature difference is 0.4 to 5.8 oC, most often ~2.5oC. This is comparable to the range for baculitid B7. Because of the truncated temp erature range, the ontogenetic growth in the specimen likely represents less than one year, as is further suggestede by Fatherree et al.Â’s (1998) analysis. Recent Nautilus in the wild grows 9-44 mm/yr, with 24-44 mm/yr for adolescent individuals (Saunders, 1983). This should be considered a minimum growth rate for the Baculites because Nautilus must precipitate shell in a cold-water, high-pressure environment. Both of these physical factors are correlated with slower shell precipitation in Recent mollusks (Mann, 1992). 3.4.3. Eutrephoceras: Compared to the Eutrephoceras specimens studied by Landman et al. (1983), the Eutrephoceras in this study has a similar, but statistically significant, positive correlation between 18O and 13C (Figure 33). Recent Nautilus individuals raised in an aquarium instead show generally negative correlations, except for the first few millimeters of growth (Landman et al., 1984). This cannot be the effect of changes in feeding habits, as the majority of the ontogenetic sequence for the aquariaraised specimens was represented by pre-hatching growth. Whether the 13C of the aquarium water changed over the period of study is unknown, as is the general health of
134 the organisms, who died shortly after hatching and precipitated abnormally-shaped shells. As in the Nautilus and in the Eutrephoceras studied by Landman et al. (1983), the Eutrephoceras specimen E2 shows an increase to heavier isotopes in the first few centimeters of growth. In addition, the variability in isotopes prior to a distance of 35 mm from the E2 protoconch is low. This suggests a protected environment for the young nautiloid, presumably the egg sac. Through ontogeny, the Eutrephoceras shell shows slowly decreasing paleosalinities, likely reflecting offshore migration, as in Recent Sepia (Bettencourt and Guerra, 1999). With paleosalinities of ~27Â‰ during the first 75 mm of phragmacone accretion, these are comparable to the salinities calculated for Placenticeras, so likely represent the uppermost waters of the Western Interior Seaway. The sharp temperature drop prior to 35 mm could represent the migration out of a nearplanktic mode of life into one where the organism is living in colder water and swimming actively through the water column, where it accumulates both seawater carbonate and metabolic carbon with slightly varying isotopic signature. If the three largest temperature peaks on Figure 34 represent an annual cycle, the Eutrephoceras is growing at 60-80 mm in a year, slightly higher than the average growth rate for adolescent Nautilus and comparable to the growth rate for the cuttlefish Sepia offinalis living off the coast of Spain (Bettencourt and Guerra, 1999). Because the habitat of the Eutrephoceras is determined to be warm-water, the growth rate for Sepia is realistic. The 13C curve for Eutrephoceras specimen E2 shows a 13C range of -4.2 to 0.4Â‰, comparable in values and range to the Eutrephoceras in Landman et al. (1983) and in range alone to Nautilus (Landman et al., 1994). There is a single very negative 13C
135 excursion, late in ontogeny, which likely represents a migration into the bottom-water, because the salinity increases dramatically at the same time. Other excursions at 75 and 105 mm into this bottom water may be recorded by the 13C and salinity curves, with lower-amplitude 13C deviations. Why the Eutrephoceras would migrate into the bottomwater is a good question. It is possible that a preferred food source was present in the benthic sediments, and if this is the case, this research supports the notion of nektobenthic ammonites hovering above the seafloor when feeding. Another potential explanation is that the bottom-waters provided refuge from vertebrate predators during times of susceptibility, such as spawning or septal secretion. On the other hand, the signatures may instead record mixing events with the light18O bottom water.
136 4. CONCLUSIONS When performing stable isotope sclerochronology, or when using stable isotopes in molluscan shell for paleoclimate proxies, diagenetically altered shell must be avoided. The results of this study suggest that for paleotemperature reconstruction based on the isotopic analysis of aragonite, one must be selective. Specimens preserved in shale are preferable, as shown by the Â“Mode of PreservationÂ” suite and the higher standard deviations for paleotemperatures derived from fossils found in concretions (e.g., Trask Ranch Inoceramus versus Game Ranch Inoceramus ). In ammonites, phragmacones rather than septa should be sampled, given the greater likelihood of alteration in the latter. Opalescent or non-opalescent shell is acceptable, but color appears to have a slight effect on 18O which may affect diagenetic alteration. For the most part, 18O values are fairly robust even in the presence of cement, although, as seen at the Trask Ranch, the cementation phase may be a crucial factor in that later, meteoric cements can have a substantial influence on 18O. Based on the analysis, a series of minor-element filters were developed for aragonitic shell at the three sites. Anomalously low 18O values resulted from Sr/Ca ratios > 1.8 mMol/Mol, Na/Ca ratios > 10 mMol/Mol, Mn/Ca ratios < 11 mMol/Mol, Mg/Ca ratios < 6.5 mMol/Mol, and Fe/Ca ratios < 7 mMol/Mol. These limits were derived for the Kremmling sampling site, which had the greatest quantity of altered shell. Comparable values exist for the Trask Ranch site, but more data points of shell with altered 18O values are needed to define useful limits. The results for alteration of aragonitic 18O should not be extended to calcite without separate
137 investigation of calcitic mollusks, because the different crystal structure of calcitic shells will react differently to the influx of diagenetic waters. To glean information about paleoproductivity, molluscan diet, or the presence of methane using 13C ratios, a different set of criteria apply. Shale or concretions may be used, so long as neither contains cement directly in the shells. Septa and phragmacone samples both provide useful information, as most of the difference in isotopes between septa and phragmacone samples was in 18O. Opalescence and shell color had little bearing on 13C values for the sites investigated. Furthermore, the concentrations of certain minor elements, such as K, Na, and Al, appear to be quite robust. Sr is also robust when meteoric water is not implicated in diagenesis. These elements are not readily altered by the same diagenetic processes that affect 18O and 13C. Other minor elements, such as Fe, Mg, and Mn, are easily altered. Implementation of an empirically-derived Sr/Ca-Mg/Ca filter eliminated isotopically light, altered specimens. When these data points were removed, fields emerged on stable isotope cross-plots for each genus investigated. The confidence limits for the benthic bivalve Inoceramus did not overlap the nektic ammonites Baculites, Placenticeras, and Hoploscaphites implying that the environments were distinct. Calculations from the data support a very light 13C, methane-rich benthic habitat. The salinity figure for the intermediate/upper water is below normal salinity and the salinity figure for the bottom-water is close to normal salinity. There is no evidence for a distinct surface water mass, as a gradational series of paleosalinities and paleotemperatures were derived for the genera present in the Baculites compressus/cuneatus biozones. These include:
138 (1) Game Ranch Baculites : S = 30.6 0.8Â‰, T = 20.9 4.9 oC (2) Trask Ranch Baculites: S = 29.9 2.0Â‰, T = 24.8 4.2 oC (3) Game Ranch Placenticeras: S = 28.1 1.1Â‰, T = 30.1 4.9 oC (4) Game Ranch Hoploscaphites : S = 27.3Â‰ (n = 1), T = 36.5 (n = 1) oC (5) Game Ranch Inoceramus: S = 31.1 1.9Â‰, T = 36.1 3.2 oC (6) Trask Ranch Inoceramus: S = 27.7 9.6Â‰, T = 31.5 4.9 oC (7) Game Ranch Nymphalucina : S = 31.7 0.6Â‰, T = 14.8 1.2 oC The clearly unrealistic paleotemperatures for the benthic genera such as Inoceramus (and possibly the Hoploscaphites as well) cannot be explained at present. Methane seeps, a feature of the Western Interior Seaway during the Campanian, would contribute isotopically light 13C like the concretions and cements, not the heavy values seen in shell for this dataset and in prior research. Manipulation of the values for salinity and 18O(freshwater) in order to produce reasonable paleotemperatures results in salinities and freshwater geochemistries that are as unrealistic as the paleotemperatures were. Shale and concretions are both viable data sources for strontium and sodium data, as are both septa and phragmacone samples of ammonites. Opalescent shell should be selected, and color may have some influence on the depletion of Sr/Ca ratios. The presence of cementation, however, generally need not worry the paleosalinity investigator, at least at the localities investigated in this study. 18O and 13C sclerochronology of mollusks screened by the minor element filter reveals that Inoceramus precipitates most of its shell in bottom waters of unusual isotopic composition. There are two excursions into more normal paleotemperatures, but these do not correlate with any changes in the 13C of the benthic organisms. Because Inoceramus
139 is sessile, these excursions must represent environmental changes. On the other hand, Eutrephoceras precipitates most of its shell in the upper/intermediate waters but shows excursions which likely reflect migration into the bottom waters. In the Eutrephoceras changes in 18O are concurrent with and of the same magnitude as changes in 13C. Baculites appears to remain in the upper/intermediate waters, but shows fluctuations in 13C that could represent oceanic productivity and/or the organismÂ’s food source.
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145 Walaszczyk, I., and Cobban, W., 2000, Special Papers in Paleontology: Inoceramid Faunas and Biostratigraphy of the Upper Turonian Â– Lower Coniacian of the Western Interior of the United States : Palaeontological Association, London, ## p. Whittaker, S., Kyser, T., and Caldwell, W., 1986, Paleoenvironmental geochemistry of the Claggett marine cyclothem in south-central Saskatchewan: Canadian Journal of Earth Sciences, v. 24, p. 967-984. Wright, E., 1987, Stratification and paleocir culation of the Late Cretaceous Western Interior Seaway of North America: GSA Bulletin, v. 99, p. 480-490. Zakharov, Y., Smyshlyaeva, O., Tanabe,K., Shigeta, Y., Maeda, H., Ignatiev, A., Velivetskaya, T., Afanasyeva, T., Popov, A., Golozubov, V., Kolyada, A., Cherbadzhi, A., and Moriya, K., 2005, Seasonal temperature fluctuations int he high northern latitudes during the Cretaceous Period: isotopic evidence from Albian and Coniacian shallow-water invertebrates of the Talavka River Basin, Koryak Upland, Russian Far East: Cretaceous Research, v. 5, p. 1-20.
147 APPENDIX A: SHELL ALTERATION MASS SPECTROMETER DATA Mode of Preservation Suite Preserved Directly in Shale: Sample Location Genus 18O, vs. PDB 13C, vs. PDB MP-1 Game Ranch, SD Placenticeras -3.58 -1.72 MP-2 Game Ranch, SD Placenticeras -1.26 -0.93 MP-3 Game Ranch, SD Placenticeras -2.90 -1.65 MP-4 Game Ranch, SD Inoceramus -3.05 4.32 MP-5 Game Ranch, SD Inoceramus -4.59 5.04 MP-6 Game Ranch, SD Baculites -0.35 -0.81 MP-7 Game Ranch, SD Baculites -3.09 1.44 MP-8 Game Ranch, SD Nymphalucina 0.39 1.02 MP-9 Game Ranch, SD Nymphalucina 0.04 -18.20 Preserved in Concretions: Sample Location Genus 18O, vs. PDB 13C, vs. PDB MP-10 Kremmling, CO Placenticeras -18.46 -3.99 MP-11 Kremmling, CO Placenticeras -15.51 -6.72 MP-12 Kremmling, CO Placenticeras -15.13 -7.44 MP-13 Game Ranch, SD Inoceramus -4.51 2.80 MP-14 Game Ranch, SD Inoceramus -3.35 -0.91 MP-15 Trask Ranch, SD Inoceramus -1.38 5.66 MP-16 Game Ranch, SD Baculites -1.61 -0.46 MP-17 Game Ranch, SD Baculites -0.64 -1.42 MP-18 Trask Ranch, SD Baculites -1.00 -1.98 MP-19 Trask Ranch, SD Nymphalucina -1.93 -2.68 MP-20 Trask Ranch, SD Nymphalucina -9.07 -13.00
148 APPENDIX A (CONTINUED) Shell Testing Location Suite Shell Taken from Septum: Sample Location Genus 18O, vs. PDB 13C, vs. PDB SC-1S Game Ranch, SD Placenticeras -3.71 -3.74 SC-2S Kremmling, CO Baculites -13.12 -8.64 SC-3S Kremmling, CO Placenticeras N/A N/A SC-4S Trask Ranch, SD Hoploscaphites -3.69 -8.36 SC-5S Trask Ranch, SD Baculites -2.02 -4.85 SC-6S Trask Ranch, SD Baculites -3.48 -10.07 SC-7S Trask Ranch, SD Baculites -2.96 -9.09 SC-8S Trask Ranch, SD Baculites -2.08 -10.08 SC-9S Trask Ranch, SD Baculites -3.59 -7.58 SC-10S Trask Ranch, SD Baculites -1.81 -2.47 Shell Taken from Phragmacone Adjacent to Septum: Specimen Location Genus 18O, vs. PDB 13C, vs. PDB SC-1P Game Ranch, SD Placenticeras -2.91 -2.67 SC-2P Kremmling, CO Baculites N/A N/A SC-3P Kremmling, CO Placenticeras -8.86 -14.18 SC-4P Trask Ranch, SD Hoploscaphites -3.64 -7.46 SC-5P Trask Ranch, SD Baculites -2.31 -3.76 SC-6P Trask Ranch, SD Baculites -2.19 -1.79 SC-7P Trask Ranch, SD Baculites -1.85 -14.66 SC-8P Trask Ranch, SD Baculites -1.71 -1.71 SC-9P Trask Ranch, SD Baculites -2.82 -6.29 SC-10P Trask Ranch, SD Baculites -1.36 -2.36
149 APPENDIX A (CONTINUED) Shell Color Suite Kremmling, Colorado, samples Sample Genus Color Class 18O, vs. PDB 13C, vs. PDB SC-1 Placenticeras Tan -16.17 -3.74 SC-2 Placenticeras Cream N/A N/A SC-3 Placenticeras Moccasin -15.58 -6.63 SC-4 Placenticeras Yellow -13.06 -7.01 SC-5 Placenticeras Opalescent White -15.01 -6.99 SC-6 Hoploscaphites Moccasin -14.65 -7.01 SC-7 Hoploscaphites Cream -11.15 -4.17 SC-8 Hoploscaphites Moccasin -14.36 -13.07 SC-9 Hoploscaphites Tan -14.28 -6.48 SC-10 Hoploscaphites Wheat -14.25 -5.62 SC-11 Baculites Cream -14.63 -6.14 SC-12 Baculites Brown -15.06 -8.29 SC-13 Baculites Cream -15.17 -8.15 SC-14 Baculites Wheat -12.66 -7.59 SC-15 Baculites Yellow -15.09 -7.12 SC-16 Inoceramus Tan -8.87 -0.88 SC-17 Inoceramus Wheat -13.30 -6.93 SC-18 Inoceramus Moccasin -14.47 -7.67 SC-19 Anomia Tan -5.34 0.77 SC-20 Anomia Seashell -3.92 1.84
150 APPENDIX A (CONTINUED) Shell Color Suite (Continued) Game Ranch, South Dakota, samples Sample Genus Color Class 18O, vs. PDB 13C, vs. PDB SC-21 Placenticeras Opalescent White N/A N/A SC-22 Placenticeras Opalescent White -3.45 -2.77 SC-23 Placenticeras Linen -3.61 -2.93 SC-24 Placenticeras Opalescent White -3.12 -3.27 SC-25 Placenticeras Opalescent Yellow -2.05 -1.89 SC-26 Hoploscaphites Moccasin -4.51 0.54 SC-27 Baculites Seashell -1.36 -1.97 SC-28 Baculites Opalescent White -0.39 -1.48 SC-29 Baculites Opalescent White -1.18 -0.65 SC-30 Baculites Linen -0.54 -0.91 SC-31 Baculites Opalescent White -1.93 0.44 SC-32 Inoceramus Grey -4.54 2.36 SC-33 Inoceramus Brown -4.22 5.24 SC-34 Inoceramus Orange -4.29 4.97 SC-35 Inoceramus Linen -5.26 5.80 SC-36 Inoceramus Seashell -3.98 4.47 SC-37 Anomia Grey -3.87 0.92 SC-38 Anomia Grey -2.10 3.12 SC-39 Nymphalucina Seashell 0.14 -0.29 SC-40 Nymphalucina Cream 0.42 1.03
151 APPENDIX A (CONTINUED) Shell Color Suite (Continued) Trask Ranch, South Dakota, samples Sample Genus Color Class 18O, vs. PDB 13C, vs. PDB SC-41 Hoploscaphites Tan -4.41 -1.10 SC-42 Hoploscaphites Moccasin -5.41 -7.22 SC-43 Hoploscaphites Linen -3.45 -2.91 SC-44 Hoploscaphites Orange -3.97 -7.40 SC-45 Hoploscaphites Opalescent Grey -3.11 -0.05 SC-46 Inoceramus Tan -3.46 3.31 SC-47 Inoceramus Opalescent White -3.07 1.43 SC-48 Inoceramus Moccasin -4.06 3.48 SC-49 Inoceramus Seashell -3.84 0.18 SC-50 Inoceramus Wheat -4.34 1.84 SC-51 Baculites Opalescent White -1.18 -2.43 SC-52 Baculites Opalescent Seashell -3.22 -5.17 SC-53 Baculites Seashell -2.27 -2.76 SC-54 Baculites Yellow -2.27 -6.33 SC-55 Baculites Brown -1.05 -2.34 SC-56 Drepanocheilus Wheat -5.66 -13.65 SC-57 Drepanocheilus Seashell -2.31 -3.78 SC-58 Drepanocheilus Grey -5.89 -16.54 SC-59 Anisomyon Orange -6.58 -10.76 SC-60 Anisomyon Seashell -6.54 -8.58
152 APPENDIX A (CONTINUED) Cementation Suite Kremmling, Colorado, samples Sample Shell Cement Concretion ( 18O, 13C), vs. PDB CEM-1 Hoploscaphite s Sparry yellow Grey (-12.93, -11.87) (-13.99, -5.92) (-10.64, -9.10) CEM-2 Hoploscaphite s None None (-13.50, -11.87) None None CEM-3 Placenticeras Sparry clear Tan (-14.45, -7.40) (-17.02, -4.64) (-13.71, -6.63) CEM-4 Baculites None Tan (-14.94, -8.00) None (-14.33, -6.54) CEM-5 Baculites None Tan (-14.68, -11.54) None (-12.62, -11.17) CEM-6 Baculites Agate moccasin Tan N/A (-6.97, -2.97) (-12.50, -6.39) CEM-7 Baculites Sparry white Grey (-14.89, -8.19) (-10.90, -8.52) (-14.07, -11.30) CEM-8 Baculites Sparry yellow Grey (-15.15, -10.19) (-8.00, -7.57) (-12.87, -13.36) CEM-9 Baculites 1. Blocky clear 2. Sparry clear None (-15.04, -6.90) 1. (-23.74, -3.59) 2. (-10.03, -7.55) None CEM-10 Baculites 1. Agate yellow 2. Blocky clear Tan (-14.43, -6.83) 1. (-14.04, -4.94) 2. (-14.34, -3.17) None
153 APPENDIX A (CONTINUED) Cementation Suite (Continued) Game Ranch, South Dakota, samples Sample Shell Cement Concretion ( 18O, 13C), vs. PDB CEM-11 Placenticeras None None (-3.68, -5.40) None None CEM-12 Placenticeras None Yellow-Brown (-4.62, -3.89) None (-1.72, -7.81) CEM-13 Baculites None Yellow-Brown N/A None (-1.66, -11.00) CEM-14 Baculites None None (-1.67, -0.73) None None CEM-15 Baculites (2 samples) None 1. Red-Brown 2. Dark Grey 1. (-0.53, -0.83) 2. N/A None 1. (-1.19, -6.83) 2. N/A Trask Ranch, South Dakota, samples Sample Shell Cement Concretion ( 18O, 13C), vs. PDB CEM-16 Hoploscaphite s 1. Sparry yellow 2. Sparry moccasin Dark grey (-1.85, -6.54) 1. (-9.24, -12.67) 2. (-4.24, -10.45) (-1.68, -17.75) CEM-17 Hoploscaphite s (2 samples) 1. Sparry yellow 2. Sparry tan Dark grey 1. (-3.19, -6.88) 2. (-2.46, -6.98) 1. (-4.53, -10.47) 2. (-8.66,-12.84) (-1.80, -18.86) CEM-18 Hoploscaphite s None Dark grey (-4.99, -10.34) None (-2.38, -19.14)
154 APPENDIX A (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples (continued) Sample Shell Cement Concretion ( 18O, 13C), vs. PDB CEM-19 Hoploscaphite s (2 samples) 1. Sparry moccasin 2. Sparry moccasin Dark grey 1. (-4.87, -7.95) 2. (-4.19, -7.18) 1. (-6.03, -10.58) 2. (-6.50, -10.21) (-1.86, -17.65) CEM-20 Hoploscaphite s None Grey N/A None (-1.69, -25.09) CEM-21 Baculites 1. Sparry tan 2. Blocky brown Grey (-1.06, -4.86) 1. (-1.05, -9.96) 2. (-4.38, -7.87) (-2.11, -19.21) CEM-22 Baculites (2 samples) 1. Sparry yellow 2. Blocky yellow Grey 1. N/A 2. (-1.25, -5.11) 1. (-5.73, -11.45) 2. (-4.04, -10.09) (-4.41, -19.91) CEM-23 Baculites 1. Blocky mocc. 2. Blocky seashell Grey (-5.69, -9.05) 1. (-11.98, -14.37) 2. (-13.78, -16.34) (-3.50, -19.60) CEM-24 Baculites Sparry yellow Dark Grey (-3.15, -11.34) (-1.95, -12.73) (-1.70, -19.84) CEM-25 Baculites Blocky yellow None N/A (-1.82, -19.48) None CEM-26 Baculites Sparry grey-brown Grey (-3.73, -8.49) (-1.82, -19.48) (-6.21, -10.47) CEM-27 Baculites Sparry linen Dark Grey (-2.24, -7.23) (-1.10, -16.97) (-1.35, -24.54) APPENDIX A (CONTINUED)
155 Cementation Suite (Continued) Trask Ranch, South Dakota, samples (continued) Sample Shell Cement Concretion ( 18O, 13C), vs. PDB CEM-28 Baculites Blocky, yellowmoccasin Dark grey (-3.07, -8.01) (-4.81, -21.00) (-1.29, -24.70) CEM-29 Baculites None Grey (-1.47, -1.31) None (-2.29, -18.58) CEM-30 Baculites 1. Sparry dark grey 2. Agate brown Grey (-2.96, -5.45) 1. (-1.72, -12.96) 2. (-8.55, -11.72) (-1.70, -18.64) CEM-31 Baculites Agate yellow None (-2.35, -2.51) (-10.20, -12.17) None CEM-32 Baculites Sparry seashell None (-5.21, -5.52) (-10.02, -12.67) None CEM-33 Baculites None Dark Grey (-2.58, -2.09) None (-4.02, -19.86) CEM-34 Baculites None Dark Grey (-3.16, -4.51) None (-1.24, -25.75) CEM-35 Baculites None Dark Grey (-0.98, -1.97) None (-1.62, -14.28)
156 APPENDIX B: SHELL ALTERATION ICP DATA Mode of Preservation Suite Preserved Directly in Shale Specimen [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) MP-1 349831.691N/A N/A MP-2 175693.342N/A N/A MP-3 373965.603N/A N/A MP-4 341289.398N/A N/A MP-5 322061.902N/A N/A MP-6 334993.853N/A N/A MP-7 370032.558N/A N/A MP-8 391581.568N/A N/A MP-9 321557.153N/A N/A Preserved in Concretions Specimen [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) MP-10 342648.817N/A N/A MP-11 357578.3271591.860 0.178 MP-12 396504.370165.661 0.017 MP-13 313047.021N/A N/A MP-14 384331.947N/A N/A MP-15 357487.581N/A N/A MP-16 290491.855106.879 0.015 MP-17 329805.680N/A N/A MP-18 387999.920N/A N/A MP-19 348750.500467.572 0.054 MP-20 286764.7504507.980 0.629 *weight percents normalized to 40% Ca
157 APPENDIX B (CONTINUED) Mode of Preservation Suite (Continued) Preserved Directly in Shale Specimen [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) MP-1 164.2950.337338.309 0.992 MP-2 N/A N/A167.558 0.978 MP-3 286.0900.549245.962 0.675 MP-4 N/A N/A139.411 0.419 MP-5 1916.9054.270179.928 0.573 MP-6 307.5770.659302.695 0.927 MP-7 340.5070.660276.961 0.768 MP-8 N/A N/A185.102 0.485 MP-9 108.3220.242238.344 0.760 Preserved in Concretions Specimen [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) MP-10 3589.2997.514153.669 0.460 MP-11 3426.1626.873183.978 0.528 MP-12 4207.6027.612310.269 0.803 MP-13 610.0691.398437.089 1.432 MP-14 115.7730.216310.451 0.828 MP-15 3721.6237.468186.998 0.536 MP-16 12977.51032.047461.101 1.628 MP-17 139.9360.304194.419 0.605 MP-18 N/A N/A194.544 0.514 MP-19 5955.41712.250257.469 0.757 MP-20 3092.7607.737591.085 2.114 *weight percents normalized to 40% Ca
158 APPENDIX B (CONTINUED) Mode of Preservation Suite (Continued) Preserved Directly in Shale Specimen [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) MP-1 106.4390.502199.801 0.417 MP-2 46.2720.435147.254 0.612 MP-3 161.3080.712404.205 0.789 MP-4 82.3430.398N/A N/A MP-5 95.3590.489285.207 0.647 MP-6 166.2580.8193239.452 7.063 MP-7 120.0080.535307.190 0.606 MP-8 804.5983.391N/A N/A MP-9 121.9450.626N/A N/A Preserved in Concretions Specimen [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) MP-10 2308.43011.1171762.292 3.757 MP-11 1500.1106.9237216.334 14.741 MP-12 1579.4436.5733931.915 7.243 MP-13 192.6181.0152249.453 5.249 MP-14 114.1520.490110.404 0.210 MP-15 744.1143.4352575.970 5.263 MP-16 1030.1815.8521184.273 2.978 MP-17 95.9910.48085.498 0.189 MP-18 264.7231.12626.294 0.049 MP-19 2546.29312.0486814.483 14.272 MP-20 3351.21119.285969.246 2.469 *weight percents normalized to 40% Ca
159 APPENDIX B (CONTINUED) Mode of Preservation Suite (Continued) Preserved Directly in Shale Specimen [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) MP-1 3902.40719.4492409.576 3.153 MP-2 1801.96317.8821237.669 3.225 MP-3 3410.73615.9013499.546 4.284 MP-4 3940.04420.1281823.674 2.446 MP-5 3636.22619.6852335.145 3.319 MP-6 3528.75618.3652212.174 3.023 MP-7 4009.19018.8902029.169 2.510 MP-8 2814.21612.5301449.045 1.694 MP-9 2142.85211.6191399.016 1.992 Preserved in Concretions Specimen [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) MP-10 577.9912.9411093.216 1.460 MP-11 344.6191.680651.877 0.835 MP-12 3103.77113.6481838.879 2.123 MP-13 3347.03118.6411833.716 2.681 MP-14 4178.66718.9562574.603 3.067 MP-15 3266.04115.9292584.284 3.309 MP-16 3350.21920.1079318.315 14.684 MP-17 3792.94720.0512397.838 3.328 MP-18 4238.46019.0462111.923 2.492 MP-19 1248.3596.241932.789 1.224 MP-20 2728.57516.5891290.938 2.061 *weight percents normalized to 40% Ca
160 APPENDIX B (CONTINUED) Shell Testing Location Suite (Continued) Shell Taken from Septum: Specimen [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) 1S 397800.760N/A N/A 2S 302918.706586.552 0.077 3S 275462.9812783.478 0.404 4S 339307.6291144.141 0.135 5S 293972.4371158.966 0.158 6S 323656.561870.411 0.108 7S 353154.550N/A N/A 8S 379448.01299.169 0.010 9S 328225.280224.715 0.027 10S 304005.309597.682 0.079 Shell Taken from Phragmacone Adjacent to Septum: Specimen [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) 1P 323301.687353.076 0.044 2P 394523.767486.131 0.049 3P 13893.955190.225 0.548 4P 307581.5491735.389 0.226 5P 289798.190891.545 0.123 6P 303252.508645.480 0.085 7P 318913.955537.746 0.067 8P 310820.113736.899 0.095 9P 314319.917231.145 0.029 10P 293918.6041086.639 0.148 *weight percents normalized to 40% Ca
161 APPENDIX B (CONTINUED) Shell Testing Location Suite (Continued) Shell Taken from Septum: Specimen [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) 1S 337.0610.608241.893 0.624 2S 4216.9329.986745.807 2.525 3S 14485.54537.723756.209 2.815 4S 1402.2022.964650.465 1.966 5S 408.6540.997458.002 1.598 6S 1445.9603.205675.592 2.141 7S 596.1961.211272.637 0.792 8S 294.2760.556326.919 0.884 9S 702.0571.534547.704 1.711 10S 811.7001.915536.863 1.811 Shell Taken from Phragmacone Adjacent to Septum: Specimen [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) 1P 5953.31613.209689.200 2.186 2P 4679.8218.509566.304 1.472 3P 534.42527.593196.770 14.525 4P 3701.2328.632998.568 3.330 5P 1833.1834.538360.167 1.275 6P 1243.1612.941658.346 2.226 7P 3108.6756.993546.688 1.758 8P 3081.6127.112470.134 1.551 9P 913.8282.086376.295 1.228 10P 1756.9554.288701.014 2.446 *weight percents normalized to 40% Ca
162 APPENDIX B (CONTINUED) Shell Testing Location Suite (Continued) Shell Taken from Septum: Specimen [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) 1S 165.9990.689164.926 0.303 2S 1573.9358.5745820.233 14.034 3S 3102.62018.5875411.270 14.349 4S 4785.93423.2763524.525 7.587 5S 1428.2198.017113.901 0.283 6S 1602.2548.169410.622 0.927 7S 10471.82648.932983.656 2.034 8S 465.9932.02766.291 0.128 9S 2525.54012.698844.126 1.878 10S 2497.08413.555398.261 0.957 Shell Taken from Phragmacone Adjacent to Septum: Specimen [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) 1P 1292.8386.5993199.795 7.229 2P 3127.00613.0806612.912 12.243 3P 216.89425.761174.509 9.174 4P 3838.15720.5923650.128 8.668 5P 2335.73213.300341.210 0.860 6P 5492.70429.890571.669 1.377 7P 8059.76541.7053192.408 7.312 8P 4881.98525.9191311.369 3.082 9P 3011.74915.8121636.809 3.804 10P 2041.62911.463492.919 1.225 *weight percents normalized to 40% Ca
163 APPENDIX B (CONTINUED) Shell Testing Location Suite (Continued) Shell Taken from Septum: Specimen [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) 1S 3690.89716.1762975.639 3.424 2S 628.3383.616523.399 0.791 3S 670.0994.241512.388 0.851 4S 3067.14315.7603425.384 4.621 5S 3264.90819.3631964.570 3.059 6S 5959.57732.1032099.138 2.969 7S 2431.04212.0021535.904 1.991 8S 4064.04818.6732228.468 2.688 9S 6641.44735.2782721.898 3.796 10S 7111.69640.7861783.532 2.686 Shell Taken from Phragmacone Adjacent to Septum: Specimen [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) 1P 3019.70916.28411566.121 16.376 2P 920.3004.067931.567 1.081 3P 284.50535.701604.503 19.917 4P 3295.05018.6771940.755 2.888 5P 3517.41521.1611997.610 3.155 6P 5232.18830.0812606.202 3.934 7P 7940.19043.4081531.817 2.199 8P 2746.38415.4052707.685 3.988 9P 2187.07112.1312827.012 4.117 10P 5139.49130.4872212.709 3.446 *weight percents normalized to 40% Ca
164 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Kremmling, Colorado, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) SC-1 349374.665N/AN/A SC-2 210798.358428.8660.081 SC-3 307749.064N/AN/A SC-4 324906.964N/AN/A SC-5 388851.043N/AN/A SC-6 336077.139231.9450.028 SC-7 233388.7442414.9110.414 SC-8 256015.593284.7860.044 SC-9 296636.1391137.9170.153 SC-10 346784.033N/AN/A SC-11 255766.4781426.7060.223 SC-12 391821.330N/AN/A SC-13 309157.385N/AN/A SC-14 196443.8552467.3860.502 SC-15 327370.577314.5960.038 SC-16 179071.4331857.4790.415 SC-17 120771.7962009.0810.665 SC-18 272407.3391657.1660.243 SC-19 245129.4452012.2110.328 SC-20 338296.486N/AN/A
165 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Game Ranch, South Dakota, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) SC-21 295002.574779.0890.106 SC-22 380815.313N/AN/A SC-23 377794.156N/AN/A SC-24 285378.708493.7170.069 SC-25 375552.472N/AN/A SC-26 350602.18988.5970.010 SC-27 286893.057N/AN/A SC-28 348429.480N/AN/A SC-29 307341.2791147.9630.149 SC-30 368493.489N/AN/A SC-31 346095.016N/AN/A SC-32 379592.814N/AN/A SC-33 346144.010N/AN/A SC-34 303721.408234.4360.031 SC-35 350303.529N/AN/A SC-36 351040.497N/AN/A SC-37 354576.098229.0180.026 SC-38 338869.682176.8700.021 SC-39 370022.686N/AN/A SC-40 333044.179268.2380.032
166 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Trask Ranch, South Dakota, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) SC-41 383656.252N/AN/A SC-42 314802.951120.1300.015 SC-43 336563.754272.6870.032 SC-44 327926.765431.8060.053 SC-45 344621.864183.8850.021 SC-46 367743.402N/AN/A SC-47 368017.078N/AN/A SC-48 382577.145N/AN/A SC-49 349892.589N/AN/A SC-50 384139.477N/AN/A SC-51 346954.297247.4610.029 SC-52 374739.380N/AN/A SC-53 292900.718921.4930.126 SC-54 354750.549440.1630.050 SC-55 369232.955N/AN/A SC-56 322742.995928.3380.115 SC-57 306012.3901902.7680.249 SC-58 363062.0121239.1450.137 SC-59 592092.4861893.6340.128 SC-60 310263.3921487.7020.192
167 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Kremmling, Colorado, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) SC-1 6736.994 13.833119.007 0.349 SC-2 3903.263 13.283446.898 2.174 SC-3 2759.682 6.433176.120 0.587 SC-4 9989.496 22.056181.576 0.573 SC-5 4047.950 7.468163.946 0.432 SC-6 4666.698 9.961352.146 1.075 SC-7 5025.051 15.4451215.893 5.343 SC-8 4336.310 12.150264.814 1.061 SC-9 7274.074 17.591807.516 2.792 SC-10 11367.810 23.515174.042 0.515 SC-11 4837.432 13.568838.281 3.361 SC-12 4392.651 8.042226.923 0.594 SC-13 4055.587 9.410216.167 0.717 SC-14 5199.664 18.9881221.966 6.380 SC-15 5293.590 11.600398.537 1.249 SC-16 3264.076 13.076983.965 5.635 SC-17 3826.494 22.7281014.966 8.619 SC-18 5829.126 15.350957.701 3.606 SC-19 1465.171 4.288502.938 2.104 SC-20 182.013 0.386180.520 0.547
168 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Game Ranch, South Dakota, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) SC-21 11119.928 27.0401085.274 3.773 SC-22 377.728 0.712288.124 0.776 SC-23 67.176 0.128281.042 0.763 SC-24 11255.772 28.293774.921 2.785 SC-25 1138.393 2.174301.653 0.824 SC-26 951.777 1.947549.251 1.607 SC-27 54990.386 137.499358.482 1.281 SC-28 429.027 0.883430.792 1.268 SC-29 13124.393 30.6331283.895 4.284 SC-30 136.915 0.267295.726 0.823 SC-31 399.480 0.828323.004 0.957 SC-32 348.335 0.658480.928 1.299 SC-33 396.158 0.821545.087 1.615 SC-34 8802.022 20.789569.099 1.922 SC-35 269.467 0.552387.858 1.136 SC-36 61.635 0.126330.524 0.966 SC-37 2319.393 4.692532.004 1.539 SC-38 1191.225 2.522420.055 1.271 SC-39 994.297 1.928413.204 1.145 SC-40 473.524 1.020525.450 1.618
169 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Trask Ranch, South Dakota, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) SC-41 878.332 1.642343.065 0.917 SC-42 560.224 1.277510.236 1.662 SC-43 1040.026 2.217348.456 1.062 SC-44 3153.780 6.899519.968 1.626 SC-45 907.823 1.890416.701 1.240 SC-46 375.105 0.732352.882 0.984 SC-47 350.843 0.684383.760 1.069 SC-48 250.910 0.470293.720 0.787 SC-49 484.413 0.993484.836 1.421 SC-50 154.620 0.289350.884 0.937 SC-51 621.354 1.285559.584 1.654 SC-52 267.156 0.511395.679 1.083 SC-53 1651.748 4.0451057.093 3.701 SC-54 5099.743 10.312624.870 1.806 SC-55 144.526 0.281333.893 0.927 SC-56 6788.838 15.089833.530 2.649 SC-57 2378.588 5.576902.531 3.025 SC-58 1655.949 3.2721000.435 2.826 SC-59 10936.007 13.2501526.556 2.644 SC-60 5306.503 12.269820.833 2.713
170 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Kremmling, Colorado, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) SC-1 1972.721 9.3182945.413 6.158 SC-2 2026.530 15.8643988.699 13.821 SC-3 1270.365 6.8126230.504 14.788 SC-4 2581.117 13.1104049.314 9.103 SC-5 1672.626 7.0985448.521 10.235 SC-6 1582.790 7.7727306.718 15.880 SC-7 2956.605 20.9052494.407 7.807 SC-8 2453.366 15.8144032.559 11.505 SC-9 2325.221 12.9354855.124 11.955 SC-10 2141.687 10.1914314.775 9.088 SC-11 1993.891 12.8655579.722 15.935 SC-12 1911.589 8.0518319.078 15.508 SC-13 1383.786 7.3866944.814 16.408 SC-14 2935.301 24.6583169.419 11.785 SC-15 1797.564 9.0616779.449 15.126 SC-16 4074.614 37.5491342.895 5.478 SC-17 2616.606 35.7532074.170 12.544 SC-18 2865.714 17.3605512.545 14.781 SC-19 2396.181 16.1311418.026 4.225 SC-20 2667.130 13.010526.068 1.136
171 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Game Ranch, South Dakota, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) SC-21 1326.876 7.4222942.568 7.286 SC-22 126.981 0.550180.025 0.345 SC-23 161.861 0.70778.945 0.153 SC-24 5449.457 31.5123517.102 9.002 SC-25 183.582 0.8072635.794 5.126 SC-26 994.923 4.6831260.325 2.626 SC-27 2497.682 14.3675775.334 14.704 SC-28 298.577 1.414347.127 0.728 SC-29 1190.107 6.3901739.087 4.133 SC-30 84.588 0.379302.604 0.600 SC-31 98.034 0.467152.352 0.322 SC-32 309.860 1.3474919.315 9.466 SC-33 270.770 1.2913134.235 6.614 SC-34 11160.331 60.637942.549 2.267 SC-35 276.651 1.30345.970 0.096 SC-36 452.250 2.12673.290 0.152 SC-37 1860.869 8.6611747.161 3.599 SC-38 1306.539 6.362783.941 1.690 SC-39 648.516 2.892329.873 0.651 SC-40 216.444 1.072N/A N/A
172 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Trask Ranch, South Dakota, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) SC-41 575.944 2.4772145.707 4.085 SC-42 2240.993 11.747475.724 1.104 SC-43 2782.707 13.644972.733 2.111 SC-44 6031.295 30.3512779.305 6.191 SC-45 1216.740 5.826974.129 2.065 SC-46 1021.474 4.584460.717 0.915 SC-47 1458.854 6.542582.723 1.157 SC-48 348.164 1.502232.611 0.444 SC-49 904.993 4.268455.948 0.952 SC-50 394.804 1.696130.099 0.247 SC-51 321.873 1.531N/A N/A SC-52 804.157 3.541244.546 0.477 SC-53 3537.012 19.928759.422 1.894 SC-54 12247.372 56.9723563.514 7.337 SC-55 628.403 2.809246.420 0.487 SC-56 5729.899 29.2975775.688 13.071 SC-57 6623.041 35.7151543.848 3.685 SC-58 2741.765 12.4621749.631 3.520 SC-59 13388.800 37.3167764.048 9.578 SC-60 2694.561 14.3324623.775 10.885
173 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Kremmling, Colorado, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) SC-1 706.544 3.5261493.954 1.957 SC-2 3390.397 28.041384.189 0.834 SC-3 306.451 1.736544.015 0.809 SC-4 374.077 2.007754.795 1.063 SC-5 1734.972 7.7791422.817 1.675 SC-6 345.030 1.790576.458 0.785 SC-7 4594.785 34.324369.622 0.725 SC-8 369.586 2.517467.831 0.836 SC-9 420.889 2.474657.507 1.015 SC-10 254.623 1.280656.443 0.867 SC-11 1212.344 8.264456.583 0.817 SC-12 448.175 1.994819.504 0.957 SC-13 285.333 1.609511.231 0.757 SC-14 2246.541 19.938384.357 0.896 SC-15 358.141 1.907600.895 0.840 SC-16 3531.446 34.383529.702 1.354 SC-17 809.730 11.689221.732 0.840 SC-18 803.904 5.145554.923 0.933 SC-19 1735.618 12.345982.662 1.835 SC-20 2457.735 12.6661240.698 1.679
174 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Game Ranch, South Dakota, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) SC-21 3084.444 18.2292567.832 3.985 SC-22 3718.036 17.0223027.965 3.640 SC-23 3937.584 18.1723002.582 3.638 SC-24 2470.400 15.0932518.660 4.040 SC-25 3165.385 14.6953544.326 4.320 SC-26 3828.344 19.0382000.966 2.613 SC-27 3498.948 21.2632083.027 3.324 SC-28 4338.181 21.7071937.749 2.546 SC-29 3608.656 20.4712389.502 3.559 SC-30 4533.102 21.4482597.124 3.226 SC-31 4128.452 20.7971863.390 2.465 SC-32 3924.948 18.0272324.538 2.803 SC-33 3546.025 17.8613980.821 5.264 SC-34 3646.641 20.9332623.239 3.954 SC-35 4065.437 20.2341799.189 2.351 SC-36 4150.104 20.6123250.576 4.239 SC-37 2970.007 14.6041424.169 1.839 SC-38 3362.519 17.3001336.423 1.805 SC-39 2839.399 13.3791493.068 1.847 SC-40 2508.917 13.1341473.977 2.026
175 APPENDIX B (CONTINUED) Shell Color Suite (Continued) Trask Ranch, South Dakota, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) SC-41 3504.255 15.9253265.464 3.896 SC-42 4861.709 26.9264260.665 6.196 SC-43 8975.105 46.4932648.529 3.602 SC-44 1760.631 9.3612212.598 3.089 SC-45 4285.288 21.6802388.933 3.173 SC-46 3941.349 18.6861908.415 2.376 SC-47 5417.316 25.6642154.871 2.680 SC-48 4112.303 18.7412179.679 2.608 SC-49 3601.184 17.9442286.626 2.992 SC-50 3804.437 17.2672615.512 3.117 SC-51 3864.684 19.4202577.314 3.400 SC-52 3568.098 16.6013130.853 3.824 SC-53 4957.611 29.5101734.128 2.710 SC-54 2300.133 11.304592.935 0.765 SC-55 3944.085 18.6242813.711 3.488 SC-56 2382.854 12.8721656.773 2.350 SC-57 8502.651 48.4431671.584 2.501 SC-58 2169.675 10.4197309.292 9.216 SC-59 9058.639 26.6743659.690 2.829 SC-60 2842.429 15.9731575.591 2.325
176 APPENDIX B (CONTINUED) Cementation Suite Kremmling, Colorado, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) CEM-1S 255432.82771.184.484 CEM-1Ce 303879.50N/AN/A CEM-1Co 220810.481711.0511.509 CEM-2S 358874.98276.101.143 CEM-2Co 251093.161847.6210.928 CEM-3S 265065.62727.464.076 CEM-3Ce 475948.97N/AN/A CEM-3Co 179162.981766.7214.645 CEM-4S 625305.542580.286.129 CEM-4Co 211100.684971.6034.977 CEM-5S 350061.94N/AN/A CEM-5Ce 278865.48N/AN/A CEM-5Co 222344.011680.3711.224 CEM-6S 52036.78296.938.475 CEM-6Ce 339589.59N/AN/A CEM-6Co 190857.762513.6519.560 CEM-7S 339329.61534.682.340 CEM-7Ce 372392.56N/AN/A CEM-7Co 324670.051038.234.749 CEM-8S 335406.50N/AN/A CEM-8Ce 341787.32N/AN/A CEM-8Co 227985.952069.6913.483 CEM-9S 378031.27289.171.136 CEM-9Ce1 356061.91N/AN/A CEM-9Ce2 266343.28631.943.524 CEM-9Co 362867.17122.500.501 CEM-10S 361903.30N/AN/A CEM-10Ce1 388303.55N/AN/A CEM-10Ce2 379821.80N/AN/A CEM-10Co 299197.882180.7610.825
177 APPENDIX B (CONTINUED) Cementation Suite (Continued) Game Ranch, South Dakota, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) CEM-11S 261172.411819.5810.347 CEM-11Co 90588.343288.1953.909 CEM-11Cr1 237395.84394.692.469 CEM-11Cr2 226000.39100.900.663 CEM-12S 388705.07N/AN/A CEM-12Co 245278.191463.178.860 CEM-12Cr1 225573.17615.604.053 CEM-12Cr2 169693.24111.130.973 CEM-13S 380419.54106.250.415 CEM-13Co 237231.412053.7512.858 CEM-13Cr 236948.73286.251.794 CEM-14S 290700.00840.434.294 CEM-14Ce1 103306.32221.483.184 CEM-14Ce2 17070.41135.1511.759 CEM-14Cr1 25103.31876.9551.883 CEM-14Cr2 40110.251261.2846.702 CEM-15S 391032.82N/AN/A CEM-15Co1 268303.242156.2211.936 CEM-15Co2 92163.793094.0349.859
178 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) CEM-16S 372319.20308.461.230 CEM-16Ce1 348010.29N/AN/A CEM-16Ce2 367833.26259.471.048 CEM-16Co 300039.422645.3113.094 CEM-17S1 284559.41586.303.060 CEM-17S2 349902.11359.281.525 CEM-17Ce1 317855.38568.152.655 CEM-17Ce2 381884.20102.890.400 CEM-17Co 298747.212399.5211.929 CEM-18S 393776.54N/AN/A CEM-18Ce 399144.37259.380.965 CEM-18Co 260098.666439.2736.769 CEM-19S1 317955.32226.611.058 CEM-19S2 351780.35371.101.567 CEM-19Ce1 521438.36456.921.301 CEM-19Ce2 323274.26101.270.465 CEM-19Co 302066.992586.4712.717 CEM-20S 382850.85654.042.537 CEM-20Co 263178.456559.9937.020 CEM-21S 293049.191095.255.551 CEM-21Ce1 317672.23N/AN/A CEM-21Co 274184.032495.0413.515 CEM-22S1 281796.301014.275.346 CEM-22S2 336458.651515.346.689 CEM-22Ce1 280626.691540.348.152 CEM-22Ce2 370888.45N/AN/A CEM-22Co 264976.383974.4322.277 CEM-23S 277337.002329.7312.476 CEM-23Ce1 394020.73279.221.052 CEM-23Ce2 379758.14N/AN/A CEM-23Co 292270.672905.9214.767
179 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples (continued) Sample [Ca] ppm [Al] ppm Al/Ca (mMol/Mol) CEM-24S 272964.37426.632.321 CEM-24Ce 374382.05186.000.738 CEM-24Co 267054.503016.7316.777 CEM-25S 404485.34N/AN/A CEM-25Ce 370380.163651.0914.640 CEM-25Co 288819.663618.8218.609 CEM-26S 370368.96823.223.301 CEM-26Ce 294838.843018.7515.206 CEM-26Co 370133.19436.051.750 CEM-27S 313509.451406.786.664 CEM-27Ce 360938.20N/AN/A CEM-27Co 293772.242021.5810.220 CEM-28S 367916.87330.631.335 CEM-28Ce 227586.99141.910.926 CEM-28Co 227852.241858.5012.114 CEM-29S 333660.53970.364.319 CEM-29Co 289763.652262.8311.598 CEM-29Cr 338142.89591.502.598 CEM-30S 342594.961264.375.481 CEM-30Ce1 274004.45N/AN/A CEM-30Ce2 279716.771045.675.552 CEM-30Co 278435.073013.6816.075 CEM-31S 349977.93N/AN/A CEM-31Ce 350808.53N/AN/A CEM-32S 368450.73N/AN/A CEM-32Ce 335529.56N/AN/A CEM-33S 333255.241848.238.237 CEM-33Co 252382.592369.3113.943 CEM-34S 241088.47N/AN/A CEM-34Co 297050.082770.8913.854
180 APPENDIX B (CONTINUED) Cementation Suite (Continued) Kremmling, Colorado, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) CEM-1S 4952.4413.908582.62 0.091 CEM-1Ce 3752.218.858222.65 0.029 CEM-1Co 4490.1814.5871192.48 0.216 CEM-2S 13500.7426.987270.92 0.030 CEM-2Co 10301.2929.4301270.91 0.202 CEM-3S 2344.416.345372.91 0.056 CEM-3Ce 9026.8513.605224.80 0.019 CEM-3Co 5168.3320.6941211.73 0.271 CEM-4S 6919.877.938315.07 0.020 CEM-4Co 35258.23119.8131974.82 0.374 CEM-5S 6224.7712.756256.35 0.029 CEM-5Ce 5358.1113.783184.99 0.027 CEM-5Co 5655.2218.2461160.82 0.209 CEM-6S 1608.0822.168283.20 0.218 CEM-6Ce 11414.4924.112292.68 0.034 CEM-6Co 9809.5736.8701131.19 0.237 CEM-7S 3839.888.118539.74 0.064 CEM-7Ce 4255.778.198260.99 0.028 CEM-7Co 7070.9215.623749.87 0.092 CEM-8S 4197.528.977273.64 0.033 CEM-8Ce 4372.529.177188.24 0.022 CEM-8Co 4748.0414.9401315.89 0.231 CEM-9S 3942.207.481320.97 0.034 CEM-9Ce1 1483.532.989224.33 0.025 CEM-9Ce2 2690.767.247521.19 0.078 CEM-9Co 1401.352.770276.86 0.031 CEM-10S 6058.5712.009280.20 0.031 CEM-10Ce1 9109.8716.830234.90 0.024 CEM-10Ce2 1074.912.030241.38 0.025 CEM-10Co 13218.8831.6931063.35 0.142
181 APPENDIX B (CONTINUED) Cementation Suite (Continued) Game Ranch, South Dakota, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) CEM-11S 10183.9327.9721442.34 0.221 CEM-11Co 22768.73180.3012461.97 1.087 CEM-11Cr1 4073.1712.308423.42 0.071 CEM-11Cr2 1644.175.219346.32 0.061 CEM-12S 773.391.427322.47 0.033 CEM-12Co 28657.8183.8141541.98 0.251 CEM-12Cr1 15255.7648.515625.00 0.111 CEM-12Cr2 1516.006.409308.19 0.073 CEM-13S 553.871.044479.80 0.050 CEM-13Co 8455.5125.5682086.71 0.352 CEM-13Cr 851.552.578385.02 0.065 CEM-14S 18157.4644.807853.81 0.117 CEM-14Ce1 251512.431746.486437.05 0.169 CEM-14Ce2 5458.01229.363293.87 0.689 CEM-14Cr1 299573.598560.619916.13 1.460 CEM-14Cr2 36920.99660.3141493.93 1.490 CEM-15S 1062.481.949398.01 0.041 CEM-15Co1 11014.5329.4491498.51 0.223 CEM-15Co2 19198.16149.4282612.06 1.134
182 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) CEM-16S 1249.062.407435.43 0.047 CEM-16Ce1 2447.175.044345.91 0.040 CEM-16Ce2 5213.3610.167428.40 0.047 CEM-16Co 4763.1611.3881275.58 0.170 CEM-17S1 1483.173.739451.16 0.063 CEM-17S2 3249.966.663401.03 0.046 CEM-17Ce1 4655.3210.506408.06 0.051 CEM-17Ce2 1818.363.416321.83 0.034 CEM-17Co 4593.6111.0301259.95 0.169 CEM-18S 565.111.029285.96 0.029 CEM-18Ce 4260.187.657500.78 0.050 CEM-18Co 6202.8917.1081431.01 0.220 CEM-19S1 1015.032.290393.22 0.049 CEM-19S2 974.031.986336.07 0.038 CEM-19Ce1 10597.9814.580885.75 0.068 CEM-19Ce2 3362.327.461733.11 0.091 CEM-19Co 4800.1011.3991326.01 0.176 CEM-20S 500.360.938552.24 0.058 CEM-20Co 7025.3519.1491602.90 0.244 CEM-21S 1508.373.692475.97 0.065 CEM-21Ce1 47.190.107277.22 0.035 CEM-21Co 4781.5412.5101379.76 0.201 CEM-22S1 2047.935.213815.19 0.116 CEM-22S2 1250.872.667744.25 0.088 CEM-22Ce1 3883.439.927892.39 0.127 CEM-22Ce2 1072.542.074213.98 0.023 CEM-22Co 7773.5821.0452059.93 0.311 CEM-23S 4351.0411.2541102.74 0.159 CEM-23Ce1 4112.307.487399.04 0.041 CEM-23Ce2 5012.999.469211.90 0.022 CEM-23Co 6507.3815.9721712.64 0.234
183 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples (Continued) Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) CEM-24S 2006.905.274557.65 0.082 CEM-24Ce 1309.882.510323.60 0.035 CEM-24Co 5344.9014.3571596.19 0.239 CEM-25S 103.240.183283.57 0.028 CEM-25Ce 1665.793.226301.08 0.033 CEM-25Co 5375.2413.3511241.12 0.172 CEM-26S 2497.394.837448.43 0.048 CEM-26Ce 5861.8514.2621416.74 0.192 CEM-26Co 6339.4512.286468.31 0.051 CEM-27S 5588.0012.7861044.63 0.133 CEM-27Ce 2114.494.202191.74 0.021 CEM-27Co 4139.0410.1071259.02 0.171 CEM-28S 1116.532.177461.56 0.050 CEM-28Ce 2327.467.336312.40 0.055 CEM-28Co 4255.8913.3991245.74 0.219 CEM-29S 737.261.585382.61 0.046 CEM-29Co 5663.2514.0201304.50 0.180 CEM-29Cr 3382.427.176562.29 0.067 CEM-30S 2736.935.731805.32 0.094 CEM-30Ce1 1276.863.34371.29 0.010 CEM-30Ce2 6931.1617.775464.26 0.066 CEM-30Co 4968.0212.7991256.27 0.180 CEM-31S 1661.883.406956.27 0.109 CEM-31Ce 4575.429.356803.24 0.092 CEM-32S 4423.388.612185.87 0.020 CEM-32Ce 11133.9923.80459.69 0.007 CEM-33S 1501.393.232343.47 0.041 CEM-33Co 5290.2415.0371413.63 0.224 CEM-34S N/A N/A287.84 0.048 CEM-34Co 4690.1511.3261352.09 0.182
184 APPENDIX B (CONTINUED) Cementation Suite (Continued) Kremmling, Colorado, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) CEM-1S 1925.6012.4404209.74 12.038 CEM-1Ce 2204.2811.9702338.66 5.621 CEM-1Co 3500.2826.1593284.83 10.866 CEM-2S 2642.5112.1514333.35 8.820 CEM-2Co 7586.0149.8569212.94 26.800 CEM-3S 1086.866.7665189.71 14.301 CEM-3Ce 1766.716.1262497.75 3.833 CEM-3Co 2208.7320.3443135.77 12.784 CEM-4S 2657.127.01210423.82 12.176 CEM-4Co 3684.1428.7993798.09 13.142 CEM-5S 2258.4010.6465992.27 12.503 CEM-5Ce 1573.589.3122454.61 6.429 CEM-5Co 3735.7927.7273675.51 12.074 CEM-6S 577.6218.318246.42 3.459 CEM-6Ce 3695.4017.957647.83 1.393 CEM-6Co 3180.8627.5033887.91 14.879 CEM-7S 2411.3411.7274917.09 10.584 CEM-7Ce 3709.3916.4382710.49 5.316 CEM-7Co 3036.5415.4345409.66 12.170 CEM-8S 1713.138.4297196.78 15.673 CEM-8Ce 2476.2611.9562338.92 4.998 CEM-8Co 4684.4233.9073881.35 12.435 CEM-9S 2789.9912.1792781.31 5.374 CEM-9Ce1 503.972.3362059.01 4.224 CEM-9Ce2 970.866.015929.51 2.549 CEM-9Co 619.932.8192212.32 4.453 CEM-10S 1909.158.7057771.08 15.684 CEM-10Ce1 1700.057.2252001.87 3.766 CEM-10Ce2 448.861.9503297.99 6.342 CEM-10Co 2928.4516.1525831.75 14.237
185 APPENDIX B (CONTINUED) Cementation Suite (Continued) Game Ranch, South Dakota, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) CEM-11S 11234.9870.9884048.30 11.322 CEM-11Co 4141.7675.4495173.71 41.716 CEM-11Cr1 436.463.0341856.76 5.713 CEM-11Cr2 185.381.354348.50 1.126 CEM-12S 265.571.127264.06 0.496 CEM-12Co 6878.7446.2797669.42 22.839 CEM-12Cr1 1208.518.8412079.96 6.735 CEM-12Cr2 161.561.5711385.51 5.964 CEM-13S 339.541.473484.53 0.930 CEM-13Co 5107.0635.5254783.73 14.729 CEM-13Cr 311.362.168903.60 2.785 CEM-14S 2292.8513.0161515.90 3.809 CEM-14Ce1 15911.84254.17413506.79 95.499 CEM-14Ce2 557.9853.940372.86 15.954 CEM-14Cr1 13037.18857.02023881.43 694.867 CEM-14Cr2 2910.27119.73416724.11 304.551 CEM-15S 188.580.796756.39 1.413 CEM-15Co1 8167.9950.2373238.25 8.816 CEM-15Co2 4782.2585.62710352.44 82.045
186 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) CEM-16S 2746.0512.171783.25 1.537 CEM-16Ce1 925.284.3881522.48 3.195 CEM-16Ce2 3115.9113.9792982.59 5.923 CEM-16Co 13260.3972.9325819.61 14.167 CEM-17S1 3621.4221.0011411.27 3.622 CEM-17S2 8289.6039.0952397.31 5.004 CEM-17Ce1 3066.3215.9192473.52 5.684 CEM-17Ce2 1846.187.9781344.48 2.572 CEM-17Co 15531.8485.7943813.52 9.324 CEM-18S 926.513.883527.06 0.978 CEM-18Ce 4185.7217.3052549.51 4.666 CEM-18Co 16163.31102.5493596.46 10.100 CEM-19S1 2394.5912.4281539.06 3.536 CEM-19S2 4131.3719.3801493.92 3.102 CEM-19Ce1 3203.4210.1389155.12 12.824 CEM-19Ce2 1099.645.6132387.06 5.393 CEM-19Co 12223.0966.77513683.93 33.089 CEM-20S 2263.669.757425.34 0.811 CEM-20Co 15983.06100.2182752.25 7.639 CEM-21S 5109.2228.7711101.75 2.746 CEM-21Ce1 12088.7462.7971371.51 3.153 CEM-21Co 12978.9778.1152763.75 7.363 CEM-22S1 6911.1640.472794.24 2.059 CEM-22S2 6727.0232.994691.14 1.500 CEM-22Ce1 7815.2945.9571728.23 4.498 CEM-22Ce2 9454.3942.0661911.97 3.765 CEM-22Co 13359.7783.2013337.65 9.200 CEM-23S 4629.4127.5462878.12 7.580 CEM-23Ce1 2241.499.3885662.31 10.497 CEM-23Ce2 654.482.8448617.82 16.575 CEM-23Co 14039.6379.2703287.83 8.217
187 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples (continued) Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) CEM-24S 5749.5234.7591635.41 4.376 CEM-24Ce 10506.8046.3121647.69 3.215 CEM-24Co 15756.3597.3634240.37 11.598 CEM-25S 597.622.438225.38 0.407 CEM-25Ce 18500.8982.4303719.73 7.336 CEM-25Co 12874.9473.5633473.57 8.785 CEM-26S 4046.2418.0283240.42 6.391 CEM-26Ce 15324.6385.7726730.28 16.673 CEM-26Co 2889.9412.8853591.80 7.088 CEM-27S 7527.1439.6203907.32 9.103 CEM-27Ce 13019.1259.5237352.15 14.878 CEM-27Co 17161.9196.4043598.44 8.947 CEM-28S 2813.3512.619523.58 1.039 CEM-28Ce 7824.7256.7361484.89 4.766 CEM-28Co 13351.5296.6982170.49 6.958 CEM-29S 1115.735.51855.99 0.123 CEM-29Co 13707.0178.0626269.72 15.804 CEM-29Cr 1873.379.1423474.58 7.505 CEM-30S 4141.7219.9501576.25 3.361 CEM-30Ce1 13108.5678.9472087.25 5.564 CEM-30Ce2 2959.3917.4596204.11 16.201 CEM-30Co 16865.8599.9593175.60 8.331 CEM-31S 1302.996.1442656.91 5.545 CEM-31Ce 798.183.7557422.87 15.455 CEM-32S 2185.389.7888619.19 17.087 CEM-32Ce 1927.369.47920595.20 44.834 CEM-33S 3068.7115.196594.38 1.303 CEM-33Co 11965.3978.2363103.77 8.983 CEM-34S 231.951.58832.20 0.098 CEM-34Co 19755.00109.7452059.04 5.063
188 APPENDIX B (CONTINUED) Cementation Suite Kremmling, Colorado, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) CEM-1S 608.144.151446.82 0.801 CEM-1Ce 388.222.227304.26 0.458 CEM-1Co 608.654.806339.70 0.704 CEM-2S 546.982.657647.58 0.826 CEM-2Co 1713.6411.8991028.78 1.876 CEM-3S 696.954.584546.90 0.944 CEM-3Ce 481.711.765624.18 0.600 CEM-3Co 654.926.373202.35 0.517 CEM-4S 655.231.8271325.49 0.970 CEM-4Co 929.557.677317.10 0.688 CEM-5S 492.222.452725.64 0.949 CEM-5Ce 533.663.33694.09 0.154 CEM-5Co 649.285.091409.40 0.843 CEM-6S 416.3913.9511171.13 10.302 CEM-6Ce 526.522.703279.10 0.376 CEM-6Co 581.355.311337.13 0.809 CEM-7S 2052.3710.545707.50 0.954 CEM-7Ce 683.353.199381.89 0.469 CEM-7Co 567.913.050549.30 0.774 CEM-8S 547.092.844663.57 0.906 CEM-8Ce 398.672.034286.08 0.383 CEM-8Co 606.634.639368.25 0.739 CEM-9S 636.252.934763.94 0.925 CEM-9Ce1 377.191.847356.28 0.458 CEM-9Ce2 512.193.353N/A N/A CEM-9Co 387.331.861137.54 0.174 CEM-10S 476.942.298663.14 0.839 CEM-10Ce1 427.461.919468.24 0.552 CEM-10Ce2 918.714.217142.32 0.172 CEM-10Co 477.012.780435.87 0.667
189 APPENDIX B (CONTINUED) Cementation Suite (Continued) Game Ranch, South Dakota, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) CEM-11S 1699.9711.3481123.33 1.969 CEM-11Co 1876.7736.121426.30 2.154 CEM-11Cr1 848.816.2341182.29 2.280 CEM-11Cr2 725.215.5951072.97 2.173 CEM-12S 3882.5417.4153061.82 3.606 CEM-12Co 1981.1014.082919.51 1.716 CEM-12Cr1 959.667.4171077.21 2.186 CEM-12Cr2 501.685.1541059.68 2.859 CEM-13S 4203.0219.2632069.59 2.490 CEM-13Co 2242.6816.4821530.01 2.952 CEM-13Cr 607.094.467653.35 1.262 CEM-14S 3579.8321.4703398.15 5.351 CEM-14Ce1 993.1516.761470.24 2.084 CEM-14Ce2 446.2045.5733578.30 95.956 CEM-14Cr1 582.6340.46513.02 0.237 CEM-14Cr2 896.4538.966309.72 3.535 CEM-15S 4865.3621.6932384.12 2.791 CEM-15Co1 1218.557.918906.31 1.546 CEM-15Co2 2040.5338.601444.73 2.209
190 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm SrCa (mMol/Mol) CEM-16S 3658.1910.43611408.96 4.498 CEM-16Ce1 160.442.4815896.43 0.211 CEM-16Ce2 243.883.43212967.74 0.304 CEM-16Co 551.837.65829633.70 0.842 CEM-17S1 2332.9512.64811950.54 3.753 CEM-17S2 1499.769.38218079.87 1.962 CEM-17Ce1 211.3818.43314743.31 0.304 CEM-17Ce2 209.587.2627233.90 0.251 CEM-17Co 577.647.26529420.97 0.885 CEM-18S 4946.0911.7219898.06 5.750 CEM-18Ce 291.114.98513187.86 0.334 CEM-18Co 554.1017.64837019.87 0.975 CEM-19S1 2561.3714.38110752.52 3.688 CEM-19S2 2818.0510.30912204.53 3.667 CEM-19Ce1 444.793.76325869.54 0.390 CEM-19Ce2 290.949.5749749.54 0.412 CEM-19Co 638.938.17036674.08 0.968 CEM-20S 3114.5116.13311052.71 3.724 CEM-20Co 587.007.97635714.57 1.021 CEM-21S 1591.7117.89313889.75 2.486 CEM-21Ce1 712.777.87015931.48 1.027 CEM-21Co 474.558.54326217.09 0.792 CEM-22S1 1949.9843.45020555.48 3.168 CEM-22S2 1945.4928.43518361.48 2.647 CEM-22Ce1 875.2245.71224092.61 1.428 CEM-22Ce2 426.244.68814076.35 0.526 CEM-22Co 442.7114.50333152.26 0.765 CEM-23S 1288.4317.17919312.15 2.127 CEM-23Ce1 263.689.40215082.80 0.306 CEM-23Ce2 255.651.47015073.05 0.308 CEM-23Co 529.267.86730301.44 0.829
191 APPENDIX B (CONTINUED) Cementation Suite (Continued) Trask Ranch, South Dakota, samples (continued) Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm SrCa (mMol/Mol) CEM-24S 3739.3823.8841538.88 2.581 CEM-24Ce 1238.995.7701205.27 1.474 CEM-24Co 1914.2112.497583.39 1.000 CEM-25S 3408.5314.6923061.08 3.464 CEM-25Ce 926.394.361721.52 0.892 CEM-25Co 959.095.790565.92 0.897 CEM-26S 2252.3610.6032561.66 3.166 CEM-26Ce 1207.397.140707.12 1.098 CEM-26Co 874.074.117602.84 0.746 CEM-27S 6268.1234.8581842.73 2.691 CEM-27Ce 551.092.662452.77 0.574 CEM-27Co 1330.677.897618.02 0.963 CEM-28S 4233.6020.0622772.22 3.449 CEM-28Ce 623.574.777283.21 0.570 CEM-28Co 1494.7111.437493.74 0.992 CEM-29S 4056.1921.1951506.57 2.067 CEM-29Co 1452.218.738582.05 0.920 CEM-29Cr 3006.7015.503243.90 0.330 CEM-30S 3000.7015.2711346.21 1.799 CEM-30Ce1 682.004.340539.89 0.902 CEM-30Ce2 680.854.244299.99 0.491 CEM-30Co 1085.386.796673.87 1.108 CEM-31S 5300.7226.4062090.25 2.734 CEM-31Ce 786.073.907358.32 0.468 CEM-32S 2828.2113.3831443.49 1.793 CEM-32Ce 492.662.560417.26 0.569 CEM-33S 4640.9024.2802195.65 3.016 CEM-33Co 1453.3210.040543.67 0.986 CEM-34S 2081.6515.0542043.12 3.879 CEM-34Co 1047.476.148708.97 1.093 CEM-24S 3739.3823.8841538.88 2.581
192 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES Baculites candidates Sample [Al] ppm Al/Ca (mMol/Mol) [Ca] ppm B2 2.5 365.812.063264065.56 B2 7.5 N/AN/A321462.40 B2 12.5 N/AN/A343369.70 B2 17.5 N/AN/A294905.20 B2 22.5 N/AN/A335379.87 B2 27.5 N/AN/A284469.30 B2 32.5 N/AN/A326394.41 B3 2.5 188.000.846330841.49 B3 7.5 N/AN/A355309.16 B3 12.5 N/AN/A369106.63 B4 2.5 N/AN/A170565.47 B4 7.5 N/AN/A364469.94 B4 12.5 N/AN/A305218.85 B4 17.5 N/AN/A367046.51 B4 22.5 N/AN/A362235.49 B4 27.5 N/AN/A344474.10 B4 32.5 N/AN/A381711.31 B4 37.5 N/AN/A346901.60 B4 42.5 278.850.764543356.45 B5 2.5 N/AN/A N/A B5 7.5 N/AN/A366027.98 B5 12.5 N/AN/A763881.69 B5 17.5 N/AN/A413460.84 B6 12.5 409.971.809337424.10 B6 17.5 125.860.598313332.14 B6 22.5 N/AN/A330895.94 B6 27.5 N/AN/A368588.90 B6 32.5 N/AN/A339138.45 B6 37.5 231.321.030334370.43 B7 2.5 223.580.397838018.58 B7 7.5 N/AN/A 406809.47 B7 12.5 156.610.688339064.25 B7 17.5 N/AN/A 53845.91 B7 22.5 N/AN/A210883.79 B7 27.5 N/AN/A478341.92
193 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Baculites candidates Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) B2 2.5 253.380.688542.61 2.107 B2 7.5 512.751.144427.00 1.362 B2 12.5 285.700.597300.75 0.898 B2 17.5 138.770.338246.24 0.856 B2 22.5 288.980.618397.57 1.216 B2 27.5 467.201.178771.03 2.780 B2 32.5 203.630.448365.25 1.148 B3 2.5 1549.543.360594.00 1.841 B3 7.5 N/AN/A202.63 0.585 B3 12.5 58.800.114251.90 0.700 B4 2.5 455.941.918277.64 1.669 B4 7.5 198.240.390316.33 0.890 B4 12.5 365.870.860519.55 1.746 B4 17.5 624.251.220422.99 1.182 B4 22.5 456.920.905443.68 1.256 B4 27.5 133.280.278319.08 0.950 B4 32.5 476.060.895204.51 0.549 B4 37.5 100.250.207290.00 0.857 B4 42.5 1329.011.755452.25 0.854 B5 2.5 N/AN/A N/A N/A B5 7.5 260.380.510268.07 0.751 B5 12.5 729.590.685514.90 0.691 B5 17.5 493.780.857228.26 0.566 B6 12.5 1864.203.963679.94 2.067 B6 17.5 604.981.385429.89 1.407 B6 22.5 596.921.294340.73 1.056 B6 27.5 458.020.891248.77 0.692 B6 32.5 632.021.337294.57 0.891 B6 37.5 1867.934.007624.41 1.915 B7 2.5 411.0790.352571.386 0.699 B7 7.5 112.1210.198305.127 0.769 B7 12.5 331.5260.701299.098 0.905 B7 17.5 N/AN/A69.551 1.325 B7 22.5 N/AN/A138.953 0.676 B7 27.5 203.8770.306272.128 0.583
194 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Baculites candidates Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) B2 2.5 1103.286.895121.96 0.337 B2 7.5 692.853.55761.34 0.139 B2 12.5 377.511.81416.95 0.036 B2 17.5 554.673.10426.15 0.065 B2 22.5 769.823.78899.04 0.216 B2 27.5 1166.876.76935.76 0.092 B2 32.5 736.393.72387.52 0.196 B3 2.5 1662.208.291415.16 0.917 B3 7.5 140.790.654 N/A N/A B3 12.5 225.821.010 N/A N/A B4 2.5 696.566.739745.32 3.192 B4 7.5 539.152.441301.33 0.604 B4 12.5 553.862.994696.80 1.668 B4 17.5 1403.976.3121076.20 2.142 B4 22.5 560.252.552365.53 0.737 B4 27.5 403.321.93246.49 0.099 B4 32.5 567.062.451490.47 0.939 B4 37.5 551.402.623123.12 0.259 B4 42.5 874.622.656686.58 0.923 B5 2.5 N/AN/A N/A N/A B5 7.5 338.171.525339.01 0.677 B5 12.5 852.531.842772.40 0.739 B5 17.5 325.041.297293.41 0.518 B6 12.5 569.222.784202.87 0.439 B6 17.5 227.851.20033.72 0.079 B6 22.5 192.820.96239.96 0.088 B6 27.5 133.890.59996.75 0.192 B6 32.5 173.270.843106.28 0.229 B6 37.5 309.151.526294.99 0.644 B7 2.5 689.491.35820.46 0.018 B7 7.5 279.84N/AN/A N/A B7 12.5 624.121.135N/A N/A B7 17.5 29.91N/AN/A N/A B7 22.5 48.373.038N/A N/A B7 27.5 300.82N/AN/A N/A
195 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Baculites candidates Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) B2 2.5 2745.5118.1271250.82 2.168 B2 7.5 3195.3717.3301814.69 2.584 B2 12.5 3280.4316.6572139.38 2.852 B2 17.5 2489.6314.7192248.10 3.490 B2 22.5 2753.3214.3132713.46 3.704 B2 27.5 2677.4616.4102143.82 3.450 B2 32.5 2803.3614.9752455.55 3.444 B3 2.5 3161.2616.6592336.08 3.232 B3 7.5 3347.2616.4252550.73 3.286 B3 12.5 3356.2815.8532458.28 3.049 B4 2.5 1789.7818.2951301.99 3.494 B4 7.5 3953.9818.9142360.86 2.965 B4 12.5 3451.7919.7172824.90 4.237 B4 17.5 4339.6420.6132089.54 2.606 B4 22.5 3984.0419.1763629.91 4.587 B4 27.5 4034.2420.4189932.54 13.199 B4 32.5 4945.7722.5902419.72 2.902 B4 37.5 4605.3223.1462106.24 2.779 B4 42.5 6871.0122.0472930.35 2.469 B5 2.5 N/AN/A N/A N/A B5 7.5 2386.7611.3694491.82 5.618 B5 12.5 5477.8412.50310180.48 6.101 B5 17.5 2857.6412.0504980.93 5.515 B6 12.5 3694.6419.0901809.70 2.455 B6 17.5 3643.6520.2741388.38 2.028 B6 22.5 3936.7620.7431843.46 2.550 B6 27.5 4443.7421.0201854.99 2.304 B6 32.5 3776.5219.4151856.95 2.506 B6 37.5 3968.6720.6941911.85 2.617 B7 2.5 9865.9120.5265495.74 3.002 B7 7.5 4594.9719.6932547.85 2.867 B7 12.5 3876.5519.9331946.12 2.627 B7 17.5 870.2428.178255.58 2.173 B7 22.5 2287.5918.9131297.76 2.817 B7 27.5 9865.9121.3505495.74 2.825
196 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Hoploscaphites candidates Sample [Al] ppm Al/Ca (mMol/Mol) [Ca] ppm S1 2.5 267.5061.921207305.573 S1 7.5 221.9820.800413260.421 S1 12.5 463.8271.842374873.236 S1 17.5 181.9010.670404235.535 S1 32.5 1233.9154.842379420.193 S1 37.5 845.6842.757456738.989 S1 42.5 335.8251.441346888.808 S1 47.5 302.0801.447310867.078 S1 62.5 783.0043.873300981.475 S1 67.5 1312.8104.583426500.180 S2 2.5 N/AN/A363074.242 S2 7.5 501.2742.114353040.889 S2 12.5 285.2781.234344306.458 S2 17.5 219.3091.132288390.323 S2 22.5 140.0320.560372052.545 S2 27.5 352.5311.426368066.327 Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) S1 2.5 1037.6943.591673.166 3.330 S1 7.5 991.0691.720884.817 2.196 S1 12.5 653.1551.250841.025 2.301 S1 17.5 526.4650.9341265.433 3.210 S1 32.5 1296.6032.451707.980 1.914 S1 37.5 1640.3222.576872.473 1.959 S1 42.5 701.6131.451731.966 2.164 S1 47.5 1241.7302.865859.870 2.837 S1 62.5 1420.4323.385773.337 2.635 S1 67.5 1473.3892.4781918.705 4.614 S2 2.5 373.2060.737534.245 1.509 S2 7.5 1310.5322.663613.555 1.782 S2 12.5 2192.5164.568473.918 1.412 S2 17.5 676.0551.682623.382 2.217 S2 22.5 634.1111.223460.938 1.271 S2 27.5 3331.1536.4921165.538 3.248
197 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Hoploscaphites candidates Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) S1 2.5 929.4457.399477.264 1.682 S1 7.5 2262.3919.034919.957 1.626 S1 12.5 1407.2346.195568.949 1.109 S1 17.5 895.4233.655464.788 0.840 S1 32.5 2468.56110.736954.553 1.838 S1 37.5 3976.39214.3671830.487 2.927 S1 42.5 1935.4959.207593.163 1.249 S1 47.5 1452.4617.710753.260 1.770 S1 62.5 2940.57816.1221473.613 3.576 S1 67.5 1995.2457.7201668.781 2.858 S2 2.5 747.7333.399333.517 0.671 S2 7.5 1382.1366.4601219.453 2.523 S2 12.5 3328.24615.9522018.030 4.281 S2 17.5 971.2185.557666.030 1.687 S2 22.5 801.7593.556489.688 0.961 S2 27.5 3972.15817.8092750.446 5.458 Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) S1 2.5 1680.08114.1302097.634 4.632 S1 7.5 3447.68114.5454458.938 4.939 S1 12.5 2998.69713.9464022.630 4.912 S1 17.5 3274.16414.1224434.066 5.021 S1 32.5 3435.72915.7883551.256 4.285 S1 37.5 5545.56421.1694098.000 4.107 S1 42.5 2998.49915.0713625.386 4.784 S1 47.5 2647.01414.8463056.276 4.500 S1 62.5 2667.38315.4512545.437 3.871 S1 67.5 4227.22517.2803902.494 4.189 S2 2.5 2812.52613.5064496.015 5.669 S2 7.5 2428.10411.9914250.387 5.511 S2 12.5 1970.7399.9793389.025 4.506 S2 17.5 2199.82913.2993635.913 5.771 S2 22.5 2612.65612.2434590.141 5.648 S2 27.5 2749.11213.0223636.406 4.523
198 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Eutrephoceras candidates Sample [Al] ppm Al/Ca (mMol/Mol) [Ca] ppm E2 2.5 N/AN/A357989.515 E2 7.5 N/AN/A392733.687 E2 12.5 N/AN/A316045.993 E2 17.5 N/AN/A343872.149 E2 22.5 N/AN/A379829.797 E2 27.5 N/AN/A339860.586 E2 32.5 N/AN/A358598.942 E2 37.5 N/AN/A386914.337 E2 42.5 N/AN/A415595.254 E2 47.5 N/AN/A321592.717 E2 52.5 N/AN/A268579.797 E2 57.5 N/AN/A371053.678 E2 62.5 N/AN/A333722.987 E2 67.5 N/AN/A344491.441 E2 72.5 N/AN/A302795.163 E2 77.5 N/AN/A386660.944 E2 82.5 N/AN/A719557.827 E2 87.5 281.2051.999209487.467 E2 92.5 N/AN/A262396.338 E2 97.5 N/AN/A295143.927 E2 102.5 124.7990.710261856.053 E2 107.5 N/AN/A315942.621 E2 112.5 N/AN/A426532.824 E2 117.5 N/AN/A380409.148 E2 122.5 N/AN/A N/A E2 127.5 N/AN/A358731.534 E2 132.5 N/AN/A381276.879 E2 137.5 N/AN/A389496.894 E2 142.5 N/AN/A307078.777 E2 147.5 N/AN/A355207.188 E2 152.5 N/AN/A329934.782 E2 157.5 N/AN/A321906.769 E2 162.5 N/AN/A350568.683 E2 167.5 N/AN/A344855.345 E2 172.5 N/AN/A370882.865 E2 177.5 N/AN/A119064.165
199 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Eutrephoceras candidates Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) E2 2.5 938.1911.880323.853 0.928 E2 7.5 3131.1025.719365.827 0.955 E2 12.5 5840.09313.256306.323 0.994 E2 17.5 2553.5035.327242.078 0.722 E2 22.5 327.9950.619172.459 0.466 E2 27.5 368.1580.777765.244 2.309 E2 32.5 6239.82712.48266.705 0.191 E2 37.5 43.6130.081208.561 0.553 E2 42.5 303.9570.525492.421 1.215 E2 47.5 277.3770.61974.623 0.238 E2 52.5 218.0640.58280.698 0.308 E2 57.5 1126.2522.177696.592 1.925 E2 62.5 8376.82018.006330.674 1.016 E2 67.5 1781.9723.71192.997 0.277 E2 72.5 328.4110.778126.692 0.429 E2 77.5 884.1071.640294.667 0.782 E2 82.5 2249.6562.243240.859 0.343 E2 87.5 634.1892.172254.076 1.244 E2 92.5 351.3990.961438.625 1.714 E2 97.5 674.8681.640713.208 2.478 E2 102.5 775.8792.126550.986 2.158 E2 107.5 675.6921.534587.231 1.906 E2 112.5 766.8881.2902956.035 7.108 E2 117.5 1037.4261.9561507.606 4.064 E2 122.5 N/AN/A N/A N/A E2 127.5 122.7700.246714.571 2.043 E2 132.5 111.7000.210602.870 1.622 E2 137.5 323.4700.596869.781 2.290 E2 142.5 893.4152.087719.905 2.404 E2 147.5 536.6471.084665.591 1.922 E2 152.5 63.1380.1371001.761 3.114 E2 157.5 1080.8452.409687.522 2.190 E2 162.5 1450.4852.968943.150 2.759 E2 167.5 121.7290.2531431.286 4.257 E2 172.5 39.5750.077494.127 1.366 E2 177.5 N/AN/A968.986 8.346
200 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Eutrephoceras candidates Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) E2 2.5 558.7082.5751596.912 3.258 E2 7.5 3359.35214.1154139.469 7.699 E2 12.5 4393.90922.9424555.007 10.527 E2 17.5 1501.2087.2044232.184 8.990 E2 22.5 525.5032.283564.516 1.086 E2 27.5 529.0752.569564.660 1.214 E2 32.5 7783.96235.8203775.783 7.691 E2 37.5 90.9740.388171.050 0.323 E2 42.5 525.2592.086371.867 0.654 E2 47.5 380.8641.954518.794 1.178 E2 52.5 792.0424.866327.559 0.891 E2 57.5 2761.97212.283992.663 1.954 E2 62.5 9996.10549.4293297.253 7.217 E2 67.5 987.7144.7311497.412 3.175 E2 72.5 712.6953.884213.278 0.514 E2 77.5 1412.7076.0291144.864 2.163 E2 82.5 3027.1176.9423259.342 3.309 E2 87.5 1130.2628.903659.651 2.300 E2 92.5 1348.8958.483249.326 0.694 E2 97.5 1396.0507.806401.265 0.993 E2 102.5 451.2862.844311.868 0.870 E2 107.5 3108.62116.2371080.125 2.497 E2 112.5 289.3451.119 N/A N/A E2 117.5 346.2701.5021932.354 3.710 E2 122.5 N/AN/A N/A N/A E2 127.5 126.9280.58434.516 0.070 E2 132.5 151.9220.65822.586 0.043 E2 137.5 229.7210.97394.090 0.176 E2 142.5 4813.70725.8681292.276 3.074 E2 147.5 203.0560.943205.688 0.423 E2 152.5 215.1641.07638.379 0.085 E2 157.5 167.2410.857398.627 0.905 E2 162.5 240.5801.132178.241 0.371 E2 167.5 91.2970.437 N/A N/A E2 172.5 136.1430.60696.542 0.190 E2 177.5 1023.24714.182 N/A N/A APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES
201 (CONTINUED) Eutrephoceras candidates Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) E2 2.5 3143.56615.3102815.277 3.600 E2 7.5 2433.35610.8022745.420 3.200 E2 12.5 2074.54511.4442159.821 3.128 E2 17.5 2337.64211.8522497.766 3.325 E2 22.5 3097.24114.2173382.274 4.076 E2 27.5 3127.36916.0432890.340 3.893 E2 32.5 1328.2746.4581727.350 2.205 E2 37.5 3673.19216.5523718.224 4.399 E2 42.5 4029.57616.9053791.570 4.176 E2 47.5 2677.89814.5182817.560 4.011 E2 52.5 2331.15215.1332297.579 3.916 E2 57.5 3101.72014.5743186.961 3.932 E2 62.5 891.2464.656854.129 1.172 E2 67.5 2635.39413.3382502.775 3.326 E2 72.5 2479.42214.2762627.486 3.972 E2 77.5 3043.54313.7243157.269 3.738 E2 82.5 5390.87913.0625796.172 3.687 E2 87.5 1792.08114.9151788.658 3.908 E2 92.5 2718.36518.0622343.992 4.089 E2 97.5 2872.46816.9682338.568 3.627 E2 102.5 2732.67218.1952296.197 4.014 E2 107.5 2539.85614.0162118.883 3.070 E2 112.5 6065.63124.7942974.800 3.193 E2 117.5 4048.76718.5563071.339 3.696 E2 122.5 N/AN/A N/A N/A E2 127.5 4169.40520.2643173.310 4.049 E2 132.5 4231.81719.3513415.773 4.101 E2 137.5 4656.53020.8443430.437 4.032 E2 142.5 2415.98913.7171728.667 2.577 E2 147.5 4109.15020.1693364.547 4.336 E2 152.5 4303.29922.7402895.533 4.017 E2 157.5 3467.89018.7822972.524 4.227 E2 162.5 4367.93221.7233176.304 4.148 E2 167.5 4073.74620.5963040.137 4.035 E2 172.5 3739.77617.5803621.499 4.470 E2 177.5 7042.681103.127863.113 3.318
202 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Nymphalucina and Anomia candidates Sample [Al] ppm Al/Ca (mMol/Mol) [Ca] ppm N1 2.5 N/AN/A383590.021 N1 7.5 N/AN/A362891.188 N1 12.5 N/AN/A398020.200 N1 17.5 N/AN/A392288.327 N1 32.5 N/AN/A323092.385 A1 2.5 N/AN/A358872.790 A1 7.5 N/AN/A384260.889 A1 12.5 N/AN/A374301.768 A1 17.5 N/AN/A353644.015 A1 32.5 313.5121.336349475.836 A1 37.5 N/AN/A373988.796 A1 42.5 278.2641.208342863.817 Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) N1 2.5 170.1060.318362.403 0.969 N1 7.5 67.6220.134234.074 0.662 N1 12.5 N/AN/A148.942 0.384 N1 17.5 N/AN/A131.907 0.345 N1 32.5 N/AN/A171.604 0.545 A1 2.5 918.1461.835323.444 0.924 A1 7.5 1451.1422.709209.154 0.558 A1 12.5 829.5411.590241.885 0.663 A1 17.5 709.1741.439156.098 0.453 A1 32.5 3036.5206.233486.185 1.427 A1 37.5 710.0921.362290.445 0.796 A1 42.5 3401.2927.116421.545 1.261
203 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Nymphalucina and Anomia candidates Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) N1 2.5 2285.2709.831N/A N/A N1 7.5 118.5490.539N/A N/A N1 12.5 121.4020.503N/A N/A N1 17.5 41.9210.176N/A N/A N1 32.5 71.6210.366N/A N/A A1 2.5 1163.8145.352645.626 1.314 A1 7.5 1212.1795.206868.040 1.650 A1 12.5 1190.9345.251508.333 0.992 A1 17.5 1388.5806.480679.623 1.404 A1 32.5 1525.3697.2031569.174 3.280 A1 37.5 1236.9425.458662.344 1.294 A1 42.5 1677.1228.0721378.195 2.936 Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) N1 2.5 2778.77412.6302293.196 2.737 N1 7.5 2632.91312.6501591.672 2.008 N1 12.5 2977.84413.0441645.657 1.893 N1 17.5 2781.54112.3621558.266 1.818 N1 32.5 2513.40213.5631289.327 1.827 A1 2.5 3073.61814.9321344.809 1.715 A1 7.5 3051.47013.8451681.350 2.003 A1 12.5 2922.95313.6152210.529 2.703 A1 17.5 3226.77815.9081198.267 1.551 A1 32.5 2992.88714.9311227.686 1.608 A1 37.5 3358.44715.6571528.931 1.871 A1 42.5 2985.33615.1811362.495 1.819
204 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Inoceramus candidates Sample [Al] ppm Al/Ca (mMol/Mol) [Ca] ppm I1 2.5 N/AN/A311233.753 I1 7.5 6.7106.710315723.669 I1 12.5 5.9675.967298556.713 I1 17.5 N/AN/A354651.599 I1 22.5 N/AN/A366202.379 I1 27.5 N/AN/A314031.888 I1 32.5 N/AN/A371512.081 I1 37.5 N/AN/A377823.081 I1 42.5 N/AN/A350025.256 I2 2.5 N/AN/A405596.204 I2 7.5 N/AN/A386228.463 I2 12.5 N/AN/A341148.399 I2 17.5 N/AN/A387708.491 I2 22.5 N/AN/A386007.936 I2 27.5 N/AN/A393150.593 I2 32.5 N/AN/A368654.959 I2 37.5 N/AN/A390735.564 I2 42.5 N/AN/A376613.059 I2 47.5 N/AN/A380720.871 I2 52.5 N/AN/A404350.446 I2 57.5 N/AN/A381163.831 I3 N/AN/A352842.797 I3 N/AN/A374635.577 I3 N/AN/A354491.942 I3 N/AN/A356544.725 I3 N/AN/A358457.535 I3 N/AN/A378183.506
205 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Inoceramus candidates Sample [Fe] ppm Fe/Ca (mMol/Mol) [K] ppm K/Ca (mMol/Mol) I1 2.5 740.7841.707280.234 0.923 I1 7.5 6273.96714.255918.821 2.985 I1 12.5 3114.5747.4831159.364 3.983 I1 17.5 372.0690.753260.439 0.753 I1 22.5 728.4801.427209.828 0.588 I1 37.5 1491.2883.407171.881 0.561 I1 32.5 1128.7452.179193.222 0.533 I1 37.5 481.3420.914306.752 0.833 I1 42.5 548.5921.124134.286 0.393 I2 2.5 132.3970.234200.077 0.506 I2 7.5 431.0410.801129.950 0.345 I2 12.5 N/AN/A169.841 0.511 I2 17.5 N/AN/A178.982 0.473 I2 22.5 N/AN/A325.233 0.864 I2 27.5 N/AN/A179.307 0.468 I2 32.5 24.8080.048188.606 0.525 I2 37.5 48.5590.089166.232 0.436 I2 42.5 108.0460.206191.277 0.521 I2 47.5 86.3890.163229.989 0.620 I2 52.5 N/AN/A122.324 0.310 I2 57.5 2366.7744.454253.962 0.683 I3 2.5 17.5470.036168.466 0.490 I3 7.5 341.2050.653194.376 0.532 I3 12.5 193.4550.391523.458 1.514 I3 17.5 1465.7812.949170.131 0.489 I3 22.5 485.4730.972215.001 0.615 I3 27.5 692.3031.313223.124 0.605 I1 2.5 740.7841.707280.234 0.923
206 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Inoceramus candidates Sample [Mg] ppm Mg/Ca (mMol/Mol) [Mn] ppm Mn/Ca (mMol/Mol) I1 2.5 452.4682.399367.301 0.862 I1 7.5 3102.09816.2142778.576 6.428 I1 12.5 902.0694.986410.499 1.004 I1 17.5 124.1780.578133.729 0.275 I1 22.5 441.1421.98865.877 0.131 I1 37.5 401.9732.112258.259 0.601 I1 32.5 81.2420.361154.267 0.303 I1 37.5 99.9080.436N/A N/A I1 42.5 62.3240.294N/A N/A I2 2.5 373.3831.51968.772 0.124 I2 7.5 300.4941.284N/A N/A I2 12.5 204.9980.992N/A N/A I2 17.5 183.9200.783N/A N/A I2 22.5 224.0380.958N/A N/A I2 27.5 153.9880.646N/A N/A I2 32.5 192.4830.8626.257 0.012 I2 37.5 188.4920.796 N/A N/A I2 42.5 283.0731.24040.911 0.079 I2 47.5 272.1511.1804.696 0.009 I2 52.5 221.5440.904 N/A N/A I2 57.5 524.6882.2729.651 0.018 I3 2.5 636.4992.977162.376 0.336 I3 7.5 389.2451.715506.590 0.988 I3 12.5 241.1371.123290.843 0.599 I3 17.5 680.1973.1482131.878 4.367 I3 22.5 1239.6025.707498.207 1.015 I3 27.5 3348.28014.6101256.739 2.427 I1 2.5 636.4992.399162.376 0.862
207 APPENDIX C: MINOR ELEMENTS FOR SCLEROCHRONOLOGY CANDIDATES (CONTINUED) Inoceramus candidates Sample [Na] ppm Na/Ca (mMol/Mol) [Sr] ppm Sr/Ca (mMol/Mol) I1 2.5 3494.36619.5751685.724 2.479 I1 7.5 3106.63517.1551816.394 2.634 I1 12.5 3924.01622.9151787.118 2.740 I1 17.5 4065.83119.9881933.915 2.496 I1 22.5 4246.49820.2172114.187 2.643 I1 37.5 3499.89319.4311632.272 2.379 I1 32.5 4059.59019.0512098.192 2.585 I1 37.5 4337.16420.0142058.813 2.494 I1 42.5 3785.82418.8572102.860 2.750 I2 2.5 4558.48619.5951987.458 2.243 I2 7.5 4213.40419.0202010.075 2.382 I2 12.5 3960.49520.2411660.538 2.228 I2 17.5 4316.05319.4091951.055 2.304 I2 22.5 4343.95219.6201939.585 2.300 I2 27.5 4546.84720.1641959.102 2.281 I2 32.5 4472.34021.1511786.193 2.218 I2 37.5 4511.54520.1312049.885 2.402 I2 42.5 4440.40120.5561794.189 2.181 I2 47.5 4283.95519.6181830.258 2.201 I2 52.5 4288.87118.4931887.894 2.137 I2 57.5 4317.31819.7481713.865 2.058 I3 2.5 3907.01019.3052010.343 2.608 I3 7.5 4882.86122.7242139.548 2.614 I3 12.5 4029.17819.8162077.490 2.683 I3 17.5 3586.00117.5351907.647 2.449 I3 22.5 3842.40718.6892011.537 2.569 I3 27.5 3803.93417.5371818.348 2.201
208 APPENDIX D: STABLE ISOTOPE SCLEROCHRONOLOGY Sample del-13-C del-18-O I2 L05 5.23-5.32 I2 L10 5.72-5.87 I2 L15 5.54-5.55 I2 L20 5.89-5.59 I2 L25 N/AN/A I2 R05 5.63-5.35 I2 R10 5.96-5.77 I2 R15 6.10-5.66 I2 R20 6.02-5.72 I2 R25 4.52-3.62 I2 MTX N/AN/A I2 0 5.47-5.44 I2 2.5 4.59-7.02 I2 5 3.72-7.19 I2 7.5 4.17-3.83 I2 10 5.72-5.43 I2 12.5 5.25-6.55 I2 15 5.96-5.73 I2 17.5 5.94-5.81 I2 20 5.54-5.14 I2 22.5 5.76-5.82 I2 25 5.83-5.60 I2 27.5 5.94-5.73 I2 30 5.89-5.65 I2 32.5 6.10-5.66 I2 35 5.40-5.23 I2 37.5 5.95-5.52 I2 40 3.95-4.18 I2 42.5 5.61-5.57 I2 45 5.92-5.63 I2 47.5 5.84-2.21 I2 50 5.15-5.07 I2 52.5 6.00-5.77 I2 55 6.07-5.55 I2 57.5 5.45-5.53 I2 60 5.64-5.58
209 APPENDIX D: STABLE ISOTOPE SCLEROCHRONOLOGY (CONTINUED) Sample del-13-C del-18-O B7 L2.5 -3.40-1.44 B7 L5.0 N/A N/A B7 L7.5 -2.68-1.06 B7 L10.0 -3.08-1.54 B7 L12.5 -2.51-1.07 B7 R2.5 -2.98-1.35 B7 R5.0 N/A N/A B7 R7.5 -3.17-1.54 B7 R10.0 -5.61-3.47 B7 R12.5 -5.50-1.72 B7 MTX -23.65-2.10 B7 0 -11.8716-1.44463 B7 2.5 -2.95515-1.05585 B7 5 -2.80042-0.96956 B7 7.5 -2.67933-1.12274 B7 10 -5.47786-1.40391 B7 12.5 -2.78312-1.16152 B7 15 -3.74223-1.29338 B7 17.5 -2.91671-1.13923 B7 20 -2.81291-1.25169 B7 22.5 -3.11564-1.43784 B7 25 -3.52696-1.84117
210 APPENDIX D: STABLE ISOTOPE SCLEROCHRONOLOGY (CONTINUED) Sample del-13-C del-18-O E2 L05 N/AN/A E2 L10 1.26-0.34 E2 L25 0.33-0.48 E2 L30 0.03-0.78 E2 R05 0.74-0.81 E2 R10 0.59-0.66 E2 R15 0.40-0.60 E2 R20 -0.66-1.37 E2 R25 -0.20-0.76 E2 MTX -22.15-1.69 E2 CEM1 -14.97-4.03 E2 CEM2 N/AN/A E2 CEM3 0.18-1.18
211 APPENDIX D: STABLE ISOTOPE SCLEROCHRONOLOGY (CONTINUED) Sample del-13-C del-18-O E2 0-2.34-1.99 E2 5-1.57-1.29 E2 10-1.24-1.43 E2 15-1.38-1.47 E2 20-1.04-0.99 E2 25-0.93-1.21 E2 30-0.89-0.84 E2 350.70-0.81 E2 40-2.28-2.46 E2 45-0.48-0.90 E2 50N/AN/A E2 55-4.41-3.78 E2 60-0.83-1.03 E2 65N/AN/A E2 700.12-1.08 E2 75-1.79-2.16 E2 80-0.59-1.02 E2 85-1.28-1.12 E2 900.43-0.57 E2 95-0.15-0.93 E2 95-0.15-0.93 E2 100N/AN/A E2 105-3.24-1.39 E2 110N/AN/A E2 1150.31-0.71 E2 120N/AN/A E2 125-1.96-0.72 E2 130N/AN/A E2 1350.17-0.79 E2 140N/AN/A E2 1450.16-0.81 E2 150N/AN/A E2 1550.59-0.84 E2 1600.51-0.58 E2 1650.89-0.42 E2 170-13.47-3.29 E2 1750.01-1.15