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Ciembronowicz, Katherine T.
The relationship of initial flooding depositional facies to global sea level and climate on the Marion Plateau, NE Australia (ODP Leg 194)
h [electronic resource] /
by Katherine T. Ciembronowicz.
[Tampa, Fla] :
b University of South Florida,
ABSTRACT: The Coral Sea has been the host to a variety of large carbonate platforms over the geologic past and presently hosts the world's largest system of coral reefs, the Great Barrier Reef, stretching more then 2,300 km along Australia's northeast coast. The Marion Plateau, which today is the site of 400 m deep hemipelagic sediment drifts, once supported two large carbonate platforms that were precursors to reef growth on the central and southern Great Barrier Reef. Previous work examining the growth phases, drownings and rejuvenation of these platforms is extensive. The purpose of this research is to examine the factors controlling the earliest sedimentation on the margin and how it influenced early development of the carbonate platforms.One hundred and eighty-three samples were taken from the base of Hole 1195 B, that was drilled during the Ocean Drilling Program's Leg 194. Analyses were performed using x-ray diffraction on the bulk powder and decalcified less than 2um size fraction smear slides. Four distinct sedimentary facies were defined on the basis of mineralogy and constituent grains.The initial marine transgression of the Marion Plateau was not a straightforward one where a shallow-water margin gradually transitioned into a deep-water margin. Instead, sediments record a complex history of unconformities, hardgrounds, and discrete sedimentary units. The initial flooding was complex as a result of its initially shallow depth at a time characterized by several glacio-eustatic sea-level changes. The data indicate that eustasy has been the strongest control on sediment deposition and clay mineral patterns on the Plateau. Falling sea level resulted in periods of increased detrital input and limited soil formation. Also, a decreasing kaolinite trend in the early Miocene, during a rising sea level, indicates that clays forming on land as a result of climate were not transported out onto the plateau.
Thesis (M.S.)--University of South Florida, 2007.
Includes bibliographical references.
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Adviser: Al Hine, Ph.D.
Ocean drilling program.
x Marine Science
t USF Electronic Theses and Dissertations.
The Relationship of Initial Flooding Depositional Facies to Global Sea Level and Climate on The Marion Plateau, NE Australia (ODP Leg 194) by Katherine T. Ciembronowicz A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science College of Marine Science University of South Florida Major Professor: Al Hine, Ph.D. Pamela Hallock-Muller, Ph.D. David J. Mallinson, Ph.D. Date of Approval: March 26, 2007 Keywords: X-ray diffraction, minerology, clay minerals, ocean drilling program, carbonate platforms Copyright 2007, Katherine T. Ciembronowicz
i TABLE OF CONTENTS LIST OF TABLES .............................................................................................................ii LIST OF FIGURES ..........................................................................................................iii ABSTRACT.........................................................................................................................v INTRODUCTION ..............................................................................................................1 REGIONAL GEOLOGIC SETTING..................................................................................5 Regional Tectonic Setting .......................................................................................5 Regional Acoustic Basement...................................................................................7 Subsidence History .................................................................................................7 Stratigraphy of the Marion Plateau .......................................................................10 Stratigraphy of other Coral Sea Plateaus ..............................................................13 ODP Leg 194, Site 1195, Hole B ..........................................................................19 METHODS ...................................................................................................................... 22 X-Ray Diffraction..................................................................................................22 Random Powder Mounts .......................................................................................22 Clay Smear Slides .................................................................................................23 RESULTS ....................................................................................................................... ..28 Unit V ....................................................................................................................28 Unit IV ..................................................................................................................34 Unit IIIB.................................................................................................................40 Mineralogical Trends and Events .........................................................................40 DISCUSSION....................................................................................................................4 6 Unit V The Initial Marine Transgression ...........................................................47 Unit IV The Early Miocene Flooding ................................................................53 Unit IIIB Establishment of a Distal Setting .......................................................61 Early Miocene Climate and Clay Mineral Deposition on the Marion Plateau .....61 CONCLUSIONS................................................................................................................65 REFERENCES .................................................................................................................66 APPENDICES ..................................................................................................................74 Appendix 1: Site 1195 Hole B ODP Barrel Sheets ...............................................74 Appendix 2: Core and Mineral ogical Data from XRD Analysis...........................80
ii LIST OF TABLES Table 1. Summarized stratigraphic evolution of the northeast Australian margin. .......................................................................................16 Table 2. Sedimentary seq uences of Southern Australia summarized from McGowran (1989), McGowran et al., (1992), Li et al., (2003)...............................................................................................18 Table 3. The range and me an percentages of the dominate bulk sample minerals in lithologic uni ts of site 1195 B....................................................31 Table 4. Mean distribution and percentage range of clay minerals in lithologic units of site 1195 B...................................................................... 31 Table 5. The mean per centages of the dominate bulk sample minerals in lithologic units and mineral associations of site 1195 B..........................38 Table 6 Th e mean distribution of clay mi nerals in lithologic units and mineral associations of site 1195 B...............................................................38 Table 7 Su mmary of biostratigraphic and pale oenvironmental interpretation For the lower portion of site 1195 B.............................................................60
iii LIST OF FIGURES Figure 1. Regional Map................................................................................................ ...2 Figure 2. Physi ographic features of the northeast Australian continental margin including oceanic basemen t, depocenters, major faults and the margins plateaus..................................................................................6 Figure 3. Top ography of acoustic basement with ODP Leg 194 core sites...................8 Figure 4. Ov erview map of seismic me gasequences, lithologic unit boundaries, and acoustic basement for Leg 194s northern transect...........................................................................................................11 Figure 5. Location map of ODP Leg 194 sites and two Miocene carbonate platforms with 200 m bathymetric contours................................12 Figure 6. Sout hern transect seismic line lin king sites 1198, 1199, 1196, and 1197. Site 1196 was cored into the SMP...............................................15 Figure 7. Agedepth model for Site 1195.....................................................................21 Figure 8. Photograph of >2 and <2 m orientated smear slides for core section 47x5w10 to 47x5w110......................................................................24 Figure 9. X-Ray diffraction anal ysis tools....................................................................26 Figure 10. XRD scan of air-dried (black) and glycol saturated (green) clay smear slide..............................................................................................27 Figure 11. Lithologic summary for Site 1195 B including recovery, lithologic units, lithology, glauconite layers, interpreted depositional setting and ages.........................................................................29 Figure 12. Bulk powder r esults from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples......................................................................30 Figure 13. Clay mineral results from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples......................................................................32 Figure 14. Site 1195 Hole B Core 55 X, Cored 515.7 521.2 mbsf.............................33
iv Figure 15. Calc ite to detritus ratio from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples......................................................................36 Figure 16. The ratio of clay mineral results from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples......................................................................37 Figure 17. Site 1195 Hole B Core 50X and 51X, Cored 46 7.7 486.9 mbsf................43 Figure 18. Site 1195 Hole B Core 48 X, Cored 448.4 458.0 mbsf.............................44 Figure 19. Site 1195 Hole B Core 49X, Cored 458.0 467.7 mbsf..............................45 Figure 20. Correlation of lithologic units of Site 1195 B with global cycles of sea level change.........................................................................................48 Figure 21. Comp arison of the lowest part of the drilled sedimentary sequences for Sites 119 3, 1196 an d 1198.....................................................50 Figure 22. A sket ched geologic transect representing all the Leg 194 sites..................51 Figure 23. Cont ours of acoustic basement topography based on seismic data. Fine lines equals ~ 20 m. Orange shading represents the area of restricted circulati on and the seaward extent of siliciclastic material during th e initial marine tra nsgression........................52 Figure 24. ODP Le g 194 Site 1195 B lithologic summary for section of the core sampled in this study.............................................................................54 Figure 25. Cont ours of acoustic basement topography based on seismic data. Fine lines equals ~ 20 m. Orange arrows show remobilization of the siliciclastic sediments and blue arrows depict developing currents that may have redistributed these sediments........................................................................................................58
v The Relationship of Initial Flooding Depositional Faci es to Global Sea Level and Climate on the Marion Plateau, NE Australia (ODP Leg 194) Katherine T. Ciembronowicz ABSTRACT The Coral Sea has been the ho st to a variety of large carbonate platforms over the geologic past and presently hosts the worlds la rgest system of coral reefs, the Great Barrier Reef, stretching more then 2,300 km along Australias northeast coast. The Marion Plateau, which today is the site of 400 m de ep hemipelagic sedime nt drifts, once supported two large carbonate platforms that were precursors to reef growth on the central and southern Great Barrier Reef. Previous work examining the growth phases, drownings and rejuvenation of these platforms is extensive. The purpose of this research is to examine the factors controlling the earliest sedimentation on the margin and how it influenced early development of the carbonate platforms. One hundred and eighty-three samples were taken from the base of Hole 1195 B, that was drilled during the Ocean Drilling Pr ograms Leg 194. Analyses were performed using x-ray diffraction on the bulk powder and decalcified less than 2m size fraction smear slides. Four distinct sedimentary facies were defined on the basis of mineralogy and constituent grains. The initial marine transgression of the Marion Plateau was not a straightforward one where a shallow-water margin gradually transitioned into a d eep-water margin. Instead, sediments record a complex histor y of unconformities, har dgrounds, and discrete sedimentary units. The initial flooding was co mplex as a result of its initially shallow depth at a time characterized by several gl acio-eustatic sea-level changes. The data
vi indicate that eustasy has been the strongest control on sediment deposition and clay mineral patterns on the Plateau. Falling sea level resulted in periods of increased detrital input and limited soil formation. Also, a decreasing kaolin ite trend in the early Miocene, during a rising sea level, indicates that clays formi ng on land as a result of climate were not transported out onto the plateau.
1 INTRODUCTION The present northeast Australia n margin hosts the worlds largest coral reef system, the Great Barrier R eef, stretching more the 2,300 km along the coast. In the geologic past, several regional plateaus have also hosted carbonate platforms including the Marion, Queensland, Eastern, and Papuan plateaus (Fig. 1). Further, a 60 million year history of platform development includ ing initiation and demise is recorded in the carbonate platforms of the northeast Australi an margin (Davies et al., 1991a). These carbonate platforms are comparable in size to most platforms known in the geologic record, such as the Blake Plateau, the Bahama platform, and the Cretaceous and Jurassic reef systems of the southeastern USA (Davi es et al., 1991a). The northern continental shelf of Australia comprises the largest Neogene platform where shallow-water limestones have occupied a wide area for mo st of that period (Betzler et al., 1995; Kiessling et al., 2003). The study site of this research, the Ma rion Plateau, supported two large carbonate platforms during the Miocene which were precu rsors to reef growth on the central and southern Great Barrier Reef. The Marion Plateau is well known for the carbonate platforms it has supported in th e geologic past (Mutter and Karner, 1980; Davies et al., 1991a; Pigram et al., 1992; Marsh all et al., 1998), and it conti nues to support limited reef growth today. However, it is now predominantly a 400 m deep terrace influenced by a western boundary current that accumulates larg e hemipelagic sediment drifts (Isern et al., 2002; Obrochta et al., 2003). Extensive research has examined the growth phases, terminations and rejuvenation of these platforms (Mutter and Karner, 1980; Davies et al., 1991a; Marshall et al., 1998; John and Mutti, 2005; Ehrenberg et al., 2006), but little is known about the initial depositional environments of the Marion Plateau. This research examines the factors controlling the earliest sedimentation on the margin and determines how that may
Figure 1. Regional map. Top left shows the loca tion of the study site in relation to the Australian continent. The Coral Sea region is marked with a red box and is expanded below with elevations in meters. Bat hymetry reproduced from the GEBOC (General Bathymetric Chart of the Oceans) one minute gr id. The Marion Plateau is marked with a blue box. Features marked on the bathymetry include MP= Ma rion Plateau, QP = Queensland Plateau, CSB = Coral Sea Basi n, PP = Papuan Plateau, and EP = Eastern Plateau. 2
3 have influenced the earliest de velopment of carbonate platforms. To this date, it is not known if shallow carbonate environments formed during the in itial flooding, if the shallow marine sediments were coastal silicicla stics, or if the flooding was so rapid that the initial record is prima rily one of deepwater pelagic sedimentation. This work examines the depositional stage that existe d prior to the establ ishment of carbonate platforms. Several comparative structural, sedimentological, climatological, and paleontological studies have documented the d ifferent controls on the origin, evolution, and termination of ancient and modern carbona te platforms (Schlage r, 1981; Read, 1985; Bice et al., 1990; Cocozza and Gandin 1990;; Ellis et al., 1990; and Elmi, 1990; Feary et al., 1991; and Davies et al., 1991a ), including the Great Barrie r Reef (Hurst and Surlyk, 1984) and western Coral Sea (Isern et al., 1996). James and Mountjoy (1983) described tectonic setting, sea-level fluctuations, the na ture of the margins sedimentation, and variations in carbonate-produci ng organisms as the most impo rtant factors in carbonate platform evolution. Tectonic setting is a factor in producing cr ustal structures, whic h act as nuclei for carbonate platform growth and also controls the rate of subsidence which influences the amount of carbonate sediment that can accu mulate. The development of carbonate platforms is also strongly c oupled to the rate of biogeni c sediment production. Sudden changes in local or regional environments that affect the carbonate-producing organisms can control platform development (Schlager, 1981). Sea-level fluct uations are important not only for the influence over water depth, i.e., staying within the photic zone, but also for the influence over the flux of terrigenous material reaching the outer shelf. A component of this terrigenous material, the clay minerals, is the result of chemical weathering of rocks associated with climate ch anges, variations in marine circulation, and continental morphology which includes te ctonic activity (Chamley, 1989; Robert and Chamley, 1987). Clay mineralogy is a reliable tool for the study of paleoenvironmental conditions as expressed by the siliciclastic sedimentary fraction (Chamley et al., 1993). Marine clay-mineral characteristics may be used as reliable indicators of successive climates that occurred in a given continental domain, espec ially when supplemented by
4 other indicators (Chamley and Debraban t, 1984; Robert and Chamley, 1987; Chamley, 1989; Curtis, 1990; Robert and Kennett, 1997; Thiry, 2000; Adatte et al., 2002; Mallinson et al., 2003). As described above, there are many factors that can influence the evolution of a margin and the development of carbonate pl atforms. Ocean Drilling Program (ODP) Leg 194 allowed for the examination of deposit ional processes involved in creating and maintaining a mixed carbonate-siliciclastic carbonate platform sy stem. Mineralogical data were used to define the initial flooding of basement on the Marion Plateau, and to identify the associated depositional envir onment and its longevit y. Several specific research questions are addressed in order to define the paleoceanographic and paleoclimate record within these sediments. First, what is the mineralogy and textur al characteristics of sediments directly overlaying basement? Second, which of the factors (tectonics, sea level and variations in carbonate producers) played a major role in th e initial flooding of the Marion Plateau? Is there a linkage between this local transgress ion and the eustatic sea -level changes? Were there significant changes in global sea level during the flood ing stage and how did they affect sedimentation? Finally, does the clim ate signal interpreted from the clay mineral assemblages of the Marion Plateau agree with other climate proxy records derived on land?
5 REGIONAL GEOLOGIC SETTING Regional Tectonic Setting Co ntinental Margin Development The Marion Plateau is one of several continental margin al plateaus in the western Coral Sea that record a complex history of rifting, seafloor spreading, and subsidence. This continental margins major physiographic features include: the Queensland, Townsville, and Cato Troughs, the Eastern, Queensland and Ma rion Plateaus, and the Coral Sea Basin. The physiographic features of the western Coral Sea can be seen in Figure 2. Initial basin forming events, late Jurassic to early Cretaceous in age, are responsible for the Townsville and Queens land Troughs (Struckmeyer and Symonds, 1997). The structural interpretation of the Townsville B asin indicates that it formed part of a complex rift system that utilized Palaeozoic structural trends and is now ch aracterized by a halfgraben morphology bounded by major normal fa ults (Struckmeyer and Symonds, 1997). The formation of both troughs is thought to be independent of later sea-floor spreading events in the Coral Sea and Tasman basins (Struckmeyer and Symonds, 1997). The seafloor spreading episode culminati ng in the Tasman Sea basin formation occurred between 80 and 55 Ma (Hayes and Ring is, 1973; Shaw, 1978). Spreading in the northernmost Tasman Sea may be contemporane ous (i.e., 63.5 Ma) with the openings of the Cato Trough and Coral Sea Basin, however no magnetic anomalies have been identified in the Cato Trough (Shaw, 1978; Mutter a nd Karner, 1980; Struckmeyer and Symonds, 1997). The Coral Sea abyssal plain is underlain by oceanic crust. Seafloor spreading in the Coral Sea Basin commenced in the early Tertiary and has been constrained by magnetic anomaly to 63.5 to 55.5 Ma (Mutter and Karn er, 1980; Struckmeyer and Symonds, 1997; Weissel and Watts, 1979). Normal rifting and breakup of the extended Australia continent associated with this seafloor spreading is th ought to have created the marginal plateaus, therefore the plateau basement is composed of continental crustal material. Post-rift thermal subsidence is believed to be the co ntrolling factor on the long-term accommodation
Figure 2. Physiographic featur es of the northeast Australian continental margin including oceanic basement, depocenters, major faults the Great Barrier Reef and the margins plateaus. The study area, the Marion Plateau, is designated in bold type. (Modified from Davies et al., 1989) 6
7 based on the progression of early shallow-water reef systems to present depths (Isern et al., 2002). Regional Acoustic Basement (ODP Leg 194 Initial Results) Prior to ODP Leg 194 drilling, the Marion and Queensland Plateaus were considered to be underlain by eroded basemen t platforms composed of Early Palaeozoic continental crust rocks of the Tasman Fold Belt (Gardner, 1970; Taylor and Falvey, 1977; Mutter and Karner, 1980; Struckmeyer and Symonds, 1997). A high-resolution multichannel seismic grid consisting of 1,700 km of seismic data was collected in April 1999 and identified the acoustic basement as a hi gh-amplitude reflection at the interface with overlying sediments (~1 sec two-way trave l time) and numerous diffractions caused by the irregular bedrock surface. The basement surface has a slight northeastward dip toward the edge of the plateau, where it is do wn-faulted to the Cato Trough (Fig. 3). Acoustic basement was penetrated at four sites (1193, 1194, 1198 and 1197) during Leg 194, ranging in depth from 420 to 640 mbsf. Altered basalt flows, volcaniclastic breccias, and conglomerates were recovered at those sites. Evidence suggests that these volcanics may have formed during the Late Cretaceous-Paleocene rifting along northeastern Australia from the Papuan Plateau in th e north and the Lord Howe Rise in the south (Isern et al., 2002). Interestingly, these basement rocks differ greatly from those drilled on the Queensland Plat eau where metasedimentary rocks were recovered. Subsidence History Tectonic activity ended after seafloor spr eading in the Coral Sea Basin, and the margin began a thermal subsidence stage. At this post-breakup sag phase (around 55.5 m.y.) a large area of the western Marion Plateau was still emergent, allowing for erosion of the basement surface (Mutter and Karner, 1980). Northeast Australia has not subsided wholly as a result of uniform post-rift thermal c ooling, but through pul ses of subsidence that occurred at different times (Davies et al., 1991a). Initial subsidence is thought to have been very slow or delayed, not commencing immediately following the breakup, and fo llowed by very limited subsidence of all surrounding plateaus in the ea rly Eocene (Taylor and Falv ey, 1977; Mutter and Karner,
Figure 3. Topography of acoustic basement with ODP Leg 194 core s ites. Topography is not depth corrected but represents two-way tra vel time. Fine lines equal ~20 m. The carbonate platforms prevent penetration of the seismic signal. Top left inset shows (blue rectangle) location of basement topogra phy data on the Marion Plateau. (Modified from Isern et al., 2002) 8
9 1980). At this time, deposition was only gradually transgressive, with evidence of clastic aprons around extensive highs on the plateaus (Taylor and Falvey, 197 7). During the late Eocene into the Oligocene, the plateaus of the margin underwent sufficient subsidence to become influenced by ocean currents, and r eefs were established (Taylor and Falvey, 1977; Mutter and Karner, 1980). Deep Sea Drilling Project (DSDP) Site 209 on the Queensland plateau found a lack of pelagic sedimenta tion during this time period, presumed to be caused by deep currents passing across the plateau (Mutter and Karner, 1980). Reef growth seems to have kept up with post-rift subsidence and the slopes of the Marion and Queensland plateaus remained shallow-water en vironments until the late Miocene (Taylor and Falvey, 1977; Katz and Miller, 1993). Ocean Drilling Program Leg 133 drill holes we re used to evaluate the Neogene tectonic subsidence histories of the Marion and Queensland Plateaus using benthic foraminifera (Katz and Miller, 1993) and multip le-analysis data modeling (Mller et al., 2000). Using benthic foraminiferal faunas to estimate paleodepth, Katz and Miller (1993) found three periods of rapid water depth in creases along the northeastern Australian margin occurring during the middle Miocene (~13-14 Ma), late Miocene (6-7 Ma), and late Pliocene (2-3 Ma). Site 815 is located on the northwest edge of the Marion Plateau at the present depth of 465.5 m. Benthic foramin iferal assemblages at a nd below 416.50 mbsf (8.3 Ma) are dominated by reefal and shallow-water taxa and are designated as inner to middle neritic depths, 0 -100m (Katz and Miller, 1993). This site increased in water depth from the outer neritic to upper bathyal zone dur ing the late Miocene (~6.7 Ma). Adjacent to Site 815, Site 816 samples did not supply benthic foraminifers below 91.00 mbsf (lower Pliocene). The middle Miocene depositional env ironment was interpreted to be shallower than 5 m from analyses of floatstones, packst ones and rudstones (Davi es et al., 1991b). Mller et al. (2000) reconstructed the tect onic subsidence history by integrating the geophysical log analysis with biostratigraphi c, lithological, and seismic data. The resulting models, assuming constant eustatic sea level and so a minimum estimate, predict a post 9 Ma subsidence of 660 +/50 m on the northern margin of the Marion Pl ateau. The results of these studies indicate a greater amount of su bsidence than can be predicted from simple
10 elastic models. There is a substantial devi ation from the expected exponential thermal post-rift subsidence of a passive margin (Katz and Miller, 1993; Mller et al., 2000). Recent work (Ehrenberg et al., 2006) evaluating trends in Sr ages for Site 1193 suggests a continuous and relatively slow, 13 m/My, subsidence following transgression. Stratigraphy of the Marion Plateau The Marion Plateau is located between 18 o S and 23 o S, seaward of the south-central Great Barrier Reef on the northeast Australian c ontinental margin. The Marion Plateau is nearly as large as the Blake Plateau in th e western North Atlantic, covering a 77,000 km 2 area. The Plateau is interpreted as a subsid ed continuation of the continental shelf off Queensland. Depths range from 200 m on th e landward margin to 600 m on the seaward with only one large reef on the NW edge. The area is a mixed carbonate-siliciclastic depositional environment with various amount s of terrigenous sedime nt intermixed with platform and pelagic carbonates sediments. The subsidence of the continental margin following the rift-valley stage led to large portions of the continental crust being subm erged while other portions were sub-aerially exposed and eroded. The flooding of these ba sement structures provided large shallow water areas that might have been suitable for carbonate deposition as well as platform development and growth. The first sediments over basement are thought to be primarily siliciclastic, with temperate-water carbonates in the eastern part of the sequence (Isern et al., 2002). Three samples of la rge pristine bivalves collected just above basement in cores 1193, 1197, and 1198 (Figs. 3 a nd 4) were dated us ing Sr-isotope analysis and revealed mean ages of ~ 29 Ma. This places the transgression of th e Marion Plateau in the early Oligocene (Rupelian) (Ehrenberg et al., 2006). High-resolution multichannel seismic data fro m ODPs site survey cruise provided acoustic imagery of middle Oligocene-Holocene sedimentatio n on the Marion Plateau and results were used to identify four unconformity-bound megasequences overlying continental basement. An overview of the characteristics of these seismic megasequences, their lithologic unit boundaries, and the acoustic basement for the northern transect is shown in Figure 4. Recovered sediments from Leg 194 drilling we re used to calibrate the
Figure 5. Location map of ODP Leg 194 sit es and two Miocene carbonate platforms with 200 m bathymetric contour s. Solid black lines are seis mic lines collected during the site survey. Site 1195, used in this study, is marked with a black dot. (Modified from Isern et al., 2002) 12
13 regional seismic stratigraphy by identifying the lithologic signature and providing a chronostratigraphic framework. Seismic data and drilling conducted duri ng Leg 194 (Fig. 5) revealed the Marion Plateau as a largely undeformed basement bl ock supporting two drowned carbonate platforms designated the Northern Marion Platform (NMP) an d Southern Marion Platform (SMP). The two platforms have contrasting biota, architectur e and diagenesis likely related to the degree of platform isolation (Ehrenbe rg and Dickson, 2003). The oldest sediments recovered above basement are Oligocene, wi th deposition of the two large carbonate platforms starting during the early Miocene. The platforms have flat tops and steep-sided geometries similar to tropical faunal assemblages but these consist of cool subtropical assemblages, primarily red algae, bryozoans and la rger benthic foraminifers (Fig. 6). The sedimentary architecture observed for the Marion Plateau carbonate platforms has been attributed to the dominance of bottom current s (Isern et al., 2002). These currents are responsible for the wide low-angle clinoforms found downcurrent of the SMP as seen on the right side of Figure 6. The main growth period for both of the platforms took place in early to Late Miocene and terminated at 10.7 Ma with a final growth stag e seen only in SMP terminating at 6.9 Ma (Ehrenberg et al., 2006). Both platform demise events approximately coincided with falls in global sea level (Ehrenberg et al., 2006). Post drowning, strong bottom currents returned and contribut ed to the development of ha rdground surfaces atop platform sediments (John and Mutti, 2005). The modern seafloor is smoot h with only subtle bathyme tric changes. Hemipelagic drift sediments dominated by pelagic fora minifers have filled all the topographic depressions including the deeper water trough that originally exis ted between the two carbonate platforms. The grainstone texture and dominance of planktonic foraminifers suggest that the sediments of Unit IA, the uppe rmost unit (Fig. 6), were deposited by strong bottom currents in a high-energy hemipelagic setting. The strong influence of currents in the modern environment is demonstrated by the prominent current ripples and surface sediment samples (Iser n et al., 2002).
14 Stratigraphy of other Coral Sea Plateaus Previous investigations of the Queen sland Plateau, Great Barrier Reef and southwestern Papua New Guinea by Mutter an d Karner (1980), Davies et al. (1989), Pigram et al. (1989), Davies et al. (1991 a), and Davies and Peerdeman (1998) have produced data that allow for the description of the depositional history of these plateaus which is summarized in Table 1. At all sites initial sediments consist of siliciclastic detritus changing upsection into carbonate-dominated se diments. An important feature of all carbonate platforms or carbonate-dominated sediment systems in the region was the transition in the Miocene from temperate to tropical climatic conditions, which allowed for rapid rates of carbonate production. This climate transiti on is closely related to the northward migration of the Australian plate, wh ich Davies et al. (1991b) postulated was the principle force in defining th e timing of reef initiation. Falvey and Mutter (1981) outlined the remar kably consistent tectonic style of all five of Australias divergent, passive continen tal margins. Therefore, examination of other Australian margins (e.g. the southern Great Au stralian Bight margin) may offer a valuable corollary to the proposed study area, shedding light on the question of whether other transgressions have similar origins. Southern Australia records four continent-wide transgressions, two in the Late Middle Eocen e and two in the Late Eocene (McGowran, 1989; McGowran et al., 1992; and Li et al., 2 003). Sedimentary sequences of the Southern Australian margin are summarized in Table 2. In the Great Australian Bight Basin, iron-stained quartz sand and glauconitic, bryozoal, neritic sediments were rapidly su cceeded by oceanic carbonates in the middle Eocene (McGowran, 1989). This transgression is part of the continent-wide Wilson Bluff transgression and is equal in age with the Eucla Basin transgression The Saint Vincent Basin offers an example of a stratigraphic sect ion comprising all four transgressions of the margin and records the following history beginning ~ 41 Ma. The lower unit is a nonmarine detrital unit grading upwards into the Tortachilla transgression, consisting of estuarine then neritic carbonate facies topped by a hiatus/hardground. The following Tuketja transgression produced grey-green form ations with a mineralogy dominated by opaline silica, smectite, carbonate and glauconite and lacki ng in kaolinite and detrital quartz. The subsequent units are interpreted to be regressive and incl ude nonmarine detrital
16 Table 1. The stratigraphic evol ution of the northeast Australian margin summarized from these sources: Mutter, J.C. and Ka rner, G.D. (1980), Pigram, C.J., Davies, P.J., Feary, D.A. and Symonds, P.A. (1989), Davies, P.J. McKenzie, J.A., Palmer-Julson, A., et al. (1991a), Davies, P.J., Symonds, P.A., Feary, D.A. and Pigram, C.J. ( 1991b), Davies, P.J. and Pe erdeman, F.M. (1998). Great Barrier Reef Queensland Plateau SW Papua New Guinea Late Cretaceous to Paleocene Emergent plateau Northern shelf was a site of siliciclastic sedimentation. Early Mid Eocene Seas transgressed basement, progressively submerged, some parts of plateau still emergent. First overlain by shallow marine siliciclastic sediments, 50% terrigenous, high energy. Terrigenous detritus decreases from mid to upper Eocene. Passive margin setting. An unconformity separates the middle Eocene to early Oligocene shelf deposits. Late Eocene Calcareous sandstone graded into carbonate mud, deeper water pelagic sediments. Subsidence is slow initially. Mid Eocene to early Oligocene deposition of temperate, shallow-water, carbonate sediments. Late Eocene to Late Oligocene Early Oligocene hiatus at Anchor cay well (north). Erosional Unconformity. ~ 16 m.y at DSDP site 209. Cause: Kennett intensification of bottom currents & Taylor surface currents from west trade wind drift. Subsiding to 600 m during hiatus. Sediments reflect constant gradual (20 m/my) subsidence. Middle Oligocene collision and development of foreland basin. Late Oligocene Pure foraminiferal, nannofossil ooze, mid-bathyal depths. Formation of subtropical to tropical epicontinental sea up to 600 km. Earliest Miocene Temperate siliciclastic sedime nts. Carbonate dominated, 99% carbonate sedimentation. Latest Oligocene to earliest Miocene, carbonate sedimentation reestablished in basin. Oldest deposits consist of red algae-large foram subtropical assemblages. Miocene Transition from temperate to tropical climate conditions in northern GBR. Accelerated subsidence (50 m/my) Subsidence brings plateau below level of significant current influence. Latest Early Miocene Tropical fauna dominate, thick carbonate platform sequence on the central plateau. Extensive tropical, rimmed, carbonate platform up to 500 km across succeeded the subtropical facies. Early Mid Miocene Prolific reef growth throughout northern region. Tropical waters established robust reefal growth. Barrier reefs develop on eastern margin of platform near shelf edge. Large pinnacle reefs develop on structural highs. Late Mid Miocene Declining growth. Falling eustatic sea level.
17 Late Miocene Dramatic diminishing carbonate production with falling eustatic sea level. Global Climate Deterioration. Subsidence increase (40 m/my) till present. Convergence and southward migration of foreland basin. Clastic detritus overfill the proximal foredeep, clastic deposition encroached southward, burying northern part of the carbonate platform. Late Early Pliocene Accelerated subsidence (140 m/ my) Reef growth begins in PlioPleistocene south of Marion Plateau. Overlying quartz sand. Conditions stabilize and carbonate banks rejuvenated on a much reduced scale. Burial of the carbonate platform beneath shallow marine and fluvioclastic sediments. Quaternary Inter-reef areas sediment blanket consists of lower terrigenous (mud-quartz rich; caco3 poor), transgressive faci es and an upper carbonate-rich (less mud; little quartz) stillstand facies. Carbonate sedimentation ceased in the foreland basin but continued on the NE Australian shelf where the GBR was flourishing. Comments: Tropical shelf carbonates facies thinning and age of reef growth younger from north to south. Paleo-climate effects of plate motion. The distribution of carbonateplatform facies in SW PNG reflects the transition from an Eocene passive margin setting to the early stages of foreland basin evolution. Comments: The Queensland and Marion Plateaus platforms ar e precursors to reef grow th on the central and southern Great Barrier Reef. Subs idence produced stepback of the Miocene Marion Plateau carbonate platform to the present position of the Great Barrier Reef shelf. Walthers Law of Succession operates in a lateral as well as a vertical sense as a consequence of the joint effects of northward pl ate motion and subsidence. Process diachroneity is a fundamental factor in platform evolution.
18Table 2. Sedimentary sequences of Southern Australia summ arized from McGowran (1989), McGowran et al. (1992), and Li et al. (2003). Pre-Cenozoic (syn-rift) Fluvial to marginal marine, weat hered ferruginous sands Cretaceous upper Voluminous siliciclastic sediments Tertiary Paleocene Tectonic Dominated phase of sedimentation. Weathered siliciclastic deposition, short term marine ingressions. Sluggish circulation, sea level low but rising Sea Floor spreading between Australia and Antarctica commenced around 55 M a Early Eocene Tectonic-dominated phase of sedimentat i on continues. Siliciclastic sequence interpreted to be fluvial to deltaic in origin. Unconformity Hiatus A lithified s andy surface in nearshore localities by subaerial exposure and weathering. 43 Ma Event* Tectonic dominated sedimentation terminated suddenly. Seafloor spreading, global high SL, warm water influx from Indian Ocean, rapid subsidence. Shift of regional sedimentation from te rri genous regime to carbonate regime. Regional environment established favorable to extensive carbonate deposition, start of carbonate deposition in the western and middle parts of th e margin. Mid to Late Eocene ~ 43 39 Ma Carbonate Ramp Deposition. New paleoceanographic regime triggere d r apid growth of bryozoans and carbonate deposition. Carbonate depos ition delayed 2 5 myr towards the eastern margin where clay-dominated clastics dominated. Sea floor spreading jumps, increased subsi dence, erosion, mass wasting and unconformities. Late Eocene < 39 Ma Slower sea floor spreading, stable high SL, Eocene SL maximum, increas ed silica delivery. Global climate deterioration into th e Oligocene occurs as a success ion of quasi-stable climatic phases bounded by phase changes. Local neritic evidence of a short, sharp, bipolar, transenvironmental Termina l Eocene Event. Early Oligocene Large scale ice buildup on Antarctica. Significant oceanic cooling set in. Mid-Oligocene global unconformity. Mid Miocene Southern margin uplifted, SL dropped be lo w present level. After this shift the present shelf started to develop and receive fine-grain wackstone or clayrich ooze sediment packages. Comments: o All transgressions and corresponding sediment packages are 3rd order level and related to SL fluctuations. The differences in dominant lithology, facies distribution and sediment thickness between basins were influenced by differential subsidence. o (*) The 43 Ma event was inf luenced by the combined effects of tectonics, sudden fall and rise in SL and warm-water influx. The Mid-Eocene carbonate sedimentation change is attributed to global SL and increased temperature.
19 sands, clays and marls. The final Aldinga tra nsgression (~ 37 Ma) was characterized by a restoration of neritic carbonate f acies and a maximum flooding surface. ODP Leg 194, Site 1195, Hole B Figure 5 depicts the bathymetry and loca tion of Leg 194 core sites. Site 1195 is located on the Marion Plateau, approximately 60 km northeast of the south-central Great Barrier Reef margin, at a water depth of 420 m. The site is 70 km east of the early middle Miocene NMP and 60 km north of the Miocene SMP platform. The sediments at Site 1195 record a distal shelf facies with the combin ed effects of changes in platform shedding, detrital input, and pelagic sedimentation, all related to sea level and paleoceanographic changes (Isern et al., 2002). Included in th e main objectives for drilling Site 1195 was to provide insight into the age and sediment ologic response of the postrift drowning of the Marion Plateau. These objectives are addressed in this study. The lithology of Site 1195 is divided into five principal units. Units were numbered according to standard ODP convention from the top downwards. Figure 4 pr esents the lithostratigraphic results for Site 1195. Principal scientific results from Leg 194 revealed the low est part of the sedimentary section (517.5 .7 mbsf), designated unit V (Fig. 4), to be 20 cm of well-cemented skeletal grainstone with coralline algae, larg er benthic foraminifers (LBF), and mollusks. The light yellowish brown limestone contains ab undant LBF. These sediments are overlain or possibly encased by sediments containing be nthic foraminifers and nannofossils that indicate early Miocene deposition. Above unit V, unit IV (467.3 517.5 mbsf) consists of grainstone to sandstone with quartz, ro unded glauconite, carbonate lithoclasts, nannofossils, and broken foraminife rs. The depositional environment is characterized as proximal periplatform in outer neritic water depths based on biotic assemblages and neritic and pelagic components. This unit was de posited during flooding an d initial transgression over acoustic basement. Unit III is also thou ght to have been deposited in a distal periplatform environment at outer neritic to upper bathyal water depths. Unit III sediments contain more organic matter, clay, and quartz with a glauconite rich base (Isern et al., 2002). Site 1195 is an ideal core because of its location on the northeast and seaward edge of the Marion Plateau where the first transgressi ve sediments would have been deposited.
20 Site 1195 also successfully drilled a 517.7 m sed imentary section that includes all seismic reflectors and seismic sequences boundaries, allowing for correlation with other sites. Due to its distal setting and more complete r ecord, Site 1195 was u sed to construct the chronostratigraphy for Leg 1 94. The shipboard age model can be seen in Figure 7. Miocene interval sedimentation rates vary be tween 13 and 67 m/my and are also seen in Figure 7 (Isern et al., 2002). The age model is based on biostratigraphy including both nannofossils and planktonic foraminiferal datums. John and Mutti (2005) presented minor corrections to the ship-board model based on the stable isotope stratigraphy. Timing of the initial depositional events were further refined more recently using strontium-isotope (Srisotope) stratigraphy by Ehrenberg et al. (2006). Site 1195 data were correlated to the other Leg 194 sites using the seismic sequences. Recovery of all sequences at Site 1195, including a middle Oligocene section (Unit V) makes it an excellent core to examine the initial flooding sediments and easily correlate them with other Leg 194 sites. This investigation will analyze the mineral ogy of the bulk rock and clay mineral fraction of ODP Leg 194, Site 1195, Hole B samples. Bulk mineralogy will offer insight into the depositional environment as well as the sediment sources and transport for the plateau. In addition the clay minerals and how they change with the transgression of the plateau will be evaluated. As the terrigenous clays deposited in sed imentary basins result mainly from the surfical erosion of continental soils and ro cky substrates, they may constitute reliable indicators of successive climate conditions on land (Chamley, 1 989). Clay detrital assemblages also reflect the combined influen ces of land petrography and transportation agents (Chamley, 1989; Robert and Chamley, 1987). This marine sediment paleoclimatic information essentially relates to the degree of hydrolysis at the surface of exposed land masses and should be based on relative variations in the a bundance of different clay minerals (Chamley, 1989). This study will ev aluate the abundance of individual clay minerals and also the ratio of these mineral s to each other. The comparison of clay mineralogy with other parameters such as pe rcent carbonate may provide insight into northeast Australias regional climate response to early Oligocene to early Miocene events and will supplement information on sea-level variations.
Figure 7. Age-depth model for Site 1195.Vertical lines are epoc h boundaries labeled at the top of the diagram. Horizontal lines to the age-depth curve are lithologic unit and megasequence boundaries. Note the poor recovery in Unit IV. (Source: Isern et al., 2002) 21
22 METHODS Results discussed here were obtaine d from 182 Ocean Dr illing Program (ODP) samples taken from hole 1195 B. Samples were co llected from the base of the core at 517.7 mbsf to 429.2 mbsf at 20 cm intervals wher e recovery allowed. Analyses were performed using x-ray diffraction techniques on the bul k-powder portion and on smear slides of the decalcified, less than 2m size fraction. X-Ray Diffraction Random powder mounts of the bulk rock The ODP provided plugs of sediment sampl es from Hole 1195 B. These samples were disaggregated using a mortar and pestle to a homogenous powder and pressed into a powder holder to create a randomly oriented powder mount sample. Mineralogical analyses were performed on the College of Marine Science, University of South Floridas Bruker Analy tical X-Ray System, Inc. D4 Endeavor X-Ray diffractometer, XRD. The XRD is housed at th e U.S. Geological Surv ey, St. Petersburg, Florida. Samples were scanned from 2 to 40 degrees 2 with a step increment of 0.02 degrees, a scan speed of 2 sec/st ep, a rotation of 60 and diverg ent and antiscatter slits set to 1. Phyllosilicate content in th e bulk-rock samples was estimate d by using the 19.8 degrees 2 peak, K-feldspars by the 27.5 degrees 2 peak, plagioclase by th e 27.8 27.9 degrees 2 peak, quartz by the 26.6 degrees 2 peak, and calcite by the 29.4 degrees 2 peak. Mineral abundance was evaluated semi-qua ntitatively by determining peak intensities (peak height) of the x-ray diffraction results with DIFFRAC plus EVA V.8.0 software. The peak height above background of the dominant minerals was used with the sum of all peak heights, including those not assigned to a specific mineral to obtain a relative percentage. Thus, bulk-rock data are presented in relative peak height percent.
23 The bulk-rock x-ray diffraction results were used to calculate a calcite to detritus ratio. The ratio is expressed as a percentage. The detrital material identified in the scans includes phyllosilicate, quartz, and feldspars. C/D = Calcite / (quartz + phyllosili cate + K-feldspar + plagioclase) Clay smear slides X-ray diffraction analysis is a basic t ool used to determine the nature and proportions of the clay minerals present and fro m there to make deductions on things like sediment provenance and paleoclimate. Cl ay mineralogy was assessed according to methods outlined in Moore and Reynolds (1997). Final clay mineral XRD analysis was performed on a glycolated smear slide of the decalcified < 2m fraction of the sample. The bulk sample was crushed with a mortar and p estle to a homogeneous powder. Carbonate removal was accomplished by exposing the sample to glacial acetic acid (< 0.3 molar) and rinsing the sample after effervescing stoppe d. A DI rinsing was done by centrifuge method. Next the sediment was re-disper sed in (60 ml) distilled water and sodium metaphosphate was added as a dispersing agent. Centrifuging the sample suspension at 100 0 rpm for 2 minutes 25 seconds isolated the silt-sized fraction based on Stokes law. The < 2m size fraction that remained in suspension was decanted to a beaker. This process was repeated until the supernatant liquid became clear, with a minimum of three separations. The yield or supernatant liquid was then centrifuged at 14,000 rpm for 20 minutes to concentrate the clay fraction. The > 2 m and < 2 m size fractions were then smear ed on a glass slide as a slurry and dried at room temperature to produce a texturally orient ed clay film. Figure 8 shows a typical set of good quality smear slides. Samples were repro cessed from the bulk powder if the clay film cracked, peeled up or was too thi n. Cracks, peels or lumps can bias the angle of diffraction. Smears are also required to be infinitely thick as described in Moore a nd Reynolds (1997). Clay mineral analyses were performed on the same D4 Endeavor x-ray diffractometer. Sample holders capable of running smear slides for the D4 were unavailable, and therefore were custom designed and made for this project. Glass slides
Figure 8. Photograph of >2 and <2 m orientated smears on custom cut glass slides from core section 47 X representing a typica l set of good quality smear slides. were cut to fit the new sample holders dimensions, which allo wed the slides to be rotated during the scan and also archived (Fig. 9). The > 2m, < 2m air-drie d and < 2m glycol-solvated fractions were scanned from 2 to 40 degrees 2 with the same parameter file descr ibed for the bulk-rock analysis. Clay samples on a glass substrate were ethylene glycol solvated in a large desiccator with a few centimeters of glycol in the bottom (kept at room temperature) for 48 hrs directly prior to mineralogical analysis (Figure 9). Exposure to ethylene glycol vapor aids in the detection and characterization of expandable clays. Smectite intensity values were evaluated using the 6.2 degrees 2 peak of only the glycol-solvated oriented clay mount. Figure 10 shows a scan of the smectite peak before and after glycol saturation. The clay constituents of sediment results from the erosion of both soils and rocky substrate, so paleoenvironmental reconstructions were based on the relative variations in the abundance of the different clay miner als identified. Clay mineral abundance was evaluated semi-quantitatively by determining pe ak intensities (peak height) of the x-ray 24
25 diffraction results with both the DIFFRAC plus EVA V.8.0 and the MacDiff (4.2.5) software. The height, after removing background, of selected diffraction pattern peaks were measured to give a relative estimate of the proportions of clay minerals identified in the samples. Hence, the clay mineral data are always reported in relative peak height percentage. The x-ray diffraction peak at 12.3 degrees 2 is the result of the kaolinite 001 peak and a superimposed chlorite 002 peak. In orde r to distinguish these minerals in a mixture, a mathematical profile fitting was applied using the MacDiff software for the K002 (24.9 2 ) and C004 (25.1 2 ) peaks. From the peak fitting resu lts, the relative contributions of the two minerals can be calcu lated. For example, the rela tive percent of kaolinite is calculated by dividing the in tensity of the 24.9 degrees 2 peak by the sum of the 24.9 and 25.2 degrees 2 peaks and multiplying the result by the intensity of the 12.3 degrees 2 peak. The lack of a distinguishable peak at 6.2 degrees 2 indicates that chlorite content was low overall. Kaolinite intensity = 12.3 2 x (K002 / K002 + C004) The peak ratio is a tool for determini ng relative clay mineralogical variations downcore and is most commonly presented as indices of kaolinite/smectite, smectite/illite, kaolinite/illite, and chlorite/illite. Ratios were calculated by dividing the intensities of the 001 hkl peaks for the respective clays. These i ndices were calculated to investigate the variations and trends in mineralogy downcore and also to make this data set easily comparable with other similar work (Robe rt and Chamley, 1987; Ch amley et al., 1993; John et al., 2006). In subsequent text, the ratio s of peak heights of certain clay minerals are presented as K/I for the relative indices of kaol inite to illite. This nomenclature does not describe a mixed layered clay.
Figure 9. X-Ray diffracti on analysis tools. A. Smear slide and puck inside the XRD. Two of the three arms used to rotate the sample hol der during analysis can be seen to the right. B The desiccator chamber used fo r ethylene glycol saturation. C. Two standard powder mount sample holders and one custom made smear slide sample holder for the D-4 Endeavor. 26
Figure 10. XRD scan of air-dried (black) and glycol saturated (green) clay smear slide. Note the shift in position and change in heig ht of the smectite peak for the glycolated sample. Units for the Y axis are counts per second during the scan. 27
28 RESULTS The Leg 194 initial report outlined five major lithologic uni ts for hole 1195 B (Fig. 11). This study investigates the two lower most units, V and IV, as well as the lower portion of unit IIIB. Minerals iden tified through bulk-rock analyses are calcite, quartz, K-feldspar, plagioclase and phyllosilicates (Fig. 12). Calcite and quartz are the dominant minerals with average peak height percentages of 76.8% and 20.7%, respectively. No other carbonate species we re identified. K-feldspar and plagioclase are minor constituents both having average peak height percentages less then 1. The average percentage and range of values for the bul k-rock samples broken down by lithologic unit are shown in Table 3. The dominant clay minerals identified in the clay-sized (<2 m) fraction in order of overall peak height percent are smectites (82.6 %), kaolinite (9%), illite (5%), and chlorite (3%) (Fig. 13). All percentages presented here are the average relative peak height percentages of that mineral for the in terval being examined. Quartz, K-feldspar, plagioclase and zeolite were also identified in the clay-sized fraction. The absolute abundance of zeolite is low and is classifi ed based on XRD scans as a member of the heulandite-clinoptilolite family. The average percentage and range of values for the clay mineral assemblages broken down by lith ologic unit are shown in Table 4. Unit V For this study one sample was collected from unit V, which is middle Oligocene in age and found from 517.7 to 517.5 mbsf. This 20-cm section is heavily disturbed from drilling. Cores are cut into 1.5 m long sections and numbered serially from the top of the core. A core with full recovery will have 7 sections and a core catcher, cc, adding up to ~ 9.8 m. Site 1195 Hole B Core 55X is seen in Figure 14. Each core has a visual description barrel sheet which can be found in Appendix 1.
Figure 11. Lithologic summary for Site 1195 B including recovery, lithologic units, lithology, glauconite layers, interpreted depositional setting and ages. Highlighted area is section sampled for this st udy. (Source: Isern et al., 2002 ) 29
Figure 12. Bulk powder results from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples. Vertical scale on far left is in meters below sea floor. Recovery is marked in black with ga ps in white. Columns for individual minerals are labeled at the top and each has a unique horizontal scale presented in relative peak height percent. Even ts noted include the carbonate minimum CM and the plagioclase event 1 Plg 1. 30
31 Table 3. The range and mean percentages of the dominate bulk sample minerals in lithologic units of site 1195 B. Lithologic Unit (age) Depth (samples) Calcite (range) Quartz (range) Phyllosilicates (range) KFeldspar (range) Plagioclase (range) C/D III B (early Miocene) 429.2 463.3 mbsf (130) 86% (42.8 95.8) 12.3% (3.6 50.3) 1.1% (0 3.1) 0% (0 3.7) 0.2 % (0 2.7) 7.8 IV (early Miocene) 463.3 517.5 mbsf (51) 53.4% (4.7 84.4) 42.2% (14.4 87.9) 0.9% (0 1.9) 0.2% (0 5.2) 2.5 % (0 14.0) 1.7 V (early Oligocene) 517.5 517.7 mbsf (1) 77.8% 20.5% 1.7% 0% 0% 3.5 Table 4. Mean distribution and percentage rang e of clay minerals in lithologic units of site 1195 B. Lithologic Unit (age) Depth (samples) Kaolinite (range) Smectite (range) Illite (range) Chlorite (range) K/S K/I S/I C/I III B (early Miocene) 429.2 463.3 mbsf (130) 8.3 % (3.2 13.9) 84.6 % (75.8 91.8) 4.0 % (1.8 10.2) 3 % (1.2 4.8) 0.10 2.36 24.80 0.84 IV (early Miocene) 463.3 517.5 mbsf (51) 10.8 % (0 21.8) 77 % (43.8 89.6) 8.3 % (0 56.1) 3.8 % (0 7.8) 0.14 2.52 18.70 1.00 V (early Oligocene) 517.5 517.7 mbsf (1) 12.4 % 77.2 % 3.8 % 6.6 % 0.16 3.24 20.23 1.74
Figure 13. Clay mineral results from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples. Vertical scale on the far left is in meters below sea floor. Recovery is marked in black with ga ps in white. Columns for individual minerals are labeled at the top and each has a unique horizontal scale presented in relative peak height percent. The yellow region marks the clay mineral event CME. Trends are outlined with arrows. 32
Figure 14. Site 1195 Hole B Core 55 X, Cored 515.7 521.2 mbsf. Sections are numbered at the top are 1.5 meters long. Core catcher section on the far right is lithologic unit V. Note the light brown yellowish color and increase d consolidation in contrast to the greenish gray of unit IV in sections 1 and 2. Un it V was heavily disturbed during coring. 33
34 Unit V is described as a skeletal grainstone containi ng abundant mollusk fragments, coralline algae and lithoclasts from a neritic e nvironment. The skeletal components are dominantly benthic foraminifers. This poorly so rted consolidated sediment is light brown yellowish and was recovered in the core catcher section seen in Figure 14. The facies was described as neritic in nature. Bulk-Rock Samples Unit V shows calcite and quartz values more similar to unit III B than to IV, averaging 77.8% and 20.5%, respectively. Phyllosilicates display the highest values at 1.7%, and the K-feldspar and plagioclase are both 0%. The calcite to detritus ratio has an intermediate value between the other two units with a value of 3.5. (Fig. 15, Table 3) Clay Minerals The clay mineral assemblage for this unit has the highest kaolinite (12.4%) and chlorite (6.6%) values, lowest illite (3.8%) values and in termediate sm ectite (77.2%) values (Fig. 13). The kaolinite/smectite, kaolinit e/illite, and chlorite/i llite ratios were all the highest of the three units, while the smectit e/illite ratio has an intermediate value (Fig. 16, Table 4). Unit IV For this study, 51 samples were collected from unit IV, which is early Miocene (~ 22.7 Ma at its base) in age and found from 517.5 to 463.3 mbsf. The lowermost part of unit IV shows good recovery to about 506 mbsf then poor recovery up to the firmground section near 465 mbsf (Fig. 11). Two sectio ns of core around 479 mbsf and 469 mbsf had sufficient recovery allo wing for sampling. This unit ov erall is a greenish-gray, wellsorted, fine to medium sand-sized grainstone and quartz siltst one to sandstone with high glauconite content. Sediments are rework ed and well sorted with abundant angular quartz grains.
35 Mineral Associations Based on differences seen in both the bul k-rock and clay mineral data, the sediments from hole 1195 B unit IV can be furt her divided into two distinct mineral associations. Units V and IIIB had similar sedimentary characteristics throughout the respective unit and so did not necessitate further division into mineral associations. Unit IV, however, is best character ized with separate mineral as sociations designated here as A and B. The average values for each of these mineral associations are broken down in for the bulk-rock in Table 5 and for the clay minerals Table 6. Mineral Association B (MA B) Mineral association B (506.35 517.25 mbsf) corresponds to the lower portion of lithologic unit IV. A major gap in recovery, ~25m, separates mineral associations A and B. All of core 54X and most of core 55X encompasses the sediments for MA B. The sediments are fine siltto fine sand-sized and are well sorted. Recrystallized and cemented silt-sized carbonate grains domin ate the sediments. Glauconite and pyrite grains are consistently present with more enriched intervals. Bulk-Rock Samples This unit has relatively elevated calcite content (65.4 %) compared with MA A but is still ten to twenty percent lower than other units in the hole. Also, the phyllosilicates average 0.8 % and the K-feldspar av erage is 0.1% (Table 5). K-feldspar is not identified outside of lithologic unit IV. Plagioclase (1.7 %) is lower than in MA A but much higher than other units in the hol e. The calcite to detritus value is 2.3. Clay Minerals In MA B, illite content has the holes low est mean value (3.4 %). All other clay minerals have intermediate values (Table 6). The kaolinite to illite a nd smectite to illite ratios have the highest values for the hole.
Figure 15. Calcite to detritus ratio fro m XRD analysis of ODP Leg 194 Site 1195 Hole B core samples. Vertical scale on the far left is in meters below sea floor. Recovery is marked in black with gaps in white. CD Min marks the minimum event for the ratio. Trends are outlined by arrows. 36
Figure 16. The ratio of clay mineral r esults from XRD analysis of ODP Leg 194 Site 1195 Hole B core samples. Vertical s cale on the far left is in meters below sea floor. Recovery is marked in blac k with gaps in white. Columns for individual ratios are labeled at the top and each has a unique horizontal scale. Trends are outlined with arrows. Note the steady decreasing trend for K/S. 37
38 Table 5. The mean percentages of the dominat e bulk sample minerals in lithologic units and mineral associations of site 1195 B. Lithologic Unit (age) Mineral Assoc. Depth Calcite Quartz Phyllosilicates KFeldspar Plagioclase C/D III B (early Miocene) 429.2 463.3 mbsf (130) 86% 12.3% 1.1% 0% 0.2 % 7.8 IV (early Miocene) A 468.0 479.5 mbsf 26.8% 65.9% 1.0% 0.4% 4.3 % 0.5 B 506.4 517.2 mbsf 65.4% 31.5% 0.8% 0.1% 1.7% 2.3 V (early Oligocene) 517.45 mbsf 77.8% 20.5% 1.7% 0% 0% 3.5 Table 6. The mean distribution of clay minerals in lithologic units and mineral associations of site 1195 B. Lithologic Unit (age) Mineral Assoc. Depth Kaolinite Smectite Illite Chlorite K/S K/I S/I C/I III B (early Miocene) 429.2 463.3 mbsf 8.3 % 84.6 % 4.0 % 3 % 0.10 2.36 24.80 0.84 IV (early Miocene) A 468.00 479.55 mbsf 10.0 % 69.9 % 18.0 % 2.1 % 0.15 2.11 19.67 0.69 B 506.35 517.25 mbsf 11.3 % 80.6 % 3.4 % 4.7% 0.14 3.49 25.82 1.46 V (early Oligocene) 517.5 517.7 mbsf 12.4 % 77.2 % 3.8 % 6.6 % 0.16 3.24 20.23 1.74
39 Mineral Association A (MA A) Mineral association A (468.00 -479.55 mbsf) corresponds to the upper portion of lithologic unit IV and is the most dissimilar section of Site 1195 B evaluated here. A firmground marks the top of this unit. This unit has the lo west mean calcite content (26.8%) of hole 1195 B. This low calcite hor izon is also associated with glauconitic sandstone. MA A is comprised of cores 50x and 51X, which are both glauconitic sandstone with bioclasts (Fig. 17). A visual descripti on barrel sheet for each core can be found in Appendix 1. A clearly observable color change accompanied the transition into glauconitic sand observed in core 50X. Th e sediments are well-sorted and predominately composed of glauconite and angular quartz. The facies was described as hemipelagic in nature. Bulk-Rock Samples As seen in Table 5 MA A has the highest quartz content of the hole (~ 66%), which is twice the values for MA B and thr ee to six times higher then the remaining portion of the hole examined. Plagioclase values are also the highest of the hole at 4.3 % which is two and a half times greater than in MA B and more than twenty times greater than the remaining portions of the hole. In addition, K-feldspar values are the highest of the hole with relative percents of 0.4 %. The calcite to detritus ratio is extremely low with a value of 0.5. Clay Minerals Separating lithologic unit IV into these two associations amplifies the large increase in illite content for this section (Table 6). MA A has an extremely high illite value (18 %) that is four to six times greater then other sec tions in the hole. Chlorite (2.1 %) and smectite (69.9 %) display the lowest values and kaolinite (10 %) has an intermediate value. The kaolinite to smect ite ratio has an intermediate value while the other three clay ratios (K/I, C/I, S/I) have the lowest values for the hole.
40 Unit IIIB I examined 130 samples from 429.2 to 463.3 mbsf within subunit III B, which is early Miocene in age (~19.6 ma) at its base. A firmground marks the contact between units IV and III B. There is a gap in rec overy of several meters around 447 mbsf, this section overall has 86% core recovery. The base of this subunit is represented by cores 46X to 49X. The top two cores alternate between silt-sized wackstone and siltto very fine sand-sized packstone while the lower two cores alternate between the packstone and fine to medium sand-sized grainstone. The textural change to a skeletal grainstone is associated with a color change from dark greenish grey to light olive grey (Fig. 18). The lowermost section is a light to dark olive gray grainstone with rare quartz grains. The clay content decreases markedly down core to become nearly absent in the core catcher, while glauconitic grains b ecome very abundant down core (Fig. 19). Bulk-Rock Samples Unit III B has the highest percentage of calcite averaging 86%, including the highest value of all samples at 95.8%. This unit also has the lowest average quartz value (12.3%), intermediate phyllosilic ate value (1.1%), and the low est K-feldspar value (0%). A plot of the bulk-rock results down core are presented in Figure 12. The highest calcite to detritus ratio value is found within unit IIIB at 7.8, Fig. 15 and Table 3. Clay Minerals Unit IIIB has the lowest kaolinite (8.3 %), the lowest chlorite (3%), highest smectite (84.6%), and intermedia te illite (4%) values. A plot of the clay mineral results down hole are presented in Figure 13. The kao linite/smectite (K/S), kaolinite/illite (K/I), and chlorite/illite (C/I) ratios were all the lowest out of the three units analyzed, while the smectite/illite ratio (S/I) was the highest (Fig. 16, Table 4) Mineralogical Trend and Events A plot of the bulk-rock results is show n in Figure 12. Calcite and quartz vary inversely for the length of the hole investigated. Calcite has fluctuating values in an
41 intermediate range in MA B, then a decreasing trend to its minimum values (CM in Fig. 12) in MA A. Above the firmground, calcite increases and remains high, averaging 86 %. The plagioclase content fluctuates in MA B and then increases and remains high for all of MA A. This event is noted as Plg1 (Fig. 12). A plot of the calculated calcite to detritu s ratio is shown in Figure 15. Values for this ratio fluctuate in the low range over MA B then decrease to near zero values in MA A. This event is denoted calcite detritu s minimum (CD Min). A bove the firmground and into unit III B, there are th ree discernable trends in th e sediments; an increasing trend (CD1) up to 454 mbsf, then two decreasing trends from 455 to 448.5 mbsf (CD2) and 446 to 439 mbsf (CD3). A plot of clay mineral results is s hown in Figure 13. Smectite, kaolinite and chlorite content show sharp fluctuations in MA B, while illite content stays consistent. In MA A, all clay minerals display their larges t amplitude fluctuations, lowest content, and highest content. This clay mineral event is marked CME (Fig. 13). Kaolinite, chlorite, and illite have their highest content while smectite has its lowest. Above the firmground, illite shows a slight increa sing trend from 463.475 to 455.15 mbsf, then decreases and plateaus around 4% Chlorite content plateaus above the firmground (~ 3.5 %) then show s a decreasing trend from 4 46 to 438 mbsf to about 1.5 %. It then stabilizes around 3 % for the rest of the hole examined here. Directly above the firmground, kaolinite values are high (~13 %), then there is a decreasing trend from 460.5 to 435.75 mbsf (K1). Smectite plateau s just above firmground at ~ 80 % and then shows an increasing trend (S1) from 451 to 438 mbsf. A plot of the calculated clay mineral peak ratios is shown in Figure 16. The K/I, S/I, and C/I ratios show a flu ctuating but overall decreasi ng trend from 512 to 508 mbsf, followed by an increase before a gap in recove ry. The K/S ratio shows an increase just before the recovery gap, and then thr ough MA A has its most extreme variations including the lowest and highest (KS1) va lues of the hole. Directly above the firmground or top of unit IV the K/I, S/I and C/I all show decreasing trends up to 456 mbsf, then a large spike around 454 mbsf, followed by an increasing trend from 453.3 to 448.45 mbsf. Above 445.96, these three indices s how a general decreasing trend to the top of the hole sampled with only slight differences between them. The C/I trend
42 becomes more gradual and the S/I trend displays large fluctuations in values. The K/S ratio increases to 0.18 directly above the firmground, and th en decreases and fluctuates around 0.12 until 450.35 mbsf where a decreasing trend occurs for 14.6 m.
Figure 17. Site 1195 Ho le B Core 50X and 51X, Cored 4 67.7 486.9 mbsf. Sediments are a dark grayish green in sharp contrast to the light olive gray of core 49X. Recovery is much lower in these cores with only 2 of the possible 7 sections retrieved. 43
Figure 18. Site 1195 Ho le B Core 48 X, Cored 448.4 4 58.0 mbsf. Note the excellent recovery with 7 sections over a meter each and the core catcher. 45 cm down in section 3 there is a color change to a light olive gr ey associated with a textural change. 44
Figure 19. Site 1195 Ho le B Core 49X, Cored 458.0 467 .7 mbsf. Note the Darker olive grey of the core catcher (cc). Fine to medi um sand-sized glauconite grains become very abundant downcore and clay content b ecomes nearly absent in the cc. 45
46 DISCUSSION Interpretation of the initial marine transgression of the Marion Plateau, based on bulk-rock samples and clay min eral assemblages, was not a straightforward one where a shallow-water margin gradually transitioned into a deep-water margin. Instead, sediments record a complex history of unconformities, hardgrounds, and discrete sedimentary units. Results indicate that tectonics and eustasy have been the dominant controlling factors during early sedimentation on the plateau and these along with the prevailing climate, created an environment c onducive to platform growth in the early Miocene. Early tectonic influences involved the dela yed or slow subsidence of the margin, which kept water depths within the amplitude of eustatic sea-level fluctuations. Also, tectonics resulted in paleoclimatic chang es associated with a continuous northward motion of the Australian plate throughout the Cenozoic. The initial flooding of the Marion Plateau coincided with la rge fluctuations in eustatic sea level associated with the first glacioeustatic changes of the Cenozoic. Evidence of these changes is seen in the unconformities, hardgrounds, and exposure surfaces of Leg 194 cores. In addition, changes in sea level during the marine flooding had a strong influence over continental erosion and changes in circulation, including the developm ent of strong bottom currents and the distribution of terrigenous sediments. Early Cretaceous rifting and Paleocene seaf loor spreading opened the Coral Sea Basin. After rifting and p rior to marine flooding, the volcanic basement surface was subaerially exposed and eroded, creating irregular topographic features. Initial transgression of the Marion Plateau, based on Sr-isotope analysis of unaltered mollusks shells from just above basement, took place at ~ 29 Ma for Sites 1193, 1197, and 1198 (Ehrenberg et al., 2006). Site 1196 samples from the lowermost core suggest an earlier transgression (30.5 32.0 Ma) at that location.
47 At Site 1195, this transgression resulted in three distinct sediment units, from oldest to youngest; V, IV, and IIIB. Unit V, Oligocene in age, is a well consolidated, skeletal grainstone containing coralline alg ae, mollusk fragments, and larger benthic foraminifers. Unit IV, early Miocene in age, is a well-sorted grainstone and quartz siltstone to sandstone with rounded glaucon ite, carbonate lithoclast s, and angular quartz grains. Unit IIIB, early to early middle Miocen e, shows alternations between very fine sand-sized packstone and fine to medium sandsized grainstone with rare quartz at its base. Overall these units depict a transiti on from a proximal periplatform to a distal periplatform environment. Each unit is di scussed below to examine the assertion that eustatic sea level change was the controlling force in early plateau sediment deposition. Results from bulk-rock samples will be discussed first followed by the clay mineral results. Then a brief comparison will be made of these Site 1195 units and other sites from Leg 194 and when possible, other sit es from the northeast Australian margin. Unit V The Initial Marine Transgression During an early Oligocene sea-level hi ghstand, neritic carbonates were being deposited above basement at Site 1195 but dr illing results indicate that deposition was terminated as a result of a major eustatic s ea-level lowering event (Fig. 20). Unit V is capped by a hardground and erosional surface indicating that the limestone was exposed (Fig. 11). Larger benthic foraminifers in th e limestone were tenta tively assigned a late Eocene age in the initial reports while benthi c foraminifers within the lithified contact and nannofossils in the surrounding sediment i ndicate an early Miocen e age (Isern et al., 2002). This correlation with a major sea-le vel event helps clarify the complex foraminifera assemblage associated w ith the early limestone unit. Further evidence supporting a major sea-leve l lowering event at this time comes from global sea-level curves based on sequence stratigraphy (Vail et al., 1977; Haq et al., 1988) and marine stable isotopes (Miller et al., 1991), which both depict a large magnitude middle Oligocene sea-level lowering event (Fig. 20). The magnitude of this lowering ranges from estimates of 50 90 m by Miller et al. (1987) to 100 m by Schlanger and Silva (1986). In general, all of the basins of fshore of Queensland exhibit a regional unconformity or hiatus in the Oligocene when sea le vels were low and ocean
Figure 20. Correlation of lithologic units of Ho le 1195 B with global cycles of sea-level change. Sea-level curve after Haq et al. (1988) 48
49 currents may have been stronger (Grimes, 1980 ). Although not permanent ice, this event marks one of the first glacioe ustatic sea-level changes of th e Cenozoic (Miller et al., 1991). In this regard, ODP Leg 194 cores of fer valuable ground truthing supporting the geophysical and isotopic evidence for Early Oligocene Early Miocene events. Other Regional Sites Leg 194 drilling revealed varying lithologi es for the lowermost units of the core sites. Carbonate buildups developed imme diately following the abrupt flooding of basement but they were spatially limited. Drilling penetrated basement at four sites, 1193, 1194, 1197, and 1198. Of these four sites, only two locations, Site 1193 and 1198, contain sediments from seismic megasequence A, the oldest megasequence above basement (Figs. 4 and 6). Sediments above basement for Sites 1194 and 1197 belong to the younger megasequence B. The lowest pa rt of the drilled sedimentary sequences at Sites 1195 and 1196 contains units associated wi th the initial transgr ession but the cores did not reach volcanic basement. Of the six sites, only two, 1193 and 1196, ha ve siliciclastic sediments directly overlying basement. Sediments at the b ase of Site 1193, below the Northern Marion Platform, are composed of a siliciclastic estuarine deposit with large benthic foraminifers and large oysters (Fig. 21). Sediments at the base of Site 1196, below the Southern Marion Platform, are composed of phosphatic sand (Fig. 21). In contrast, Sites 1195 and 1198 reveal coarse carbonate deposits direc tly overlying baseme nt. Site 1198s lowermost unit consists of a lithified skeletal floatstone to rudstone dominated by larger benthic foraminifers and large platy-shaped r hodoliths (Fig. 21). The skeletal assemblage is one found at deep euphotic water depths, ~ 50 -100 m, and may have been deposited on the flanks of a carbonate buildup to the northwest (Isern et al., 2002). Like Site 1195, this limestone unit is capped by a hardground exposure surface. These lower-most units make up the sh allow-water inner-shelf sediments of megasequence A which overlies and infills baseme nt irregularities. The irregular initial topography of the basement may have played a direct role in l imiting circulation and controlling the early sediment distribution on the Marion Plateau. In the early stages of flooding, circulation was likely very limited. Fl ooding occurred in basement lows first,
Figure 21. Comparison of the lowest part of the drilled sedimentary sequences for Sites 1193, 1196 and 1198 (from left to right). Si te 1193 contains large oyster shell surrounded by poorly sorted clay-rich sediment Site 1196 contains dark phosphatic sand, and Site 1198 contains a carbona te-rich skeletal floatstone with rhodoliths and larger benthic foraminifers which are orientated horizontally. which left higher areas exposed. These physic al barriers and limite d circulation would produce very different sediment units in diff erent areas on the plateau. For example, Site 1193 is an estuarine sandstone deposit whil e Site 1195 is neritic limestone deposit and these two sites are separated by a basement high or possible paleo-island (Fig. 22). Further upcore, associated with a later sea -level rise, both Sites 1193 and 1195 contain a similar succession of mi xed carbonate and silicic lastic material. Terrigenous sediments may have been confined to the landward areas of higher basement topography (Fig. 23) possibly confined by irregular basement features. The deeper and seaward sites would then have little to no terrigen ous input resulting in a more carbonate-rich deposit. Isern et al. (2002) noted the strik ing absence of terrigenous 50
Figure 23. Contours of acoustic baseme nt topography based on seismic data. Topography presented in two-way travel time (seconds) with fine line contour spaces every 20 ms, which equals ~ 20 m. Orange shading represents the area of inferred restricted circulation and the seaward extent of siliciclastic materi al during the initial marine transgression. Top left in set shows location of basement topography data on the Marion Plateau. Bathymetry modifi ed from Isern et al. (2002). 52
53 components in the unit directly over basement at Site 1194 in sharp contrast to Site 1193s siliciclastic unit which do es lie directly over basement. Site 1194 is in close proximity to Site 1193 (Fig. 5) but situat ed on a basement high supporting the inference of bathymetric control on the initial sediment distribution. Unit IV The Early Miocene Flooding After a late Oligocene hiatus, sediment ation on the margin was reestablished during a subsequent sea-level rise in the early Miocene (Fig. 20) and resulted in deposition of a thick succession of mixed carbonate/siliciclastic material bearing glauconite, Unit IV, and capped by a firmgr ound. The bulk rock and clay mineral assemblages from XRD analysis of this unit i ndicate it is composed of two distinct sediment packages which have been assigned mi neral association B (MA B) and mineral association A (MA A) (Fig. 24). Variations in sea level cause d the mineralogical differences observed in the two sediment packages. Mineral association B was deposited directly above the Unit V hardground surface and is hemipelagic with a mix of carbonate and siliciclastic sediments. The relative proportions of these sediment compone nts show high amplitude variations (Fig. 12). Quartz and plagioclase increase near 512 mbsf and continue to be present in the sediments for all of MA B in varying amounts. These results indicate that terrigenous material was being transported out onto the plateau at this time. The clay minerals smectite, kaolinite, and chlorite also show high amplitude variations in MA-B. Significant transport by bottom currents is indicated by the reworked and well sorted nature of the detrital material. In th e seismic reflection data, current-influenced, sculpted sediment drift units ar e evident (Fig. 4). Other si tes, e.g., 1193, reveal bedform features including bidirectional current rippl es indicating strong current activity. Large fluctuations seen in both the bulk-rock (Fig. 15) and clay mineral (Fig. 17) components likely indicate bottom currents changing directio n and intensity at th e time of deposition. The plateau is deepening with a rising sea level and the developing currents would have to adjust to deeper water and different bat hymetry resulting from the infilling of the basement resulting in shifting currents a nd sites of deposition or erosion.
55 Mineral association A record s a mineralogy uniq ue from the rest of the hole examined for this study. Results show a d ecrease in carbonate mate rial and suggest an increase in physical erosion on the continent with rapid transport and burial of sediments on the plateau. This increase in continental shedding is attributed to falling global sea level (Fig. 20). In the bulk-rock results, large spikes are seen in plagioclase and increased quartz abundance (Fig. 12). Plagioclase minerals be long to the feldspar group and are among the most common rock-forming minerals. K-fe ldspars occur in granite and plagioclase feldspars occur in basalts. This mineral group is among the first to break down when exposed (Leet and Judson, 1965). Since chemic al weathering converts these minerals at a rapid rate, their presence in sedimentary rock s suggests that mechanical weathering is dominant. Quartz and feldspar sedimentary grains are considered characteristically terrigenous, so their increase in the sediments of the plateau suggests an increased contribution from the continent at this time. Additionally, the quartz grains in this section of the core are angular in nature further supporting rapid transport and burial. The uppermost part of MA A includes the lowest ca lcite value of the core, denoted as calcite minimum (CM) on Figure 12. Results also show a calcite to detritus ratio of 0.5, denoted CD Min on Figure 15, which is the lowest value for the core. Low calcite values and high detrital input suggest a lower sea-level stand with increased continental erosion and transport to the marine basin. Sea-level fluctuations during the ea rly Miocene affected clay mineral sedimentation on the Marion Plateau by controll ing the degree of erosion and preventing extensive soil formation. The results show a relationship of high ill ite and high chlorite with low smectite, which suggests low pr ecipitation and cool climate where active mechanical erosion is limiti ng or preventing soil formation. These results are labeled as the clay mineral event, CME in Figure 13. The contemporaneous increase of quartz and feldspars, presented earlier, further suppor ts this type of continental setting. Illite is the byproduct of weathering reactions with low hydrolysis that is typical for cool to temperate and dry climates (Moore and Reynolds, 1997). Limited hydrolytic processes and an increase in direct rock erosion will increase th e relative abundance of illite (Chamley, 1989). Chlorite s primarily originate from crystalline igneous and
56 metamorphic sources preserved from chemical w eathering or from the alteration of some volcanic rocks (Chamley, 1989). Hence, illit e and chlorite are indicative of weak chemical weathering intensities. This can be the result of colder climate, areas of higher relief or both. Increased illite, chlorite, quartz, and feldspar suggest an environment where chemical weathering is replaced by physical weathering and soil erosion is replaced by rock erosion (Singer, 1984). Also in MA A, smectite shows the opposite trend seen with illite and displays lowest values during this clay mineral event. These minerals can form in different chemical e nvironments, mostly surficial soils and sediments. Smectite is often linked to transgressive seas and is abundant in warm climates with alternating humid and arid seasons, especially in areas of poor drainage, whereas sharp increases in smec tite content may record increased volcanic activity (Singer, 1984; Chamley, 1989; Roberts and Chamley, 1987; Thiry, 2000; Adatte, 2002). The results for kaolinite also show higher abundance during the clay mineral event accompanied by large variations. Kaolin ite formation is a product of more intense weathering and is more advanced in the relative stability scale fo r clays. As a result, it is less affected after formation by hydrolyzati on and can accumulate on the continent. Since illite and chlorite also increase at this interval, the major kaolinite increase is most likely associated with an influx of detri tal minerals originating through increased continental erosion and not increased soil forma tion. The kaolinite contribution here is the result of erosion of older kaolinite ric h units. Mallinson et al. (2003) found similar circumstances in the Great Australian Bight. Th e kaolinite to illite ratio (Fig. 16) for MA A is very low. Increased terrigenous flux and low K/I ratios often show a relationship with low sea-level stands (Adatte et al., 2002). Haq et al. (1988) report a type 1 seque nce boundary at 21.0 Ma and Miller et al. (1991) correlated a stable isotope zone Mi 1a to around 21.7 Ma (Fig. 20). Miller et al. (1991) identified oxygen isotope zones by their epoch and numbered them from oldest to youngest, e.g. Mi 3. Oxygen isotope shifts can be correlated on a global scale and reflect phases of Antarctic glaciations, i.e., cooling pha ses and drier climates. In addition to the influence of eustasy, the trend to wards more physical erosion c ould also be influenced by uplift in the region associated with volcanic activity. The Nebo Province, located directly west and inland of the Marion Plateau, expe rienced episodes of active volcanism in the
57 Oligocene to early Miocene (Grimes, 1980; Stephenson et al., 1980). Increased relief enhances physical erosion and decreases are as of soil formation. The Nebo Province is also the only Queensland volcanic provi nce with significant quartz abundance (Stephenson et al., 1980). After the period of increased terrigenous transport to the plateau seen in MA A, Site 1195 records evidence of a decline in sediment deposition and of increased current sweeping, indicating a rising sea level. The r esults show that at ~ 463 mbsf there is a firmground associated with layers of high gl auconite concentration (Fig. 24). Glauconitic layers frequently mark the base of a transgressive sequence or are associated with the condensed section of a maximum flooding surface (Haq et al., 1988; Odin, 1988). Glauconite is an authigenic mineral, a hydrous potassium iron silicate, found in marine sedimentary rocks. Its presence is an indicat or of sediment starvation. Glauconite forms by crystal growth within a substrate and requires the interaction of ions, specifically the cations of seawater, and so accumulation of sediment will prevent its formation. Bottom currents are important du ring glauconite formation because higher velocities prevent sediment deposition a nd also because moving water enhances the addition of ions to the evolving grains and reworks the sediment, thereby increasing the grain contact with seawater (Odin, 1988). This hiatus in sedimentation and current sweeping produced the firmground at the top of Unit IV and marks the transition into Unit IIIB. Carbonate substrates are favorable for ha rboring glauconitization and bioclasts can undergo complete evolution producing dark-green grains (Odin, 1988). A decrease in carbonate sedimentation associated with a rising sea level, coupled with the loss of previously deposited carbonate material to the glauconitiza tion process, resulted in the calcite minimum event seen in Figure 12. This relationship of decreased carbon ate accumulation and increased currents associated with an isotopic event is comp arable to the scenario discussed by John and Mutti (2005) for the Mi3 even t in the middle Miocene over the Northern NMP. The current results agree with John and Mutti (2005) and support the idea that eustasy and its paleoceanographic influence has b een one of the strongest controls on platform evolution on the Marion Plateau.
Figure 25. Contours of acoustic baseme nt topography based on seismic data. Topography presented in two-way travel time wi th fine line contour spaces every 20 ms, which equals ~ 20 m. Orange arrows show re mobilization of the siliciclastic sediments and blue arrows depict developing currents that may have redist ributed these sediments. Top left inset shows locati on of basement topography da ta on the Marion Plateau. Bathymetry modified fr om Isern et al. (2002). 58
59 Other Regional Sites The early Miocene saw a major transgression of shallow seas across the Australian continent as evidenced in the li mestones of the Eucla, Murray, and Otway basins. Around this time the northern Great Barrier Reef underwent a transition from temperate to tropical climate c onditions and, by the latest ea rly Miocene, tropical fauna dominated and produced thick carbonate sequences in three areas of the NE Australian margin (Table 1). All Leg 194 sites, except 1194, have abundant quartz sand in the basal interval associated with this flooding event. The quartz abundance then begins to decrease upcore, especially in the southern transect where the southern Marion carbonate platform begins to develop. During re-submergence of the inner shelf area siliciclastic sediments were probably reworked initially and disper sed over the plateau by developing currents (Fig. 26). A continuing sea-level rise pr oduced a deepening-upward trend in a hemipelagic setting for sites 1194 and 1198. S ite 1197 is located dow n-current from the SMP and began receiving skeletal detritus from the neritic platform environment at this time. Both Marion Plateau carbonate build-ups are attributed exclusively to the Miocene but the southern Marion platform appe ars to have started earlier and also had a final growth phase not seen on the Northern Marion Platform. The extended period of growth for the SMP could be attributed to its more isolated character. The NMP is described as a ramp attached to the continent and the SMP as an isolated bank (Isern et al., 2002) with contrasting biota and architecture (Ehrenberg et al., 2006). The fact that the NMP was bryozoan dominated while the SM P was coralline algal dominated could be the result of higher turbidity associated with greater terrigenous inputs at the NMP. In the early stages, when sea level and shelf width were changing and currents were adjusting, the NMP was probably more heavil y influenced by detrita l material preventing initiation.
61 Unit IIIB Establishment of a Distal Depositional Setting Unit IIIB was deposited above the firmground and indicates a continued transgression of the plateau which resulted in a distal depositional setting. Results show increasing calcite (Fig, 12), decreasing detri tal input (Fig. 15), a change in depositional texture (Fig. 24) and a change in the forami niferal assemblage (Table 7) all supporting an increase in water depth over the plateau. Calcite increases abruptly at the base of unit IIIB near 463 mbsf and values remain high (around 86 relative percent) with on ly low amplitude variations. Quartz and plagioclase shows the opposite with a sharp decrease in values. Together these mineral changes indicate a more distal detrital source. Starting at 463 mbsf, the average calcite to detritus ratio is the highest of the hole, 7.8 (Table 3, Fig. 15). This high value may re sult from diminished detrital input from the continent, dilution from an increase in carbonate sedimentation, or variations in carbonate dissolution. Three trends have been identifie d in C/D ratio for unit IIIB, denoted CD1, 2 and 3 in Figure 15. Directly above the firmground, the C/D ratio shows a steadily increasing trend followed by two excursions with peak C/D values at ~ 455 and ~443 mbsf. CD 1 reflects the diminished terrigenous input, the return of pelagic carbonates and initially neritic input wh en sea level is rising. Depositional texture also changes with the onset of unit IIIB. Older sediments were classified as a grainstone which lacks mud and is grain supported but now the Unit IIIB sediments are classified as a wackestone to mudstone which contains more clay and fine silt-sized material (Fig. 24). This change suggests a lower energy environment and deeper water where the clay size fraction coul d settle out and become part of the matrix. Changes in foraminiferal assemblages also support an increase in water depth during deposition of this unit. Tabl e 8 indicates that a neritic shallow water benthic assemblage transitioning into a deep-water dominated assemblage with more planktonics and fewer larger benthic foraminifers.
62 Early Miocene Climate and Clay Mi neral Deposition on the Marion Plateau The clay mineral data in Unit IIIB do not exhibit large excursions in values but, like the bulk-rock component, now only show low amplitude variations with long term trends (Fig. 13). The results for Unit IIB show steady but opposite trends for the two dominant clay minerals. Kaolinite steadil y decreases (K1) while smectite (S1) has an overall increasing trend (Fig.13). Kaolinite is the byproduct of highly hydrolytic weathering reactions in warm humid climates. Kaolinite abundance express es a strong climatic dependence controlled by the intensity of continental hydrolysis (Chamley, 1989). This clay mineral characterizes weathering processes in well-drained continental areas and develops when increased leaching by running waters favors hydro lysis of the parent rocks. The alkalineearth elements are removed by the water and the residual silica and aluminum contribute to the kaolinite formation process (Millot, 1970). Increasing kaolinite would entail intensified humidity on the adjacent continen t and high amounts of precipitation. Once formed, kaolinite remains stable in the land scape even if the climate turns drier (Thiry, 2000). The overall trend of decreasing kaolinite to the benefit of smectite seen in the K/S ratio of Unit IIIB (Fig. 16) implies increased aridity because the reduced drainage of continental areas will favor an environment wh ich concentrates chemical elements in the soil, a requirement for smectite formation (C hamley et al., 1993; Adatte et al., 2002). As the terrigenous clays deposited in sedime ntary basins result mainly from the surficial erosion of continental soils and rocky substrates, they may constitute reliable indicators of successive climate conditions on land (Chamley, 1989). This marine sediment paleoclimatic information essentially re lates to the degree of hydrolysis at the surface of exposed land masses and should be re flected in the relative variations in the abundance of different clay minerals (Chamley, 1989). An evaluation of climate based solely on the clay mineral results here suggests a decrease in continental rainfall and esta blishment of seasonally dry conditions in Queensland. If a marked seasonal dry period was established during the early Miocene encouraging smectite formation, then continen tal proxies should also show evidence of decreasing humidity in Queensland. Howeve r, studies using paleobotany (Martin, 1998),
63 continental weathering (Li and Vasconcelos, 2002) and Deep Sea Drilling Project cores (Stein and Robert, 1983) indicate that an incr ease in the continental aridity of Australia did not establish until the mi ddle Miocene and that the ea rly Miocene was a time of relatively high humidity year round supporting rain-forest growth. For example, Li and Vasconcelos (2002) used 40 Ar/ 39 Ar geochronology of supergene K-Mn oxides and mineralogical textur es to evaluate continental weathering in central Queensland, Australia. Throughout a large part of the Cenozoic, alternating wet, weathering-prone conditions, and dry, erosionprone conditions are indicated by the Mn oxide precipitation record preserved at Mt. Tabor. The data indicate that warm and humid paleoclimatic conditions favorable to intense chemical weathering prevailed in central Queensland from late Oligocene to middle Miocene. Extremely intense weathering is indicated for the entire ea rly Miocene between 23 and 15 Ma, which suggests warm and wet climatic conditions. In addition to climate evolution, clay mineral assemblages also reflect the structural evolution of the margin including continental morphology and tectonic activity. Examination of ancient sediments has att ributed low kaolinite values in climates favorable for kaolinite forma tion to the continental mor phology (Chamley, 1979; Singer, 1984). In this scenario, high-kaolinite soils fo rm in more remote, high-relief internal areas that are not yet connected to a conti nuous drainage system to the shelf. Our results indicate that the northeast Aus tralian margin is an area where the clays forming on land as a result of climate change are not being transported and buried in the marine sediments of the plateau near the time of formation but are deposited in shallow inland basins. Grimes (1980) describes kao linite-rich formations west of the Marion Plateau (e.g., the Suttor Formation and Duarrin ga Basin), which are good candidate areas for deposition at this time. These older depos its were also discussed by John et al. (2006) as a possible source area for clay minerals reworked in the middle Miocene when climates were not favorable for kaolinite formation. Strong currents running over the plateau is a second plausible contributing factor for the decreasing kaolinite. Strong currents would carry away the detrital mate rial preventing deposition on the plateau. Therefore, NE Australia is a region where the kaolinite content of shelf sediments can not be used as an indicator of mo re tropical conditions on land.
64 During this transgressive situation, when the majority of te rrigenous material is being trapped in the coastal region, our data show increasing smectite. There are several possible explanations for this. First is grai n size. Smectite consists of fine particles, easily carried farther from the source while kao linite, illite, and chlorite are coarser clay particles and tend to get trapped in neritic environments (Adatte et al., 2002). Second, while kaolinite, illite and chlorite are exclusively inherited minerals, smectite contribution can come from inheritan ce and/or authigenesis. Where there is a recognizable volcanic contribution to the sed iments, glass and volcanic minerals can undergo rapid alteration producing smectite and zeolites. The zeolite Heulandite was detected in the clay sized fraction of the core but only above ~ 444 mbsf in Unit IIIB. This indicates that at least a portion of the accumulated smectite could be associated with a volcanic origin includi ng airborne particles. Bulk-rock and clay mineral data from this study show that the marine transgression of the Marion Plateau was comple x as a result of its initially shallow depth at a time characterized by several glacio-eus tatic sea-level changes and that kaolinite in the sediments of the plateau do not reflect the onset of tropical conditions on land that resulted from the northward plate movement.
65 CONCLUSIONS 1. Eustatic sea level change was the dominan t factor controlling sediment deposition and clay mineral assemblages during the marine flooding. The first depositional environments of the plateau did not persist but were significantly impacted by sea level changes. Falling sea level resulted in periods of increased detrital i nput and limited soil formation. Higher sea level trapped detrital materia l in the near shore which allowed carbonates to dominate out on the plateau. 2. Carbonate sedimentation began to domin ate a previously transitional and mixed carbonate / siliciclastic system ~ 19 Ma during a period of rising sea level. 3. Clay forming on land as a result of clima te change are not being transported and buried in the marine sediments of the plateau near the time of formation but are likely deposited in shallow inland basins. The Marion plateau is a region where th e clay mineral assemblage of marine sediments can not be used to accurately record changes in climate on the adjacent continent. The clay mineral assemblage on the Queensland margin does not reflect the early Miocene establishment of a tropical climate seen in other continental climate proxies. An early Miocene decrease in kaolinite at the expense of smectite did not correlate with the onset of drier conditions in NE Australia.
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74 APPENDIX 1 CORE BARREL SHEETS FOR SITE 1195 HOLE B
81 APPENDIX 2 CORE AND MINERALOGICAL DATA FROM XRD ANAYSIS
Sample Information Sample_IDLegSiteHoleCoreTy peSectioninterval (cm)mbsf 11941195B55X230 31517.45 21941195B55X210.0 11.0517.25 31941195B55X1115 116516.85 41941195B55X195 96516.65 51941195B55X175 76516.45 61941195B55X155 56516.25 71941195B55X125 26515.95 81941195B55X15.0 6.0515.75 91941195B54Xcc5.0 6.0512.75 101941195B54X535 36512.55 111941195B54X510.0 11.0512.30 121941195B54X4145 146512.15 131941195B54X4125 126511.95 141941195B54X4105 106511.75 151941195B54X485 86511.55 161941195B54X465 66511.35 171941195B54X445 46511.15 181941195B54X425 26510.95 191941195B54X45.0 6.0510.75 201941195B54X3115 116510.35 211941195B54X390 91510.10 221941195B54X365 66509.85 231941195B54X340 41509.60 241941195B54X320 21509.40 251941195B54X2145 146509.15 261941195B54X2125 126508.95 271941195B54X2100 101508.70 281941195B54X280 81508.50 291941195B54X260 61508.30 301941195B54X235 36508.05 311941195B54X25.0 6.0507.75 321941195B54X190 91507.10 331941195B54X165 66506.85 341941195B54X135 36506.55 351941195B54X115 16506.35 361941195B52X180 81487.70 371941195B51X275 76479.55 381941195B51X255 56479.35 391941195B51X235 36479.15 401941195B51X215 16478.95 411941195B51X1132.5 135.5478.625 421941195B51X1112.5 113.5478.425 431941195B51X190 91478.20 441941195B51X170 71478.00 451941195B51X140 41477.70 461941195B50X245 46469.35 82
Sample_IDLegSiteHoleCoreTypeSectioninterval (cm)mbsf 471941195B50X2 30 31469.20 481941195B50X1 95 96468.65 491941195B50X1 75 76468.45 501941195B50X1 55 56468.25 511941195B50X130 31 468.00 521941195B49Xcc15 16463.475 531941195B49X4 75 76463.25 541941195B49X4 55 56463.05 551941195B49X4 30 31462.80 561941195B49X3145 146462.45 571941195B49X3125 126462.25 581941195B49X3105 106462.05 591941195B49X3 60 61461.60 601941195B49X3 25 26461.25 611941195B49X2130 131460.80 621941195B49X2105 106460.55 631941195B49X2 80 81460.30 641941195B49X2 50 51460.00 651941195B49X2 30 31459.80 661941195B49X1145 146459.45 671941195B49X1125 126459.25 681941195B49X1 95 96458.95 691941195B49X1 60 61458.60 701941195B49X1 35 36458.35 711941195B49X110.0 11.0458.10 721941195B48Xcc10.0 11.0457.80 731941195B48X710.0 11.0457.50 741941195B48X6130 131457.20 751941195B48X6 75 76456.65 761941195B48X6 50 51456.40 771941195B48X5130 131455.70 781941195B48X5100 101455.40 791941195B48X5 75 76455.15 801941195B48X5 50 51454.90 811941195B48X4115 116454.05 821941195B48X4 95 96453.85 831941195B48X4 75 76453.65 841941195B48X4 55 56453.45 851941195B48X4 30 31453.20 861941195B48X410.0 11.0453.00 871941195B48X3135 136452.75 881941195B48X3110 111452.50 891941195B48X3 85 86452.25 901941195B48X3 65 66452.05 83
Sample_IDLegSiteHoleCoreTypeSectioninterval (cm)mbsf 911941195B48X3 45 46451.85 921941195B48X3 25 26451.65 931941195B48X3 5.0 -6.0451.45 941941195B48X2140 141451.30 951941195B48X2122.5 123.5451.125 961941195B48X2115 116451.05 971941195B48X2 95 96450.85 981941195B48X2 70 71450.60 991941195B48X2 45 46450.35 1001941195B48X2 25 26450.15 1011941195B48X2 5.0 -6.0449.95 1021941195B48X1135 137449.75 1031941195B48X1115 116449.55 1041941195B48X1 90 91449.30 1051941195B48X1 70 71449.10 1061941195B48X1 45 46448.85 1071941195B48X1 25 26448.65 1081941195B48X15.0 6.0448.45 1091941195B47Xcc 20 21445.95 1101941195B47X5110 111445.65 1111941195B47X5 90 91445.45 1121941195B47X5 70 71445.25 1131941195B47X5 50 51445.05 1141941195B47X5 30 31444.85 1151941195B47X510.0 -11.0444.65 1161941195B47X4140 141444.45 1171941195B47X4120 121444.25 1181941195B47X4100 101444.05 1191941195B47X4 70 71443.75 1201941195B47X4 50 51443.55 1211941195B47X4 30 31443.35 1221941195B47X410.0 -11.0443.15 1231941195B47X3110 111442.85 1241941195B47X3 90 91442.65 1251941195B47X3 70 71442.45 1261941195B47X3 50 51442.25 1271941195B47X3 30 31442.05 1281941195B47X310.0 -11.0441.85 1291941195B47X2135 136441.65 1301941195B47X2115 116441.45 1311941195B47X2 95 96441.25 1321941195B47X2 75 -76441.05 1331941195B47X2 55 56440.85 1341941195B47X2 35 -36440.65 1351941195B47X2 15 16440.45 1361941195B47X1125 126440.05 84
Sample_IDLegSiteHoleCoreTypeSectioninterval (cm)mbsf 1371941195B47X1100 101439.80 1381941195B47X180 81439.60 1391941195B47X160 61439.40 1401941195B47X135 36439.15 1411941195B47X110.0 11.0438.90 1421941195B46Xcc30 31437.80 1431941195B46Xcc10.0 11.0437.60 1441941195B46X6110 111437.40 1451941195B46X690 91437.20 1461941195B46X670 71437.00 1471941195B46X650 51436.80 1481941195B46X630 31436.60 1491941195B46X610.0 -11.0436.40 1501941195B46X5115 116435.95 1511941195B46X595 96435.75 1521941195B46X575 76435.55 1531941195B46X555 56435.35 1541941195B46X530 31435.10 1551941195B46X510.0 -11.0434.90 1561941195B46X4130 131434.60 1571941195B46X4110 111434.40 1581941195B46X490 -91434.20 1591941195B46X470 71434.00 1601941195B46X450 51433.80 1611941195B46X430 31433.60 1621941195B46X410.0 -11.0433.40 1631941195B46X3130 131433.10 1641941195B46X3110 111432.90 1651941195B46X390 -91432.70 1661941195B46X370 71432.50 1671941195B46X350 51432.30 1681941195B46X330 31432.10 1691941195B46X310.0 -11.0431.90 1701941195B46X2130 131431.60 1711941195B46X2110 111431.40 1721941195B46X290 -91431.20 1731941195B46X270 71431.00 1741941195B46X250 51430.80 1751941195B46X230 31430.60 1761941195B46X210.0 -11.0430.40 1771941195B46X1110 111430.20 1781941195B46X190 -91430.00 1791941195B46X170 71429.80 1801941195B46X150 51429.60 1811941195B46X130 31429.40 1821941195B46X110.0 11.0 429.20 85
Bulk-Rock XRD Values Sample_IDQuartzCalcite Phyllosilicate (19.8) 22.022.4 23.5 27.5 (KFeld ) 27.8 27.9 ( Pla g io ) 34.9other 14981887420 2378197029.20 3350186134.70 4407209030.30 5372196233.80 6371218031.90 7670180340.90 58 8657187338.10 34.2 33.4 9888188100 93.5 0 101642144300 94.6 111878137233.60 234 121854139331.50 70.6 97.5 131603131739.40 174 14613154034.70 217 15613157343.80 57.2 16808169200 31.1 17782192600 18479107000 19803137625.60 50.2 201073157723.50 30.5 2111241787390 93.5 22964170432.10 27.7 23658231925.70 24562215324.70 251004221622.30 30.1 26868198900 50.7 27862208431.20 130 281032185523.50 111 29976161841.10 52.1 0 301953178000 40.7 31705221800 83 32773212100 30.2 33804196300 29.6 341222144530.80 41 28 35915152436.40 207 36797208000 109 372236128927.30 40.3 382420104032.80 357 392214114900 81.2 401682124026.40 172114 49.9 41176194129.3031 148 33.7 42155510963462.6 101 48.1 43235376135.20 112 441686137540.258.9 514 45232454844.445.6 200 60.2 86
Sample_IDQuartzCalcite Phyllosilicate (19.8)22.0-22.4 23.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 46372420074.1118 89.5 29 474722709530 37.6 48339157741.333.766.5 206 49251251561.800065.2075.4 50377565133.90 554 36.5 51307349141.60 36.3 52515185720.900000103.9 53579184528.20 54385178740.3 86 52.6 551243171335.2 25.9 56296192627.1 57199178222.7 58421213015 59156202624.8 60447224223.4 35.5 49.9 61532212728.9 27.6 18.2 62375218622.6 6325923150 6431922770 27.1 6529323210 66326207026.921.4 6732022502434.6 20.6 68193237117.1 74.8 69202233620.834.7 7021722460 7126222510 72333220629 73202248517.7 7420221420 000 75184217718.6 18.2 7620423340 77161216222 21 7813422340 15.5 79218218619.4 8015821680 81365210229.5 82432208827.5 48.8 83227213923.4 84366245321.3 85290229629.8 8630922350 8731425080 28 88366206934.522.1 89479208023 38.7 90211210922.1 87
Sample_IDQuartzCalcite Phyllosilicate (19.8)22.0-22.4 23.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 91324230422.2 92503189134.8 20.8 93272207839 94251203738.4 95330196039.7 96374192534.6 97287227625.4 98251228322.8 19.9 99620189452.8 31.1 100709209041.2 45.3 101287220832 102359235234 103263227936.9 104353205534.8 105364210148.1 106768157677.1 31.1 107284230037.4 19.5 108860163656.4 41.728.1 109304225436.9 110247230632.1 18.9 111206220930.6 18.8 112383212535.2 113167223520 114198213739.6 115322211243.9 116471186154.5 27.9 117229253824.3 63.2 118262228725 119323236728.8 120433215239.8 121352225838.5 20.7 12217924890 123267229226.7 63.8 124287243330.7 19.5 125237228430.3 126269239435.7 19.7 127362193538.3 28 128278203039.7 20.8 129245237729.3 18.2 130237232833.8 131300221828 132290226041.8 133404206046.4 24.7 134267223122.6 135448229445.9 88
Sample_IDQuartzCalcite Phyllosilicate (19.8)22.0-22.4 23.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 136282223732 40.6 137564195239.7 26.3 138541194546.1 30.822.8 139413190551.2 140502181549.2 62.2 141202249318.5 14219123990 143250260125000000 1441064134763.7 32.7 1451382117574.6 7439.4 146237231329.5 147138253223 148180239436.420.8 149244237324.6 15032422740 151164258527.5 152245201940.2 153243225532.6 154223230039.6 155247229034.7 156284229135 157248226936.8 20.5 158222255327.7000000 159220226928.8 23.1 160256221538.6 161254214437.8 162239243437.825.6 163231228532.722 164181232132.719.4 16598.1264218.4 166285215547.8 167209228729.624.8 168243244028.825.5 16915125740 170141256725.3 171228224444.6 172226231928.2 173187250228.723.718.5 174182245730.822.9 175195250924.718.4 176192252620.819.3 177268230539.1 19.2 178248226029 179244233747.420.9 113 180235226427.4 181193239131.118.5 182198257835.6 18.8 89
Bulk-Rock Relative Percents Sample_IDQuartz Calcite Phyllo 22.0-22.423.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 120.5277.751.730.000.000.000.000.000.00 215.9082.871.230.000.000.000.000.000.00 315.5982.871.550.000.000.000.000.000.00 416.1082.701.200.000.000.000.000.000.00 515.7182.861.430.000.000.000.000.000.00 614.3684.401.240.000.000.000.000.000.00 726.0570.101.590.000.000.002.260.000.00 824.9371.061.450.000.000.001.300.001.27 931.0265.710.000.000.000.003.270.000.00 1051.6445.380.000.000.000.002.980.000.00 1153.3939.000.960.000.000.006.650.000.00 1253.7940.420.910.000.000.002.050.002.83 1351.1642.031.260.000.000.005.550.000.00 1425.4964.041.440.000.000.000.000.009.02 1526.8068.781.920.000.000.002.500.000.00 1631.9266.850.000.000.000.001.230.000.00 1728.8871.120.000.000.000.000.000.000.00 1830.9269.080.000.000.000.000.000.000.00 1935.6161.031.140.000.000.002.230.000.00 2039.6858.320.870.000.000.001.130.000.00 2136.9358.721.280.000.000.003.070.000.00 2235.3462.471.180.000.000.001.020.000.00 2321.9177.230.860.000.000.000.000.000.00 2420.5178.590.900.000.000.000.000.000.00 2530.6867.720.680.000.000.000.920.000.00 2629.8568.400.000.000.000.001.740.000.00 2727.7467.071.000.000.000.004.180.000.00 2834.1661.390.780.000.003.670.000.000.00 2936.3260.211.530.000.000.001.940.000.00 3051.7547.170.000.000.000.000.000.001.08 3123.4573.790.000.000.000.002.760.000.00 3226.4372.530.000.000.000.001.030.000.00 3328.7570.190.000.000.000.001.060.000.00 3444.1752.231.110.000.000.001.480.001.01 3534.1156.811.360.000.000.007.720.000.00 3626.6969.660.000.000.000.003.650.000.00 3762.2435.880.760.000.001.120.000.000.00 3862.8627.010.850.000.000.009.270.000.00 3964.2833.360.000.000.000.002.360.000.00 4051.2137.760.800.000.005.243.470.001.52 4159.8231.961.000.001.050.005.030.001.14 4253.6837.841.172.160.000.003.490.001.66 4372.1523.331.080.000.000.003.430.000.00 4445.8937.421.091.600.000.0013.990.000.00 4572.1217.011.381.420.000.006.210.001.87 90
Sample_IDQuartz Calcite Phyllo 22.0-22.423.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 4687.944.721.752.790.000.002.110.000.68 4785.5212.840.960.000.000.000.000.000.68 4878.5813.370.960.781.540.004.770.000.00 4977.7915.951.910.000.000.002.020.002.33 5074.7512.890.670.000.000.0010.970.000.72 5184.3813.481.140.000.000.001.000.000.00 5220.6374.380.840.000.000.000.000.004.16 5323.6175.241.150.000.000.000.000.000.00 5416.3876.011.710.000.003.660.000.002.24 5541.2056.781.170.000.000.000.000.000.86 5613.1685.631.200.000.000.000.000.000.00 579.9388.941.130.000.000.000.000.000.00 5816.4183.010.580.000.000.000.000.000.00 597.0791.811.120.000.000.000.000.000.00 6015.9880.130.840.000.000.001.270.001.78 6119.4677.811.060.001.010.000.000.000.67 6214.5184.610.870.000.000.000.000.000.00 6310.0689.940.000.000.000.000.000.000.00 6412.1686.810.000.000.000.001.030.000.00 6511.2188.790.000.000.000.000.000.000.00 6613.3484.691.100.880.000.000.000.000.00 6712.0884.930.911.310.000.000.780.000.00 687.2789.270.640.000.000.000.000.002.82 697.7990.070.801.340.000.000.000.000.00 708.8191.190.000.000.000.000.000.000.00 7110.4389.570.000.000.000.000.000.000.00 7212.9785.901.130.000.000.000.000.000.00 737.4791.880.650.000.000.000.000.000.00 748.6291.380.000.000.000.000.000.000.00 757.6790.790.780.000.000.000.000.000.76 768.0491.960.000.000.000.000.000.000.00 776.8091.380.930.000.890.000.000.000.00 785.6293.730.000.000.000.000.000.000.65 799.0090.200.800.000.000.000.000.000.00 806.7993.210.000.000.000.000.000.000.00 8114.6284.201.180.000.000.000.000.000.00 8216.6480.421.060.000.000.001.880.000.00 839.5089.520.980.000.000.000.000.000.00 8412.8986.360.750.000.000.000.000.000.00 8511.0987.771.140.000.000.000.000.000.00 8612.1587.850.000.000.000.000.000.000.00 8711.0288.000.000.000.980.000.000.000.00 8814.6983.041.380.890.000.000.000.000.00 8918.2879.370.880.000.000.001.480.000.00 909.0190.050.940.000.000.000.000.000.00 91
Sample_IDQuartz Calcite Phyllo 22.0-22.423.5 27.5(KFeld) 27.8-27.9 (Plagio) 34.9other 9112.2386.940.840.000.000.000.000.000.00 9220.5377.201.420.000.000.000.000.000.85 9311.3986.981.630.000.000.000.000.000.00 9410.7987.561.650.000.000.000.000.000.00 9514.1684.131.700.000.000.000.000.000.00 9616.0382.491.480.000.000.000.000.000.00 9711.0987.930.980.000.000.000.000.000.00 989.7488.600.880.000.000.000.770.000.00 9923.8772.912.030.000.000.000.001.200.00 10024.5772.431.430.000.000.001.570.000.00 10111.3687.381.270.000.000.000.000.000.00 10213.0885.681.240.000.000.000.000.000.00 10310.2088.371.430.000.000.000.000.000.00 10414.4584.121.420.000.000.000.000.000.00 10514.4883.601.910.000.000.000.000.000.00 10631.3264.273.140.000.000.000.001.270.00 10710.7587.091.420.000.000.000.740.000.00 10832.8062.392.150.000.000.001.591.070.00 10911.7286.861.420.000.000.000.000.000.00 1109.4988.561.230.000.000.000.000.000.73 1118.3689.641.240.000.000.000.000.760.00 11215.0683.561.380.000.000.000.000.000.00 1136.9092.280.830.000.000.000.000.000.00 1148.3489.991.670.000.000.000.000.000.00 11512.9985.231.770.000.000.000.000.000.00 11619.5177.082.260.000.000.000.001.160.00 1178.0288.910.850.000.000.000.000.002.21 11810.1888.850.970.000.000.000.000.000.00 11911.8887.061.060.000.000.000.000.000.00 12016.5081.991.520.000.000.000.000.000.00 12113.1984.591.440.000.000.000.000.780.00 1226.7193.290.000.000.000.000.000.000.00 12310.0886.511.010.000.000.000.000.002.41 12410.3687.831.110.000.000.000.700.000.00 1259.2989.521.190.000.000.000.000.000.00 1269.9088.071.310.000.000.000.000.720.00 12715.3281.881.620.000.000.000.000.001.18 12811.7485.711.680.000.000.000.000.880.00 1299.1889.041.100.000.000.000.000.680.00 1309.1289.581.300.000.000.000.000.000.00 13111.7887.121.100.000.000.000.000.000.00 13211.1987.201.610.000.000.000.000.000.00 13315.9481.261.830.000.000.000.000.970.00 13410.5988.510.900.000.000.000.000.000.00 13516.0782.281.650.000.000.000.000.000.00 13610.8886.321.230.000.000.001.570.000.00 92
Sample_IDQuartz Calcite Phyllo 22.0-22.423.50 27.5(KFeld) 27.8-27.9 (Plagio) 34.90other 13721.8475.601.540.000.000.001.020.000.00 13820.9275.221.780.000.000.001.190.880.00 13917.4380.412.160.000.000.000.000.000.00 14020.6774.742.030.000.000.002.560.000.00 1417.4491.870.680.000.000.000.000.000.00 1427.3792.630.000.000.000.000.000.000.00 1438.6990.440.870.000.000.000.000.000.00 14442.4353.722.540.000.000.000.000.001.30 14550.3542.812.720.000.000.002.701.440.00 1469.1989.671.140.000.000.000.000.000.00 1475.1294.020.850.000.000.000.000.000.00 1486.8490.991.380.790.000.000.000.000.00 1499.2489.830.930.000.000.000.000.000.00 15012.4787.530.000.000.000.000.000.000.00 1515.9193.100.990.000.000.000.000.000.00 15210.6387.621.740.000.000.000.000.000.00 1539.6089.111.290.000.000.000.000.000.00 1548.7089.751.550.000.000.000.000.000.00 1559.6089.051.350.000.000.000.000.000.00 15610.8887.781.340.000.000.000.000.000.00 1579.6388.141.430.000.000.000.000.800.00 1587.9291.090.990.000.000.000.000.000.00 1598.6689.301.130.000.000.000.000.000.91 16010.2088.261.540.000.000.000.000.000.00 16110.4388.021.550.000.000.000.000.000.00 1628.7388.951.380.940.000.000.000.000.00 1638.9988.891.270.860.000.000.000.000.00 1647.0990.871.280.760.000.000.000.000.00 1653.5695.780.670.000.000.000.000.000.00 16611.4686.621.920.000.000.000.000.000.00 1678.1989.671.160.970.000.000.000.000.00 1688.8889.141.050.930.000.000.000.000.00 1695.5494.460.000.000.000.000.000.000.00 1705.1693.920.930.000.000.000.000.000.00 1719.0689.171.770.000.000.000.000.000.00 1728.7890.121.100.000.000.000.000.000.00 1736.7890.661.040.860.670.000.000.000.00 1746.76126.96.36.1990.000.000.000.000.00 1757.1091.330.900.670.000.000.000.000.00 1766.9691.580.750.700.000.000.000.000.00 17710.1987.601.490.000.000.000.000.730.00 1789.7889.081.140.000.000.000.000.000.00 1798.8384.601.720.760.000.000.000.004.09 1809.3089.611.080.000.000.000.000.000.00 1817.3390.791.180.700.000.000.000.000.00 1827.0091.081.260.000.000.000.660.000.00 93
Clay Mineral XRD Values (counts per second) Sample_IDSmectite (5.2)Illite (8.8)KaoliniteChlorite 1 2347116376.2201.8 2 2769110367.8211.2 3 2879127457.3135.7 4 2204107328.3131.7 5 2743111448.8205.2 6 300699439.6194.4 7 192150178.575.5 8 2301134408.9227.1 9 2974117467.6240.4 102915113451.8265.2 113088110509.9197.1 12187343185.080.0 133423135560.4150.6 143218124556.0153.0 153086109474.9171.1 16318798404.7166.3 17 897 2558.029.0 18164153132.043.0 19315396396.8154.2 2012383995.469.6 211646129237.586.5 22205076146.468.6 231254123177.676.4 241807145295.5138.5 253107152614.2291.8 262775142647.3150.7 272718113474.9184.1 282526100373.2135.8 29169286181.759.3 30 905102144.937.1 31 514 7057.321.7 321195217255.596.5 33 602270243.00.0 34 968261242.270.8 35 33812476.345.8 36 2282920.00.0 37 752 86104.00.0 38 62620794.00.0 39 34719253.00.0 40 880117107.00.0 41 5961530.00.0 4210128181.830.2 431210 099.140.9 44223889291.798.3 452874135402.8140.2 94
Sample_IDSmectite (5.2)Illite (8.8)KaoliniteChlorite 463625122568.4175.6 473643111561.3175.7 483043105448.5171.5 492149152380.3122.7 503211136479.5167.5 513624125630.9170.1 522313162390.6100.4 533244126516.6170.4 543580159504.9214.1 552795162373.5153.5 562070146288.397.7 572449171282.0122.0 584258125489.6162.4 593747146442.4135.6 602141146246.1113.9 612235205268.8123.2 622824190418.4130.6 632898167342.2106.8 644829150568.5169.5 651529162195.988.1 662663155267.6106.4 672952215388.7134.3 681685202191.6105.4 693403145354.291.8 702606162326.675.4 712087236273.4125.6 723128176376.5125.5 734268139461.5143.5 745872133731.4164.6 752220233338.087.0 761868251236.4109.6 772381203310.8113.2 781996222224.3115.7 793613176360.5135.5 802706192255.5117.5 812109218192.474.6 823639206346.2130.8 835675164675.2186.8 843084206304.8161.2 854306134378.8138.2 864404151517.2117.8 874056159531.8155.2 883266216409.0186.0 893516174454.8162.2 903862140555.3190.7 913825144480.3143.7 923742144386.1181.9 95
Sample_IDSmectite (5.2)Illite (8.8)KaoliniteChlorite 93 4005128418.4168.6 94 4654111403.5171.5 95 4191127505.3156.7 96 5482138541.1230.9 97 5235124508.0254.0 98 4993120433.7181.3 99 3619157335.3120.7 1005145133550.6226.4 1014854131476.6145.4 1025457174559.2226.8 1035215148576.4194.6 1045180102334.3148.7 1054108147557.1194.9 1063742239266.191.9 1074687120337.7132.3 1086064200511.8222.2 1095383126402.9119.1 1104185116394.1146.9 1114711132308.3112.7 1124283232246.6109.4 1132228118191.989.1 1144339153224.488.6 1154004174293.890.2 1163348129266.9106.1 1173779138232.598.5 1183896148184.285.8 1194945281238.6108.4 1204308140266.1119.9 1214671179322.0110.0 1224803135302.966.1 1234714146275.6135.4 1243559112313.173.9 1254760146288.5103.5 1264933127283.095.0 1274339157301.0105.0 128246915587.447.6 1295457219252.490.6 1301732183109.558.5 1314126100235.870.2 1324288106201.974.1 1333035161187.486.6 1343881128227.997.1 1353961121208.578.5 1365123171486.1131.9 1374200135358.9129.1 1383510155203.891.2 96
Sample_IDSmectite (5.2)Illite (8.8)KaoliniteChlorite 1393483 121299.3111.7 1405102 137403.6137.4 1414182 124433.2120.8 1422041 93216.385.7 1432394 131280.5121.5 1443795 172234.097.0 1452203 93112.054.0 1462264 169301.198.9 1473845 158196.477.6 1482978 144229.3100.7 1492632 123190.466.6 1503012 119154.188.9 1512523 123241.593.5 1525265 145433.7117.3 1533751 191303.3114.7 1543363 166262.5109.5 1552975 181271.586.5 1562355 189275.092.0 1573912 102181.770.3 1583435 155310.4111.6 1593499 178453.896.2 1603603 185414.390.7 1611847 218179.470.6 1621762 185199.177.9 97