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Constraining the Geometry and Evolution of the Maneadero Basin, Baja California, Mexico by Sean Callihan A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology Department of Geology College of Arts and Sciences University of South Florida Major Professor: Paul Wetmore, Ph.D. Charles Connor, Ph.D. Sarah Kruse, Ph.D. John Fletcher, Ph.D. Date of approval: February 11, 2010 Keywords: gravity survey, structure, microplate motion, Agua Blanca fault, basin geometry Copyright 2010, Sean Callihan
Acknowledgements I would like to thank my committee members Drs. Paul Wetmore, Chuck Connor, Sarah Kruse, and John Fletcher for their support in this project. I would also like to thank Adam Springer, Jeff Beeson, Oscar Gonzalez, and James Wilson for their help collecting data over the last two summers. I am very grateful for the help, guidance, and moral support of my family and friends. To my dad, thanks for keeping things in perspective for me and continuing to guide me trough the good times and the bad. To the Patterson family, words cannot fully reveal how gratefully I am to have you all in my life. Lastly, I would like to thank some of my friends at USF: Adam Springer, Jeff Beeson, Ja mes Wilson, Cosmin Stremtan, Jenn Sliko, Dorien McGee, Angela Dippold, and Julie McKnight, just to name a few. I am also grateful to Armando Saballos, and Koji Kiyosugi for helping me with my data.
i Table of Contents List of Figures iii List of Tables v Abstract vi Chapter 1: Introduction 1 Chapter 2: Background 7 2.1 Geology 7 2.2 Agua Blanca Fault 11 2.3 Associated Faults 14 2.4 Baja Microplate 16 2.5 Previous Geophysical Studies 17 Chapter 3: Methods 19 3.1 Datasets 19 3.2 Structural Mapping 20 3.3 Gravity Survey 20 3.4 Magnetics 25 3.4 Modeling 26 Chapter 4: Results 27 4.1 Structural Mapping 27 4.2 Gravity Survey 30 4.3 Profile Models 32 Chapter 5: Discussion 42 Chapter 6: Conclusions 48
ii References 49 Appendices 59
iii List of Figures Figure 1 Regional Map 2 Figure 2a Block Model A 4 Figure 2b Block Model B 4 Figure 2c Block Model C 4 Figure 3 DEM of the Maneadero Basin and faults 5 Figure 4a Regional Geology 9 Figure 4b Geology of study area 10 Figure 5 Photo of the scarp in Valle Santo Toms 13 Figure 6 Vectors of GPS stations in Northern Baja California 16 Figure 7 Location of gravity stations 20 Figure 8 Photo of the fluvial terraces at Las Animas 28 Figure 9 Photo of the slide block/normal fault on the Punta Banda Ridge 29 Figure 10 Gravity map 31 Figure 11 Location of profile models 33 Figure 12 Profile A and B 37 Figure 13 Profile C and D 38 Figure 14 Profile E and F 39 Figure 15 Profile G and H 40 Figure 16 Basin depth map 41
iv Figure 17 Bathymetric map 46
v List of Tables Table 1 Base Stations with locations and elevations 22
vi Constraining the Geometry and Evolution of the Maneadero Basin, Baja California, Mexico Sean Callihan ABSTRACT The Maneadero Basin is identified as a transtensional sedimentary basin along the Agua Blanca Fault (ABF) in the southern limit to the Big Bend Domain of the North American-Pacific plate boundary zone. The ABF exhibits both the dextral and normal components of slip. This creates an interesting setting for the formation of the Maneadero Basin because structures with orientations similar to the ABF are typically contractional (e.g.: Puente Hills Fault, Whittier Fault, and Rancho Cucamonga Fault). The question if this basin is evidence of pl ate-scale transtension or local extension associated with bends/stopovers along the ABF is addressed by this study with three working hypotheses. The hypotheses presented by this study are: 1) the basins formed by a dip-slip component on the ABF and truly are an expression of regional transtension, 2) the basins formed at right steps along the dextral ABF, or 3) the basins formed as a result of juxtaposing basement blocks with disparate topographies. Each of these hypotheses would produce unique basin geometries and structures within and around the Maneadero Basin. To test these aforementioned hypotheses, a multi-disciplined study was conducted in the basin. A structural dataset was collected to identify kinematics and offsets of faults both within and bounding the basin. A gravity survey was also conducted to image the basin geometry.
vii The results of the study show an asymmetrical gravity anomaly that closely follows the trace of the ABF. The amplitude of the anomaly is 54 mGal, the gradient of which is steepest around the ABF and shallows away from the fault to the north and east. Forward models of this anomaly indicate the ABF is a steeply north dipping fault. The gravity anomaly also indicates that the deepest part of the basin is located close to, but not coincident with the ABF and the basin gradually shallows to the northeast. This geometry is consistent with the hypothesis that the basin results from dip-slip on the ABF. This idea is also supported by the structural data, which includes fluvial terraces that have been uplifted and offset by faulting on the ABF, and by the presence of a normal fault on the ABF in the center of the basin. The third hypothesis is also supported by models of the gravity data, which suggest a deep (~900m) bowl shaped erosional feature in the bedrock. Dextral slip on the ABF juxtaposes the topographically high Punta Banda Ridge with this topographically low feature. Overall, the data presented in this study suggest the formation of the Maneadero Basin results from is a combination of the dip-slip component on the ABF and juxtaposition of the topographically elevated Punta Banda Ridge with a topographically lower basin of Bahia Todo Santos and Valle Maneadero. Geodetic data strongly suggest that the difference in motion of the Baja Microplate (south of the ABF) to the disrupted southern California Block (north of the ABF), and the orientation of the ABF relative to that motion, is causing transtension in the Maneadero Basin. This combined with strike-slip juxtaposition of different topographies allowed for the formation and evolution of the Maneadero Basin.
1 Chapter 1 Introduction Sedimentary basins are a common feature throughout the world. In terms of the tectonic settings of their formation they ar e found in divergent, intraplate, convergent and transform settings (Ingersoll, 1988; Ingersoll and Busby, 1995). Along transform margins or transcurrent faults within continents, a range of basin types can result from various characteristics of strike-slip faulting (Nilsen and Sylvester, 1995). Wrench faulting, step-over faulting, block rotations, releasing bends along the fault and relative plate motions are some of the most prominent means by which sedimentary basins can form along strike-slip faults (Blick and Biddle, 1991). The San Andreas Fault (SAF) along the western coast of North American contains several basins such as the San Bernardino basin (step-over faulting) and the smaller basins of the Eastern Transverse Ranges (block-rotations) formed as a result of these processes (Morton and Matti, 1993; Langenheim and Powell, 2009). Several smaller faults associated with the SAF exist due to the transfer of strain around the big bend in the SAF. Faults in this area can have extensional or contractional characteristics. For example, the Laguna Salada fault (strike 321) and the Sierra Juarez fault (strike 345) are characterized by extensional to transtentional kinematics (Mueller and Rockwell, 1995). Alternatively, faults within this same zone can be contractional. Such faults include the Witter fault (strike 291), Puente Hills fault (strike 290), and Rancho Cucamonga fault (strike 260) (Crook et al., 1987; Wright, 1991; Shaw et al., 2002; Brankman and Shaw, 2009).
2 As a structure within the Big Bend Domain of the North American-Pacific plate boundary zone and a part of the San Andreas system of faulting, the dextral ABF represents the southernmost fault in the system that transfers slip out of the Gulf of Figure 1: Regional map of the study area. Heavier line represents the trace of the southern portion of the San A ndreas Fault (SAF). Lighter lines r epresent other smaller faults in t he region. Fault names are: ABF (Agua Blanca Fault), SMVF (San Miguel Vallecitos Fault), SPMF (San Pedro Martir Fault), SJF (Sierra Juarez Fault), LSF (Laguna Salada Fault), CBF (Coronado Bank Fault), EF Z (Elsinore Fault Zone), PVFZ (Palos Verdes Fault Zone), PHF (Puente Hills Fault), WF (Whittier Fault), and RCF (Rancho Cucamonga Fault). Brown areas represent basins that exist along the trace of the ABF. Names are: VM (Valle Maneadero), VSF (Valle Santo Toms), VAB (Valle Agua Blanca), VT (Valle Trinidad)
3 California and into the Continental Borderlands on the west side of Baja California. The trace of the ABF can be as much as ~45 counter-clockwise from that of the southern SAF. Thus its orientation is sub-parallel to the Traverse Ranges and the associated thrust faults to the north (Allen et al., 1960). Orientations such as these within the system should be experiencing contraction (e.g.: Whitter fault and Puente Hills faults), however, several small basins exist along the Agua Blanca fault (e.g.: Valle Maneadero, Valle Santo Thomas, Valle Trinidad) which are interp reted to have formed within a extensional to transtensional regime (Gastil et al., 1975; Hatch, 1987; Schug, 1987; Hilinski, 1988; Legg et al., 1991). The question is if these basins are evidence of plate-scale transtension or local extension associated with bends/stopovers along the ABF. In this study, several working hypotheses are tested to answer this question: 1) the basins formed by a dip-slip component on the Agua Blanca fault and truly are an expression of regional transtension, 2) the basins formed at right steps along the dextral Agua Blanca fault, or 3) the basins formed as a result of juxtaposing basement blocks with disparate topographies. Each of these hypotheses would produce unique basin geometries and be associated with specific structures. Therefore, a detailed study involving geophysical and structural methods is used to differentiate between these hypotheses. For example, a basin formed by a dip-slip component on the ABF, the first hypothesis, would form an asymmetrical basin with the long axis paralleling the ABF and the deepest part located against the fault (Figure 2a). Basins formed under conditions outlined in the second hypothesis would show a rhomohedral shaped basin with steep boundaries and normal faults bounding the east, west, or both sides of the basin. In the study area the eastern
4 Figure 2a: Simplified block models illustrating basin geometries and fault orientations for the aforementioned hypotheses. The heavy black line represents the ABF and the kinematic indicators show motions of the blocks relative to one another. The front face of each model is a cut-away showing the basin geometry at depth. This model shows a basin that has formed solely by dip-slip along the ABF. Figure 2b: A block model illustrating basin formation in a step-over scenario. Notice the normal fault the forms to accommodate the opening of the basin. Presumably there would be a counterpart bounding the opposite side of the basin in a similar manner. Figure 2c: A block model illustrating a basin that formed by juxtaposing topographically lower basement with higher basement. Notice the gradual slope rising to the east which tapers the basin fill in this direction.
5 normal fault would most likely be situated around the town of Maneadero. The deepest part of this basin would most likely be near the center of the basin just offshore in Bahia Todos Santos (Figure 2b). A basin formed by the third hypothesis displaces a sloped margin and juxtaposes high topography with lower creating an asymmetrical basin. In the study area this margin would be the western coastal slope of Baja California. The long axis of the basin would be oriented perpendicular to the ABF and would have a gradual slope rising from the deepest part of the basin eastward to the town of Maneadero (Figure 2c). Figure 3: Digital Shaded relief model of the fi eld area rendered from SRTM data (Jarvis et al., 2006). Solid lines represent the mapped trace of faults in the area. Dashed lines mark the inferred and offshore location of the faults. Dashed red line roughly marks the boundary of the Maneadero Basin.
6 The Maneadero Basin serves as the study area to test the aforementioned hypotheses. It is the western-most basin found along the ABF and includes Bahia Todos Santos (Figure 3). The Maneadero Basin is located in the northwest corner of the Baja California peninsula, about 170km south of the USA/Mexico border at San Diego, CA. The basin is asymmetrical in shape with the long axis oriented NW-SE and is bounded by mountains to the southwest and east. The most prominent mountains are associated with the Punta Banda Ridge to the southwest that rises ~1000m above the valley floor. The on-land portion of the basin is heavily farmed because the basin fill is composed of alluvial, fluvial, and marine sediment with the upper 60-80m consisting of highly porous gravels and sands creating a natural aquifer sy stem (Daessle et al., 2003). Farming has also provided many roads and paths which make most of the basin accessible for the structural and geophysical surveys. The Maneadero basin has also been studied (e.g.: Gonzalez-Serrano, 1977; Pohle, 1977; Vazquez, 1980; Cruz, 1986; Aguero, 1986; Legg et al., 1991; and Perez-Flores et al., 2004) more thoroughly than the other basins along the ABF, which gives this study a unique opportunity to test the conclusions of other structural studies and incorporate their data into this study.
7 Chapter 2 Background 2.1 Geology The bedrock geology of the northern portion of the Baja peninsula is characterized by four main geologic entities; a central zone, the Santiago Peak arc segment, the Alisitos arc segment and the Peninsular Ranges Batholith (PRB, Figure 4a). The central zone is composed of turbidite deposits that were emplaced in the medial to distal portions of a submarine fan (Gastil, 1993). These Late Triassic Jurassic deposits range in age from 210 Ma (Bedford Canyon Formation) to 150 Ma (French Valley Formation) and are found from southern California/northern Baja to southern Baja (Gastil and Girty, 1993; Wetmore et al., 2003). Wetmore et al. (2003) argue that these deposits were combined into an accretionary wedge at the western margin of North America along the trench that persisted there during the middle portion of the Mesozoic. To the west of the central zone and north of the ABF, the Santiago Peak arc segment is part of a continental margin arc that formed in the early Cretaceous built upon the Triassic-Jurassic accretionary wedge (Wetmore et al., 2002, 2003). Basal lava flows of the SPV have been dated at 127 +/2 Ma. Additional ages from the SPV range between 116 Ma and 128 Ma (Anderson 1991, Meeth 1993, Carrasco et al 1995). The Alisitos Arc segment is found west of the central zone as well, but south of the ABF.
8 This arc represents an exotic island arc, which was accreted onto the western edge of North America in the latest Early Cretaceous at about 108-100 Ma. The Alisitos Formation, the principal unit of the Alisitos arc, consists of sub-aqueous tuffs and pillow basalt lava flows with interbedded volcaniclastics (Allison, 1974; Wetmore et al 2002, 2003). The Alisitos arc is bounded on the east by the Main Mrtir thrust (Johnson et al., 1999) and to the north by the ancestral Agua Blanca Fault (aABF; Wetmore et al., 2002, 2003). The aABF is thought to be the along strike continuation of the Main Mrtir Thrust and juxtaposes the Santiago Peak arc to the north and the accreted Alisitos arc (Wetmore et al., 2003). These contractional structures accommodated the suturing of the Alisitos arc to the North American continental margin during the latest Early Cretaceous. The aABF is oriented subparallel to the trace of the western portion of the active ABF. Its mapped trace places the aABF ~2-3 km south of the active ABF along the entirety of Valle Agua Blanca and is inferred to be intimately associated with the Santo Toms and ABF within Valle Santo Toms. Furthermore, the aABF has been inferred to have been exploited by the active ABF at depth and may be responsible for the orientation of the active fault throughout its western extent (Wetmore et al. in review ). The PRB is one segment of a suite of Jurassic and Cretaceous batholiths that extend from Alaska to Central America (Armstrong, 1988; Daley, 1933). In the area of Baja and southern California, the PRB is characterized by plutonic intrusive rocks that typically plot as Quartz-Diorite and tonalites on the west side and granodiorites to granites in central and eastern portions of the PRB (Gastil et al 1975). The plutons of the PRB intrude each of the aforementioned three zones. The ages of emplacement range from 134 Ma to 97 Ma (Silver and Chappell, 1988: Walawender et al., 1991).
9 Figure 4a: Simplified geology of southern California and northern Baja. This figure is modified from Wetmore et al 2003.
10 Figure 4b: Geology of the field area superimposed on a shaded relief DEM. Notice the pink plutonic intrusion in the lower right corner which has been cut by the ABF. The offset of this pluton gives a total amount of slip since the inception of the ABF of ~7km.
11 2.2 Agua Blanca Fault The overall length of the ABF consists of an onshore and offshore portion (Figures 1 and 3). The onshore portion of the fault is about 125-130km and extends from San Matas Pass in the east, where the ABF meets the San Pedro Mrtir fault, west to the Pacific Ocean at Punta Banda south of the city of Ensenada (Figure 1). There are several small sections associated with this fault. From east to west there are two small narrow valleys (Valle Trindad and Caon Delores-Valle Agua Blanca) and two sedimentary basins (Valle Santo Toms and Valle Maneadero). The trend of the ABF through the two basin is more northerly than through the two valleys found further east. In Valle Trinidad through Valle Agua Blanca the trend is roughly 280, ~45 counterclockwise from that of the southern portion of the San Andreas Fault (Hatch, 1987; Hilinski, 1988). Through Valle Santo Toms the fault has a trend of ~293 and in Valle Maneadero a trend of ~302 (Allen et al., 1960; Schug, 1987). From here the ABF enters the Pacific Ocean at Punta Banda. The offshore segment of the ABF continues to change in trend as it transitions into the Continental Borderlands fault zone which trends ~330 (Legg et al., 1991). The fault most likely links up with the Coronado Bank Fault. However, it is difficult to identify the exact location of this transition due the very complex fault zone that exists between Punta Banda and Islas Los Coronados, which are ~20km offshore of Tijuana, Mexico (Legg et al., 1991). The kinematics of the ABF have been inferred from numerous geomorphic features throughout the length of the fault (Allen et al., 1960). The easternmost evidence of dextral displacement is located in Valle Trinidad by several streams which are offset by 15 to 30 m. Dextral slip rates are estimated to be 1 mm/yr since the mid to late
12 Quaternary. Fault scrap profiles in this area also suggest vertical slip rates of 0.2 to 4.0 mm/year on the ABF (Hilinski, 1988). Valle Agua Blanca and Caon Delores to the west of Valle Trinidad also contain evidence of dextral faulting on the ABF. Alluvial fans in Valle Agua Blanca are offset by as much as 4.8 km (Allen et al., 1960). These lateral offsets and 14C calibrated soil chronosequence yields a slip rate of 4 to 6 mm/yr for the late Quaternary (Hatch, 1987; Rockwell et al., 1989). Interestingly, the sense of slip in this section is almost purely strike-slip with vertical displacements isolat ed to small, disparate strands of the ABF (Hatch, 1988). There are also two small (<200m) step-overs located at the east and central section of the valley. The eastern step-over is a left step in the dextral ABF creates a compressional regime, which is illustrated by a pop-up structure. The central step-over is a right step in the ABF creates a small depression (sag) which has been filled with erosional sediments from the adjacent mountains (Hatch, 1987; Rockwell et al., 1989). In Valle Santo Toms the ABF runs on the north side of the basin. The fault is concealed in most places by Quaternary deposits such as landslides or alluvium (Allen et al., 1960). Evidence of faulting is demonstrated by fault scraps and offset terraces. These features show almost pure strike-slip style of faulting on the ABF. A small vertical component is also present on the fault as demonstrated by a 2 m high scarp located near the central north-side of the basin (Figure 5) (Alsleben, personal correspondence; Wetmore, personal communication; and Springer, 2010).
13 In the area of Valle Maneadero, geomorphic evidence of slip on the ABF is well expressed in three areas: Las Animas, the center of the basin, and the western section of Punta Banda. Las Animas, in the southeast corner of the field area, has a series of offset fluvial terraces, which have been displaced by dextral and normal slip on the ABF. The trace of the fault here is confined to two strands (Madsen, 2009). The south strand is marked by a line of trees, which resulted from an aquitard effect along the fault. Dextral slip rates along the ABF are calculated to be 4.3 to 6.0 mm/yr based on mapping and soil chronology of alluvial deposits (Schug, 1987). Near the center of the basin the trace of the ABF splays into several smaller branches with smaller offsets (Madsen, 2009). At the western end of Valle Maneadero there are a series of marine terraces on the Punta Banda Ridge which further suggest a normal component of displacement on the ABF. These terraces record ~16 to 29 mm/ka of vertical displacement dating back to at least ~450 ka (Rockwell et al., 1989). However, not all of this vertical uplift is directly related to slip on the ABF. A similar rate of ~30 mm/ka has been calculated for much of Figure 5: A photo of a fault scarp on the north side of Valle Santo Thomas. Yellow dashed line marks the location in the foothills. Scarp is about 2m high according to Dr. Helge Alsleben (personal communication).
14 the coast from northern California to northern Baja California (Muhs et al., 1992). This suggests that the coast is being uplifted as a whole by a regional process with slight alteration due to individual crustal blocks along faults such as the ABF (Muhs et al., 1992). Recent work using GPS geodesy suggests that at present the entire ABF has a dextral slip rate closer to 2.5mm/yr (Dixon et al 2002). This reduction in the rate is thought to be a product of slip being taken up by the San Miguel-Vallecitos Faults (SMVF). These faults are much younger structures with minimal offsets and are better aligned with the Pacific-North American plate motions suggesting that the Agua Blanca fault may be either abandoned or accumulating strain at a slower rate (Dixon et al., 2002). 2.3 Associated Faults Several other local faults exist and may be important to the kinematics of the ABF. Such faults include the Santo Toms fault, Maximinos fault, and the Estero Beach fault. In Valle Santo Toms, motion on the ABF is almost purely strike-slip and extension is being accommodated mostly by the Santo Toms fault, which bounds the south side of the basin. At the western end of the basin the Santo Toms fault has a strike and dip of 322, 70 (Springer, 2010). Dip-slip faulting is demonstrated by recent scarps in the valley floor and several large springs along the trace of the fault (Allen et al., 1960). Between the western corner of Valle Santo Toms and the Pacific Coast at Punta Soledad, faulting appears to be less well defined and slip may be lost to the Maximinos Fault to the north. The Maximinos fault is located on the south side of the Punta Banda Ridge and accommodates approximately 1.6mm/yr of dextral slip (Schug, 1987) (Figure 4b). There
15 is also a clear normal component of slip on this fault as demonstrated by disturbed submarine sediment layers in seismic profiles (Legg et al., 1991). A vertical slip rate of ~1mm/yr is estimated for the Maximinos fault based on uplifted coastal terraces on the south side of the Punta Banda Ridge (Rockwell et al., 1987; Schug, 1987). This fault is inferred to extend from the Santo Thomas fault in Valle Santo Thomas and into the Pacific Ocean where it likely dies out into the more dominant ABF (Schug, 1987) (Figure 3 and 4b). The Estero Beach fault is inferred to extend from just north of Valle Agua Blanca, through the middle of Valle Maneadero, and into Bahia Todos Santos. The location of this fault in Valle Maneadero is marked by a line of denser vegetation than the surrounding area, which likely resulted from an aquitard effect along the fault. Location of the fault to the east of Valle Maneadero is inferred from aerial photographs (Wetmore, personal correspondence) and in Bahia Todos Santos by a small seismic swarm in 1981 (Figure 4b). Focal solutions calculated from this swarm suggest the faulting is dextral (Gonzalez and Suarez 1984). This fault is not as well expressed as the ABF, however, truncated marine sediments can be seen in seismic profiles conducted in Bahia Todos Santos (Legg et al., 1991). These profiles show the Estero Beach fault as being much less significant than the ABF. The amount of normal displacement on this fault is shown in the profiles to be on the order of 10s of meters, which is significantly less than the displacement found on the ABF (~7 km dextral and ~300 m vertical (Rockwell et al., 1987)). This Estero Beach fault has been interpreted to be a right handed step-over fault driving basin subsidence similar to that described above in the second hypothesis (Legg, 1985; Legg et al., 1991). 2.4 The Baja Microplate
16 The Baja Peninsula was originally thought to be situated on the Pacific plate that is currently moving in a northwesterly direction at a rate of ~52mm/yr relative to the North American plate (Atwater, 1970; Atwater and Stock, 1998; DeMets and Dixon, 1999). Recent GPS geodetic studies suggest that Baja California behaves as a microplate. This microplate moves at a rate ~10% slower and with a more westerly direction of motion than the Pacifc plate (Plattner et al., 2007). The lack of faults south of the ABF Figure 6: A map of the residual vectors of motions of the stations north of the ABF. These motions are calculated with respect to a stable Baja California reference block which is south of the ABF. Arrows denote direction and magnitude and the ellipses denote the amount on uncertainty.
17 suggests that the peninsula is moving as a ridged block with the northern boundary being marked by the ABF (Malservisi, personal communication; Plattner et al., 2007). Across the ABF a change in the direction of motion of GPS Geodetic sites can be observed (Figure 6). A total of 24 stations were used to calculate vectors of the sites north of the ABF with respect to sites south of the ABF (stable ridged Baja California block). The residual vectors suggest an average azimuth of 122 + 7 at a rate of 3.0 + 0.9 mm/yr. 2.5 Previous Geophysical Studies Several geophysical surveys including seismic, magnetic, and gravity have been conducted in the Maneadero Basin and Continental Borderlands. The marine seismic surveys show not only show a complex transition of the ABF into the Continental Borderlands, but also that the ABF is a steeply northward dipping fault (Legg 1985, Legg et al., 1991). Gonzalez-Serrano (1977) and Pohle (1977) conducted some of the initial gravity surveys for the Manedero area and were later followed by Vazquez (1980), Cruz (1986), and Aguero (1986). Individually, these survey s covered small portions of the Maneadero Basin or the ABF. For example, Pohle (1977) was mainly concerned with the fault geometry of the ABF and covered a small segment of the ABF in the Maneadero Basin located near the eastern tip of Estero Punta Banda (Figure 3). Similarly, GonzalezSerrano (1977) focused mainly on the offshore portion of the basin in their marine gravity survey. These surveys remained isolated until Perez-Flores et al (2004) combined the previous work into one homogeneous dataset. Theirs is the most comprehensive and regionally pervasive dataset of the Maneadero Basin that provides insight into the gravitational anomalies, basin geometry, and f aulting of the study area. Based on this
18 study the gravity signal is shown to be fair ly asymmetrical in map view with a steep gradient on the south side of the basin adjacent to ABF. This study also identifies minor gradients located near the city of Maneadero which are interpreted as smaller faults oriented perpendicular to the ABF. The basin floor is estimated to be about 1500 m below sea-level at its deepest point near the middle of Bahia Todos Santos and gradually shallows to the north and east (Perez-Flores et al., 2004).
19 Chapter 3 Methods 3.1 Data Sets A combined mapping and gravity survey of the Maneadero Basin was used to test the competing hypotheses. The mapping portion of this study was conducted to identify characteristics of faults bounding and within the basin. These characteristics include location, trend, length, offsets, and kinematics. Gravity data were collected because the density differences between the basin fill and basement cause measurable variations in local gravity. Because gravity anomalies are largely sensitive to the thickness of sediments above the basement, the data can be used to constrain basin geometry, which is necessary for testing the three competing hypotheses described above. Forward modeling of the gravity anomalies can also be used to help constrain fault orientations. In this study, data were collected in two critical places: outside the basin, to fully capture the shape of the gravity anomaly, and inside the basin to increase the spatial resolution of gravity stations from previous studies. Several 2-D models of the Maneadero Basin were developed that best fit the structural mapping observations and the resultant gravity data. These models were then used to test the three working hypotheses.
20 3.2 Structural Mapping During the summers of 2008 and 2009, mapping of the study area was conducted to locate, and describe faults both bounding and within the basin. The data obtained includes fault orientation, location, length, slip direction, offsets, etc. where available. 3.3 Gravity Survey Gravity measurements were taken during summer 2008 and 2009 with a ZLS Burris gravity meter at stations both within and outside of the Maneadero Basin. A LaCoste and Romberg gravity meter was also used for the more remote stations such as Figure 7: A DEM map of the Maneadero Basin and the location of gravity stations. Brown dots represent gravity stations from other studies which were complied and homogenized by PerezFlorez (2004). Red dots represent grav ity stations collected for this study.
21 those on the north slopes of the Punta Banda Ridge. These instruments have an accuracy of 0.001 and 0.01 mGal, respectively. The majority of the stations are spaced at 500 m intervals; however, the spacing was reduced to 250m around areas with high gradients to fully and accurately capture the shape of the gravity anomalies. Location of each station was obtained using a Leica GS20 Differential GPS system with an accuracy of 1 cm in both the horizontal and vertical positions. Typical gravity reductions were used to process the data including tidal drift, instrument drift, free air, latitude, Bullard A (Simple Bouguer), Bullard B, and Bullard C (Terrain). Below is a discussion of each step taken to reduce the data. Tidal Correction A FORTRAN program based on equations from Longman (1959) was used to calculate the gravitational effect of excess/reduced mass during high/low tides during each day of data collection. These values were used to correct the observed gravity measurements at each of the stations. Ideally this type of correction would not be necessary if base station check-ups were frequent ( 1 hour) however, due to the scale of this survey we could not return to the base station every hour. Therefore, this correction is an important step the data reduction process. Maximum tidal correction values for the Maneadero area during this survey were +/-0.16 mGal. Drift Correction During the course of a survey the instrument readings naturally drift. To account for this drift, measurements were periodically taken at a base station. Each day a base station reading was taken before other measurements were collected. The base station was then revisited 3-4 times during the day. This process was repeated every day of
22 data collection. Two base stations were used to help reduce the amount of time traveling to and from the base station. Deviations from the base station readings throughout the day were used as our correction values for this step. On any given day the magnitude of instrument drift for the LaCoste & Romberg gravity meter was 0.80 mGals. The ZLS Burris instrument had a drift of 0.05 mGal/day. A second drift correction was also implemented to account for the time between the 2008 and 2009 surveys. This value was determined by taking a gravity measurement at the Hidalgo statue during each of the surveys. The magnitude this drift was approximately +3.47 mGals which was subtracted from the 2009 survey, and then combined with the 2008 survey. Free-Air correction The standard free air correction equation used is where h is elevation of the gravity station relative to the datum. This is a modified form of the Grant and West (1965) equation. The reason for the modification is because certain terms in the longer equation are either already accounted for in the other corrections or are very small and therefore, can be ignored (Burger et al 2006). We note that our 1 cm Station NameLatitudeLongitudeElevation Base 131.694 116.62832.21 Base 231.736 116.6405.25 Hidalgo Statue31.936 116.63016.22 Table 1: A list of the stations used in this study and their relative locations and elevations
23 uncertainty in elevation corresponds to an uncertainty in 0.03 mGal in the Free-Air correction. Latitude Correction The gravity anomaly as a function of latitude on the earths surface is given by where is latitude (Telford et al 1990). This equation accounts for the fact that observed gravity readings increase toward the poles. Due to the scale of the survey it was necessary to apply the latitude correction, which varied by 18 mGal from the northernmost site to the southernmost site. Bullard A (Simple Bouguer) The Bullard A correction accounts for additional mass between the observation point and the datum. This correction assumes the mass is a homogeneous infinite flat slab with a thickness equal to the height of the observation point from the datum. The equation is where is the density of the mass, and h is the height of the observation point. The density used for this correction was determined analytically using a method developed by Paranis (1976) to solve for bulk density below gravity stations. This method uses the Bouguer corrected gravity plotted against height of the station. The bulk density is determined by the best fit line through the data points. This method was applied to a transect of data across the Punta Banda Ridge extending from the north side of the ridge, near the eastern tip of Estero Punta Banda, to the south side of the Ridge. This
24 transect was chosen because it showed significant topographic variation over the Punta Banda Ridge. The result was a bulk density of 2.66 g/cm3 for the Santiago Peak basement rocks. Bullard B In gravity surveys with large areas the Bullard A correction needs to be adjusted to account for the curvature of the Earth. The Bullard B correction adjusts from the flat slab to a spherical slab approach (Bullard 1936, Nowell 1999). The equation from Cogbill (1979) is where h is the height of the observation point from the datum. The coefficients above give a spherical slab approximation which extends out 167 km from the observation point. Cogbills (1979) equation assumes a density of 2.67 g/cm3 and a radius of 6371 km for the Earth. Bullard C (Terrain Correction) This correction accounts for the small scale changes in mass due to the topography around the observation point, which are not addressed by the Bullard A correction. A PERL script was used to calculate the effect of topography as far as 5km away from each station. A Digital Elevat ion Model (DEM) from NASAs Shuttle Radar Topography Mission (SRTM) with a 90m resolution of the Maneadero area served as the topography data for this correction. The equation used in the PERL script is from Plouff (1976), a flat-topped prism approach. It is important to note that a more detailed DEM (i.e.: <90m) would enhance the precision of this correction; however such a DEM for the Maneadero area does not exist.
25 The corrected data is presented as a anomaly relative to an absolute gravity station located in the city of Ensenada, Mexico (Hidalgo Statue). This was accomplished by correcting the data using the Hidalgo station as the reference. Gravity measurements collected by previous studies (Vazquez 1980, Cruz 1986, and Aguero 1986, GonzalezSerrano 1977, and Gonzalez-Fernandez 2000) were compiled and homogenized by Perez-Florez et al (2004) and amended to the 382 station dataset collected by this study. This was accomplished by a simple direct shift to the amended dataset, the value of which is the difference between measurements at stations common to both datasets. The combined dataset includes 1257 gravity stations across the Maneadero basin and Bahia Todos Santos (Figure 6). 3.4 Magnetics A magnetic survey of the Maneadero Basin was also conducted to better constrain the basin geometry and fault orientations. Magnetic measurements were collected using a Geometrics G-858 magnetometer and locations were obtained with a GPS datalogger. Each machine was time-synchronized with collection rates of one reading per second. The two data files were time-stamped matched using a PERL code. The resultant file contained magnetic readings and their associated GPS locations. A total of 70,348 magnetic measurements were collected, which closely follows the path of the gravity survey. The basin is heavily fa rmed and has areas that contain barb wire, power lines, and steel rebar could throw off the magnetic readings. Despite best efforts to avoid these areas, the resultant dataset is of relatively low quality and not included in the modeling. This data might be useable for future studies and therefore is listed in Appendix B. 3.5 Modeling
26 The modeling of the gravity and structural data was performed using Geosoft Oasis Montaj software. The corrected gravity observations were imported into the program and a minimum curvature algorithm was applied to the data points to produce a 2-D gravity anomaly map of the basin. An upward continuation filter was also applied to remove short wavelength (< ~500 m) anomalies presumed to be associated with instrument errors and minor discrepancies between the combined datasets. The gravity signal associated with basin boundaries and faults is expected to reflect discontinuities at depths greater than hundreds of meters, and hence should be preserved in the longer wavelength anomalies. To model basin depths and fault orientations, 2D profiles were also constructed in Oasis Montaj, both parallel and perpendicular to the ABF. In each profile basement rock density was set to 2.66g/cm3, the same as the Bullard A correction, and the basin fill density was given a density of 2.0g/cm3. This basin fill density value was chosen for three reasons. First, it coincided with the density contrast presented in previous studies around the Maneadero area (Perez-Florez et al., 2004). Second, this value is the average value given for basin fill sediments (Burger et al., 2006). Finally, through a series of trial and error models using different basin fill densities the best forward models resulted from using 2.0 g/cm3.
27 Chapter 4 Results 4.1 Structural Mapping Mapping conducted in the summer of 2008 and 2009 identified two key features along the trace of the Agua Blanca fault. One feature, located in the southeast corner of the Maneadero Basin, is an Early Cretaceous pluton (Kqd on figure 2b) that has been cut and offset by dextral slip on the ABF. The amount of offset is approximately 7 km based on the measured distance along the fault of the intersection between the NWmargin of the intrusion with the fault. Given that the offset feature is a Cretaceous intrusion, the 7 km of displacement is interpreted to represent the total offset for this part of the ABF. Mapping of the Las Animas section of the Maneadero Basin shows the ABF as being contained to 2 strands. The northern strand is characterized by a ~30m wide damage zone which demonstrates dextral offset by a beheaded stream and a series of fluivial terraces. In all there are 5 distinct terraces (Figure 7). Terrace 1 (T1) is the currently active terrace and increase in age to Terrace 5 (T5). These features show both dextral and vertical offsets. T2 shows this feature clearly with ~7m of dextral and ~1.5m of vertical offset.
28 Figure 8: A photo of the offset fluvial terraces in Las Animas. This view is looking south with the Punta Banda Ridge rising in the background. T he Terraces are marked as T1-T5. They increase in age with the youngest being T1 (active fl uvial terrace) to T5 (oldest fluvial terrace at Las Animas). The dotted black line marks the Agua Blanca Fault (ABF). The offset of T2 mentioned in the text is not clearly seen in this photo however, the dip-slip style of faulting can clearly be seen in T5.
29 The second major feature identified by the mapping portion of this survey is a saddle on the north slope of the Punta Banda Ridge near the center of the basin. The overall trace of this feature creates an arc shape starting in front of the highest point on the Punta Banda Ridge, extending westward along the backbone of the ridge, and ending near the beach at La Jolla (Figure 4b). The ABF in this area loses its clear geomorphic expression as a single fault trace and instead is defined as a series of splays. Two possible interpretations explain this feature. This could be a gravitational slide block which faulted into the basin and overrode the ABF. The slide is likely the result of an oversteppened Punta Banda Ridge which is due to the normal component of faulting on the ABF. Continued dextral faulting on the ABF is likely taken up by the series of smaller faults within this block. Given that the tow of the slide block is not Figure 9: Photo looking s outheast along the Punta Banda Ridge. The whit e dashed line represents the trace of the slide block/normal fault and the arrow represents the direction of movement. The ABF in this location is further down the mountain front.
30 exposed, this feature could also be a normal fault which is rooted in the ABF. This feature would also accommodate oversteppening of the Punta Banda Ridge. 4.2 Gravity Survey A total of 382 gravity stations were collected during the summers of 2008 and 2009. The gravity measurements covered the on land area of the Maneadero basin which is approximately 100km2. The survey also extended outside of the basin in order to capture the full gravitational anomaly of the basin. Most importantly, the survey crosses the ABF and up onto the Punta Banda Ridge, which bounds the southern margin of the basin. The gravity stations were 500 m apart in the interior of the basin and shortened to 250m around structurally important areas that have, or potentially could have, steep gravitational gradients (e.g.: Agua Blanca fault, Estero Beach fault). After the gravity corrections were applied to the newly collected data, the anomaly values ranged from -16 to 22 mGals. As mentioned before these values are relative to the absolute gravity station (Hidalgo Statue) in Ensenada, MX. This dataset was combined with existing data that was presented by Perez Florez et al 2004. The combined data yielded a range of anomaly values from -32 to 22 mGals. The combined dataset was color-contoured with a minimum curvature algorithm and displayed over a DEM (Figure 10). First order observations can be easily seen on this map.
31 The lowest gravity values occur near the middle of Bahia Todos Santos identified by the dark blue areas on the Figure 10. Alternatively, the highest values are the reddish-pink areas located on the Punta Banda Ridge and the mountainous region east of Maneadero. As expected, the locations of these low (blue) and high (reddish-pink) areas represent the deepest part of the basin where sediment fill is the thickest and the outcropping rock which forms the boundary of the basin, respectively. The gravity anomaly clearly shows the basin boundary extending from Ensenada to the ABF in the eastern half on the basin. A steep gradient is also present along the ABF. As expected, the gradient closely follows the mapped trace of the ABF in the onshore portion of the Figure 10: DEM overlain with a color-contoured gravity ma p. Notice how the gravity highs closely trace the boundary of the basin where outcropping basement rock exists.
32 study area. This is likely caused by an abrupt change in density from the basin fill to the basement rock that makes up the Punta Banda Ridge. This gradient is not as clear in the offshore segment. In the western portion of the study area there is a slight gradient just north of Isla Todos Santos which could reflect the clockwise rotated segment of the ABF offshore. 4.3 Profile Models In all the profiles the density variations were set before modeling. The basement rock was given a density of 2.66 g/cm3, which was obtained by using the Paranis Method (1976) for bulk density below gravity stations. The basin fill was given a density of 2.0 g/cm3 as mentioned above (see Methods p.25). The profiles which extend into Bahia Todos Santos needed to take into account the water column between the observation point and basin fill. Bathymetry data were provided by Dr. Antonio Gonzalez (personal correspondence) and is included in the models with a density of 1.0 g/cm3. A total of 8 profiles were constructed across the basin. Five of these (Profiles A, B, C, D, and E) are perpendicular (fault-normal) and three (Profiles F, G, and H) are parallel (fault-parallel) to the ABF (Figure 9). Each profile starts and ends outside of the basin to fully capture the geometry of the basin. The locations where basin fill meets outcropping basement rock is identified on the DEM and transferred to each profile. The location of the ABF in the Maneadero Basin is constrained in each profile using structural maps. The onshore trace of the ABF is determined using maps from previous studies and those created as part of this study. The offshore trace of t he fault is determined from seismic surveys conducted in the bay region of the basin (Legg et al., 1991).
33 Profile A (Figure 11) is the eastern most profile in this study and extends from the hillside bounding the east side of the basin to the Punta Banda Ridge passing close to the town of Maneadero. In this model the sediment thickness is shallow (~200m) at its deepest point. The deepest section is inferred from the maximum negative gravity anomaly. The location of this is spatially close (~5-10 km) to the ABF which is modeled here as a steeply north-dipping fault. To the north the basement/basin fill interface rises gradually. The gravity data also does not reflect the location of the Estero Beach fault. Profile B (Figure 11) has a similar trend and is located to the west of Profile A. The sediment thickness increases to about 250m and again is located close (~5-10 km) Figure 11: A DEM image overlaid with the location and extent of the profiles modeled in Maneadero Basin (red lines). The mapped traces of the Estero Beach f ault and the Agua Blanca fault are also overlaid on the map. The solid line marks the observed sections and the dotted lines mark the inferred section of the faults.
34 to the fault. The gradient of the anomaly around the ABF is less steep compared to Profile A. One possible model that fits the observed gradient includes modeling the effect of the slide block as it overrides the trace of the ABF. The north side of the basin is modeled best as a gently sloping surface although it appears to be slightly steeper than Profile A. At the SW end of this profile the calculated gravity values deviates from the observed values, which may have resulted from the oversimplified model presented. Alternatively, this area has significant topographic variation which may not have been completely accounted for in the data reduction process. Profile C (Figure 12) is the next profile west of Profile B. Here the negative magnitude of the anomaly begins to increase due to increased thickness of basin fill, which is about 450m at its deepest. The asymmetrical shape is clear in the profile. Profile D (Figure 12) is an offshore profile and includes the bathymetry of Bahia Todos Santos. This profile crosses the ABF between the tip of Punta Banda and Isla Todos Santos. The magnitude of the anomaly continues to increase as basin fill increases. The fill is about 800m at its deepest. The north side of the basin also is best modeled with an irregularly sloping surface. It is important to note that this profile has the highest error between the model and the gravity anomaly. One reason could be that the gravity anomaly and simplistic model presented here might not account for all the complexities of fault-basin interface in this area. Alternatively, this could have been produced by errors in gravity data corrections for some of the offshore stations. Profile E (Figure 13) is the western most profile. The southern end of the profile crosses the ABF close to where the fault bends clockwise and trends in a more northerly direction. The basin fill begins to thin west of Profile D and is shown here as being only 250m. The basin is also relatively flat and loses much of its asymmetrical shape
35 compared to the other fault-normal profiles. At the southern end of this profile the ABF is not well defined in either the gravity anomaly or the bathymetry in this part of the bay. This might be the result of the ABF transitioning into the Continental Borderlands and therefore losing its geomorphic expression. Profile F (Figure 13) is the southernmost profile that parallels the ABF. Here the profile reveals a relatively symmetrical bowl shaped basin with a depth of about 850m near the middle of the profile. Profile G (Figure 14) is the next profile north from Profile F. The model shows the basin beginning to shallow north from the ABF to about 800m and preserves the symmetrical bowl shaped geometry. The ABF is inferred to be located west of the gravity survey and therefore is not present in the last two profiles. Profile H (Figure 14) is the northernmost fault-parallel profile for this study. The model again continues to shallow to about 400m as well as preserves the symmetrical basin geometry. Overall, the profiles show an asymmetric basin shape. The deepest section of the basin is located offshore in Bahia Todos Santos. A maximum depth of approximately 900 m below mean sea level (b.m.s.l) is illustrated in Profile F. In the fault-normal oriented profiles the deepest parts of the basin are spatially closer to the ABF. As a result the south side of the basin shallows steeply against the ABF as opposed to the north side which shallows more gradually. The south side of the basin is truncated by the ABF which is modeled as a steeply northward dipping fault. This is best shown in Profiles A-D. The fault-parallel profiles show a more symmetrical basin geometry that gradually shallows to the east and west from the deepest section of the basin. This is best shown in Profiles G and H (Figure 13). To insure that these 2.5-D
36 models are reasonable in a 3-D setting, the basin depths at intersection points were compared and found to closely match (+ 5 m). Therefore, a 3-D model of the Maneadero Basin could be constructed from the 2.5-D models. This was accomplished by plotting and contouring the basement depths along each profile (Figure 15).
37 Figure 12: Profile A oriented NE-SW and is the eastern most profile of the Maneadero Basin. Due to its close proximety to the basin boundary sediment fill is onl y about 200m at it deepest point. There is also a sharp break in basement slope on the south side of the basin which is interpreted as the location of the A gua Blanca fault. The fault is modeled as a steeply northward dipping structure. Profile B has the same orientation and is the next model west of Profile A. This profile contains the slump block that was mapped on the north side of Punta Banda. This slump block was most likely the result of an oversteeping of the ridge. The slump likely crossed the ABF and was subsequentl y cut by continued dextral faulting of the ABF. The model to the SW of the ABF begins to deviate from the observed values which might result fr om an oversimplification of the model.
38 Figure 13: Profile C has a NE-SW orientation and is the next profile west of Profile B. Here the basin geometry is more similar to that of Profile A. The ABF in this gravity profile is best modeled as a steeply north dipping fault. Profile D is the next profile as one moves west from Profile C. It also has the NE-SW orientation. This profile has the highest error of all the profiles. Notice the lack of change in the gravity signal around the ABF. It is unclear as to why the gravit y anomoly remains flat here. An error in the collection or reduction of the gravity data around the section of the marine survey could explain this oddity which closely reflects the bathymetr y The rest of the basin is modeled with a high degree of accuracy up to the ABF.
39 Figure 14: Profile E is the western-most NE-SW profile. The gravity anomoly along this line is mostly flat with little fluctuation. This suggest a shallow basin with vary little thick ness variations. This is confirmed b y the best fit forward model shown. The location of t he ABF is difficult to pinpoi nt looking at the gravit y profile. This area has been characterized as an immensily complex area where the ABf meets the Continental Borderlands. The inferred trace of the ABF along this profile shows a small perturbation in the gravity anomoly. This very low amplitude signal might be the location of the ABF. It is important to note that the fault can shift 1-2km north or south from its present location without changing the error of the model. Profile F is the first of three profiles that are modeled in a NW-SE orientation that closel y parallels the ABF. This model fits the observed val ues very well throughout the entire profile. The ABF is more clearly seen in the gravity anomaly as opposed to Profile E however, the location of the fault can be moved about 1km north or south without changing the models error.
40 Figure 15: Profile G is the next profile to the north of Profile F and shares a similar orientation. The model is well constrained with the observed values as indicated by the low error. At the far western end the model does not intersect the ABF because the infe rred trace is outside of the marine survey area therefore could not be modeled with any certainty. However, basin geometry to the edge of the surve y area is reflected by the model. Profile H extends across the northern section of t he basin in a NW-SE orientation. Again, the location of the ABF is outside of the marine survey area and therefore is not included in the model. This profile has the lowest error of any model created which suggests the model is well constrained to the observed values.
41 Figure 16: A contour map of basin depths as determined from the forward profile models. Contours are in meters relative to sea level. Faults within the st udy area are marked with solid lines where observed and dashed lines where inferred. Again, the deepest parts of t he basin is centered over the lowest values in the study area. The outlne of the basin is can also be seen.
42 Chapter 5 Discussion It has been suggested that the Maneadero Basin is within a step-over and that the basins formation is due to a right step in the dextral ABF (Gastil, 1975; Schug, 1987; Legg et al., 1991). This is an odd interpretation given that other faults with similar orientations within the San Andreas System tend to be characterized as accommodating contraction (e.g. Puente Hills Fault; Dolan et al., 2003). Three hypotheses have been proposed to explain the existence of the Maneadero Basin. The combined geophysical and structural datasets presented here are used to test these three competing hypotheses. Hypothesis 1: The Maneadero Basin is formed solely by a dip-slip component on the ABF and is truly a transtensional structure as suggested by previous studies. A basin formed by a dip-slip component on the ABF would form an asymmetrical basin in both the vertical and horizontal perspectives with the long axis paralleling the ABF and the deepest part located against the fault. From this deep section the basin would gradually shallow to the north and east, and eventually basement outcrop would mark the basin boundary (Figure 3a). The gravity anomaly would also reflect this geometry with a steep gravity gradient around the ABF and shallower gradient to the north and east.
43 This generally hypothesis is supported by the data presented in this study. The gravitational anomaly shows a steep gradient with a magnitude of about 40 mGals which follows the trace of the ABF and a less steep gradient to the north. Best fit models of the anomaly yield a basin geometry that closel y resembles the type of geometry expected given the structural scenario presented (Figure 3a). This is best illustrated in Profile A, B, and C. Here the deepest parts of the basin are spatially close to the ABF and gradually thin to the north. Structural observations also support the possibility of a dip-slip component of motion on the ABF. The uplifted fluvial terraces at Las Animas and the marine terraces at Punta Banda record a normal component of slip on the ABF that is concurrent with the more obvious dextral faulting (Schug, 1987; Rockwell et al., 1987). The presence of a slide block/rooted normal fault near the center part of the basin suggests that the Punta Banda Ridge has been over-steepened as a result of uplift. The location of this slide block/normal fault correlates well with the area of the ABF that is characterized by several fault splays rather than a single feature. This feature is likely overprinting the expression of dextral faulting on the ABF, which could explain the observation of multiple branches along the ABF at this location. These branches likely accommodate dextral faulting as the ABF attempts to cut through the slide block/normal fault. Hypothesis 2: The Maneadero Basin formed at a right step in the dextral ABF. A basin formed in a right step in the ABF would form an asymmetrical basin in map view with the long axis parallel to the ABF. The deep part of the basin would likely be centered between the overlapping fault strands as illustrated in the second block model (Figure 3b). The north and south boundaries of the basin would be fairly steep and would be defined by almost pure strike-slip deformation. The southeastern and
44 northwestern boundaries should be defined by normal dip-slip faults as dextral faulting around the step-over drives extension in the intervening area (Nilsen and Slyvester, 1995). The gravity anomaly associated with this type of basin formation would most likely have a parabolic and symmetrical shape in both the fault-normal and fault parallel directions (Gibson et al., 1994; Garfunkle and Ben-Avraham, 1996). This hypothesis is not supported by the gravity data. The negative anomaly, which reflects the deepest part of the basin, is spatially close to the ABF and is off center from the basin. Also, the gradients on the north and south side have different slopes. Previous studies have suggested that the Estero Beach fault to the north might be a step-over in the ABF (Legg et al., 1991). The results of the survey also show no evidence of a major fault on the north side of the basin that is commensurate with a step-over including the Estero Beach fault. Structurally, the location of the Estero Beach Fault rules it out as a potential step-over. Its mapped trace cuts through the middle of the basin and comes spatially close to the deepest part of the basin where the lowest gravity values are located. This arrangement is not consistent with basin formation at a step-over (Nilsen and Sylvester, 1995). The trace of the fault is also inferred to extend ~30-50 km east from the Maneadero basin past Valle Santo Toms (mapping by Wetmore, personal communication, 2009). This arrangement is also inconsistent with a step-over structures that only overlaps where the basin is located. Geomorphic observations do not support the second hypothesis either. Evidence of recent faulting is limited to an aquitard effect found along the trace of the Estero Beach fault and a seismic swarm of micro-quakes in May of 1981 (Gonzalez-Suarez et al., 1984). There are no scarps in the topography or bathymetry around the Estero Beach Fault suggesting that either faulting is too recent or a slow rate of offset occurs on this fault. Both cases minimize or possibly preclude the possibility that this fault acts as a major
45 step-over to the ABF thereby causing the formation of a pull-apart structure (Figure 13). Furthermore, if the basin formed at a step-over then there should be a normal fault bounding the southeastern and northwestern sides of the basin. The eastern edge of the Maneadero Basin is located near the town of Maneadero and no evidence of normal faulting is observed in this area in either the mapping or the gravity data. Hypothesis 3: The Maneadero Basin formed as a result of juxtaposing topographically high mountains with deeper parts of the continental borderlands. A basin formed under this condition would form an asymmetrical basin with the long axis perpendicular to the ABF. The deepest part of the basin would be on the western edge and would gradually shallow to the east. The gravity anomaly associated with this type of basin geometry would have a low value in the west and gradually increasing to the east where the basement outcrops east of the city of Maneadero. This hypothesis is supported by the data presented here. While the simplified block model does not match the gravity data exactly, the idea of juxtaposing topographically higher areas with lower ones as a means of creating space for basin formation still has merit for the Maneadero Basin. Profiles F, G, and H all show a roughly symmetrical, bowl-shaped gravity ano maly and the models also reflect this shape. This bowl feature, which is now partially filled with sediments, is most likely an erosional feature. Multiple drainages flow into Bahia Todos Santos from the mountains to the north, east and southeast and during low sea stands those all drained out through the canyon between Punta Banda and Isla Todo Santos. The present-day bathymetric deep on Bahia Todo Santos presently resides adjacent to the canyon between Punta Banda and Isla Todos Santos (Figure 13). The deepest part of the basement (i.e. the lowest elevation of the contact between the basement and overlying sediments) is
46 presently offset from the canyon by ~7 km (Figure 16). Thus, the dextral slip along the ABF has juxtaposed the topographically higher Punta Banda Ridge with this topographic depression. The gravitational and structural data presented here shows the Maneadero Basin likely formed as a result of multiple processes. A dip-slip component on the ABF and the juxtaposition of topographically higher areas with lower areas work in concert to drive Figure 17: Bathymetric map of Bahia Todos Sa ntos notice the bowl shaped depression located between the tip of Punta Banda and Isla Todos Santos. This is likely a erosional freature that resulted from drainage off the pennisula being funneled through this area.
47 basin subsidence and create space for sediment fill. Interestingly, the western reach of normal displacement in Valle Santo Toms corresponds with the eastern reach of normal displacement on the ABF to the north in Valle Maneadero suggesting these two faults are working in concert to accommodate the extension in the region (Fletcher, personal correspondence). In the Maneadero Basin the amount of normal displacement in Las Animas is greatly reduced both in rate and total offset when compared to the marine-terraces on the western edge of the Punta Banda Ridge. This suggests that the orientation of the ABF relative to the Baja microplate motion is creating a transtensional regime in the area of the Valle Maneadero and thus driving basin subsidence. Therefore, the basin formation is most likely the combined result of transtension and strike-slip juxtaposition of different topographies.
48 Chapter 6 Conclusions Structural and geophysical data suggests that the Maneadero Basin is formed by transtension and strike-slip juxtaposition of the topographically high Punta Banda Ridge with a lower erosional feature. The strike-slip component of the basins form ation is illustrated by juxtaposing the Punta Banda ridge with an deep (~900m) bowl shaped erosional feature in Bahia Todos Santos. This feature is likely the result of the bay acting as a major spillway for muiltiple fluvial drainages off of the adjacent peninsula. Dextral slip has place the uplifted Punta Banda Ridge next to this erosional depression. Modeling of gravity data clearly illustra tes that the geometry of the Maneadero Basin closely resembles one which would form by a strong normal component on the ABF. This transtension is likely the result of the orientation of the ABF relative to the motion of the Baja microplate. Where the ABF is in better alignment with the Baja microplate motion there is little to no transtension as shown by the geomorphic expression in places like Valle Trindad and Valle Agua Blanca. As the fault rotates clockwise and becomes more oblique to the microplate motion a component of normal slip is present as is the case with Valle Santo Thomas and Valle Maneadero.
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60 Appendix A: Collected Gravity Data and Corrections The appendix presented here contains the stations collected for this survey. Each station includes the following characteristics: Machine used to collect the gravity measurement Station location which includes the latitude, longitude, and elevation as determined from the differential GPS system mentioned in the Methods sections. Observed gravity DC shift to 2008 dataset. This is the yearly drift correction which was applied to the 2009 dataset in order to make one cohesive dataset. Value of the corrections applied to the observed gravity which includes tidal correction, drift correction, free air correction, latitude correction, Bullard A correction, Bullard B correction, Bullard C correction. The complete Bouguer gravity value. There are several fields that do not contain numbers. Fields that have an asterisk (*) represent a blank value. This is applicable to only the 2008 dataset. The carat (^) represents a blank value also because the ZLS gravity meter reported observed gravity values that were tidal corrected. Therefore, no additional calculation was required for this correction. A digital copy of this data is included on the CD which accompanies this thesis.
61 Appendix A: (Continued) Sta #Inst. Lat ('s N)Long ('s W) Elev (m)Obs Grav (mGal)DC shift '08TidecorrDriftcorr FAcorrLATcorrBullABullBBullCBc Grav (mGal) 4L&R31.718 116.6700.5742806.717*0.1600.035 4.82815.7911.7450.023 0.7522818.820 5L&R31.718 116.6661.7082805.085 *0.1600.049 4.47815.7971.6180.021 0.6812817.473 6L&R31.719 116.6611.7412801.051 *0.1600.060 4.46815.7051.6150.021 0.7322813.292 7L&R31.722 116.6561.0892794.692 *0.1500.083 4.66915.5021.6870.022 0.7302806.570 8L&R31.725 116.6521.1702790.937 *0.1400.096 4.64515.2621.6780.022 0.6942802.604 9L&R31.728 116.6480.8362789.024 *0.1250.109 4.74814.9951.7150.023 0.6922800.334 10L&R31.732 116.6451.1112787.850 *0.1150.122 4.66314.6991.6850.022 0.7372798.850 11L&R31.735 116.6421.0352787.464 *0.1000.134 4.68614.3991.6930.022 0.7062798.152 12L&R31.739 116.6401.0002787.025 *0.0900.147 4.69714.0771.6970.022 0.7242797.343 13L&R31.775 116.6232.6752793.502 0.0250.236 4.18011.1861.5100.020 0.7312801.047 14L&R31.771 116.6262.6642792.144 0.0420.256 4.18311.5041.5120.020 0.7102799.988 15L&R31.767 116.6272.3852791.103 0.0500.266 4.27011.8431.5430.020 0.7112799.213 16L&R31.763 116.6292.5842790.386 0.0590.275 4.20812.2051.5210.020 0.7402798.850 17L&R31.759 116.6302.8592789.412 0.0670.287 4.12312.5041.4900.020 0.7022798.246 18L&R31.755 116.6322.8992788.644 0.0700.297 4.11112.8541.4850.019 0.7132797.813 19L&R31.750 116.6342.8762787.941 *0.0720.305 4.11813.2021.4880.020 0.7242797.575 20L&R31.747 116.6352.8662787.632 0.0800.312 4.12113.4451.4890.020 0.6952797.377 21ZLS31.743 116.6372.8042787.413 0.0800.324 4.14013.7501.4960.020 0.7332797.402 23ZLS31.715 116.67327.0372805.914 ^ 0.0133.33816.021 1.206 0.016 0.7052823.359 24ZLS31.714 116.67544.6442802.848 ^ 0.0198.77216.120 3.169 0.042 0.7422823.805 25ZLS31.713 116.67661.5802799.961 ^ 0.02013.99816.200 5.058 0.066 0.7612824.294 26ZLS31.712 116.67883.8702795.662 ^ 0.02220.87716.284 7.543 0.099 0.7012824.502 27ZLS31.711 116.679102.1052792.017 ^ 0.02526.50416.363 9.577 0.126 0.7192824.488 28ZLS31.711 116.681134.3312785.293 ^ 0.02736.44916.367 13.170 0.173 0.7262824.067 29ZLS31.712 116.684173.9762777.793 ^ 0.02948.68316.282 17.591 0.231 0.7062824.260 30ZLS31.711 116.685167.8942779.786 ^ 0.03146.80616.414 16.913 0.222 0.7082825.194 31ZLS31.709 116.687138.2662785.648 ^ 0.03337.66316.523 13.609 0.179 0.7452825.335 32ZLS31.706 116.68745.9342804.764 ^ 0.0369.17016.804 3.313 0.043 0.7552826.661 33ZLS31.679 116.588162.2082761.377 ^ 0.00445.05218.961 16.279 0.214 0.7112808.190 34ZLS31.683 116.589108.1712772.525 ^ 0.00428.37618.643 10.253 0.135 0.7302808.431 35ZLS31.689 116.59060.0672782.770 ^ 0.00513.53118.178 4.889 0.064 0.7312808.801 36ZLS31.694 116.59143.1782786.657 ^ 0.0068.31917.768 3.006 0.039 0.7222808.982 37ZLS31.699 116.59238.8042787.848 ^ 0.006 6.96917.308 2.518 0.033 0.7332808.847 38ZLS31.704 116.59321.1712791.465 ^ 0.0071.52816.915 0.552 0.007 0.7472808.609 39ZLS31.709 116.59419.2532791.516 ^ 0.0080.93616.551 0.338 0.004 0.7172807.951 40ZLS31.713 116.59518.6792791.755 ^ 0.0080.75916.200 0.274 0.004 0.7012807.744 41ZLS31.718 116.59615.4552792.778 ^ 0.008 0.23615.8170.0850.001 0.7252807.729 42ZLS31.723 116.59713.0072793.445 ^ 0.009 0.99215.4200.3580.005 0.7282807.517 43ZLS31.728 116.59811.7172794.156 ^ 0.009 1.39015.0300.5020.007 0.7492807.566 44ZLS31.733 116.5998.3662793.793 ^ 0.011 2.42414.5740.8760.011 0.6882806.154 45ZLS31.738 116.6006.7942793.299 ^ 0.012 2.90914.1931.0510.014 0.7142804.946 46ZLS31.743 116.6016.7402793.189 ^ 0.012 2.92613.7981.0570.014 0.7242804.421 47ZLS31.748 116.6026.8132793.557 ^ 0.007 2.90313.3511.0490.014 0.7 532804.322 48ZLS31.754 116.6036.3012794.190 ^ 0.009 3.06112.9241.1060.015 0.7232804.460 49ZLS31.756 116.6036.5302794.414 ^ 0.012 2.99012.7381.0800.014 0.7412804.526 50ZLS31.745 116.58413.1362794.916 ^ 0.016 0.95213.6390.3440.005 0.6962807.271 51ZLS31.740 116.58311.6292795.704 ^ 0.022 1.41714.0380.5120.007 0.6942808.172 52ZLS31.734 116.58214.8682795.340 ^ 0.024 0.41714.5020.1510.002 0.6892808.912 53ZLS31.730 116.58116.5312795.250 ^ 0.0270.09614.861 0.0350.000 0.7092809.490 54ZLS31.724 116.58020.2492796.078 ^ 0.0291.24315.270 0.449 0.006 0.7172811.448 55ZLS31.720 116.57921.9772794.177 ^ 0.0341.77715.635 0.642 0.008 0.7522810.220 56ZLS31.715 116.57824.9012794.923 ^ 0.0362.67916.043 0.968 0.013 0.7592811.941 57ZLS31.710 116.57727.9822794.877 ^ 0.0383.63016.441 1.312 0.017 0.7502812.907 58ZLS31.705 1 16.57630.6292795.367 ^ 0.0404.44716.819 1.607 0.021 0.7202814.325 59ZLS31.700 116.57534.6152794.365 ^ 0.0435.67717.226 2.051 0.027 0.7202814.513 60ZLS31.695 116.57449.2352790.922 ^ 0.04410.18817.661 3.681 0.048 0.6882814.397 61ZLS31.690 116.57355.5372787.780 ^ 0.04612.13318.037 4.384 0.058 0.7262812.828 62ZLS31.685 116.57278.7002781.281 ^ 0.04819.28118.461 6.967 0.091 0.7532811.261 63ZLS31.681 116.571102.0332775.471 ^ 0.05226.48218.750 9.569 0.126 0.7032810.358 64L&R31.692 116.649364.6322734.442 0.0600.585107.52017.929 38.850 0.510 0.7672819.118 65L&R31.692 116.644328.1062739.154 0.0600.65496.24817.907 34.778 0.457 0.7412816.619 66L&R31.690 116.640321.9952739.581 0.0600.67694.36218.059 34.096 0.448 0.7572815.966 67L&R31.687 116.637298.0242744.201 0.0 600.69886.96518.304 31.423 0.413 0.7282816.148 68L&R31.684 116.633227.8322757.038 0.0500.71865.30418.533 23.596 0.310 0.7562815.445 69L&R31.657 116.573551.5232685.612 *0.140 0.059165.19520.707 59.690 0.784 0.7412810.498 70L&R31.658 116.572464.6342703.382 *0.140 0.079138.38020.613 50.001 0.656 0.7812811.154 71L&R31.659 116.570408.1832714.840 *0.140 0.087120.96020.563 43.707 0.574 0.7222811.588 72L&R31.661 116.570361.7662724.167 *0.130 0.095106.63620.432 38.531 0.506 0.7252811.698 73L&R31.662 116.570362.1072723.957 *0.128 0.104106.74120.288 38.569 0.506 0.7172811.425
62 74L&R31.664 116.571349.1752726.178*0.114 0.115102.75020.167 37.127 0.487 0.7232810.986 75L&R31.666 116.569290.5262736.568 *0.110 0.12184.65119.988 30.587 0.402 0.7482809.701 76L&R31.668 116.569249.4552744.444 *0.100 0.12871.97619.819 26.007 0.341 0.7082809.410 77L&R31.671 116.569203.2382753.821 *0.094 0.13357.71419.622 20.854 0.274 0.7112809.545 78ZLS31.673 116.569160.4722762.137 ^0.01344.51619.395 16.085 0.211 0.7522808.987 79ZLS31.676 116.570141.9582766.380 ^0.01738.80319.184 14.021 0.184 0.7352809.410 80ZLS31.679 116.570121.5872769.172 ^0.02332.51618.980 11.749 0.154 0.7312808.011 81ZLS31.682 116.619122.0652772.756 ^0.04032.66418.719 11.803 0.155 0.7352811.407 82ZLS31.685 116.61982.6022779.879 ^0.05120.48518.507 7.402 0.097 0.7192810.601 83ZLS31.687 116.62059.7852783.239 ^0.05313.44418.302 4.858 0.064 0.7152809.296 84ZLS31.690 116.62143.2252785.250 ^0.0588.33418.096 3.011 0.040 0.7102807.861 85ZLS31.692 116.62121.0522788.251 ^0.0611.49117.872 0.539 0.007 0.7602806.247 86ZLS31.697 116.62213.9702788.646 ^0.065 0.69417.4700.2510.003 0.7602804.851 87ZLS31.702 116.62310.8652788.841 ^0.068 1.65217.1060.5970.008 0.7252804.107 88ZLS31.707 116.6248.6462789.043 ^0.073 2.33716.7090.8450.011 0.7332803.464 89ZLS31.711 116.6255.6752789.349 ^0.076 3.25416.3801.1760.015 0.7422802.849 90L&R31.671 116.615439.4742713.946 *0.132 0.181130.61619.628 47.196 0.620 0.7262815.962 91L&R31.672 116.615417.6002716.153 *0.140 0.218123.86619.505 44.757 0.588 0.7322813.805 92L&R31.674 116.614375.1692725.478 *0.150 0.244110.77219.338 40.025 0.525 0.7672814.664 93L&R31.676 116.614333.3822732.379 *0.150 0.26897.87619.186 35.366 0.464 0.7442813.285 94L&R31.677 116.613288.2982741.150 *0.150 0.29483.96319.079 30.339 0.398 0.7742813.126 95L&R31.679 116.611209.1182756.115 *0.150 0.322 59.52818.948 21.509 0.282 0.7762812.496 96L&R31.681 116.609138.7722769.529 *0.143 0.35637.81918.818 13.665 0.179 0.7012812.120 97L&R31.692 116.62537.3382790.607 *0.045 0.5626.51717.897 2.355 0.031 0.7062812.536 98L&R31.693 116.62021.4742791.292 *0.035 0.5901.62117.834 0.586 0.008 0.7112810.068 99L&R31.694 116.61526.4542786.981 *0.022 0.6083.15817.776 1.141 0.015 0.7272806.662 100L&R31.694 116.61031.2632785.853 *0.010 0.6264.64217.711 1.677 0.022 0.7262806.417 101L&R31.695 116.60433.1062785.749 *0.000 0.6405.21117.641 1.883 0.025 0.7272806.607 102L&R31.696 116.59735.3782787.170 0.002 0.6555.91217.564 2.136 0.028 0.7192808.416 103L&R31.697 116.59240.3342788.040 0.050 0.7407.44217.494 2.689 0.035 0.7142810.228 104L&R31.698 116.58544.7202789.580 0.051 0.7528.79517.419 3.178 0.042 0.7092812.567 105L&R31.699 116.58034.8562797.372 0.060 0.7715.75117.350 2.078 0.027 0.7082818.372 106L&R31.700 116.57438.5732793.985 0.060 0.7806.89817.287 2.492 0.033 0.7152815.649 107L&R31.700 116.56937.2282794.267 0.061 0.7936.48317.219 2.343 0.031 0.7182815.610 P01ZLS31.681 116.606122.2132768.254 ^0.01232.70918.796 11.819 0.155 0.7442807.030 P02ZLS31.684 116.60693.3022773.398 ^0.01723.78818.568 8.595 0.113 0.7142806.315 P03ZLS31.687 116.60766.6892778.043 ^0.02015.57518.342 5.628 0.074 0.7662805.473 P04ZLS31.690 116.60744.5312781.671 ^0.0238.73718.061 3.157 0.041 0.7452804.502 P05ZLS31.694 116.60831.4552784.388 ^0.0284.70217.739 1.699 0.022 0.6912804.389 P06ZLS31.700 116.61025.2612785.443 ^0.0302.79017.279 1.008 0.013 0.6972803.763 P07ZLS31.704 116.61018.7002786.992 ^0.0340.76516.904 0.277 0.004 0.7322803.616 P08ZLS31.709 116.61119.9482787.032 ^0.0371.15116.528 0.416 0.005 0.6852803.567 P09ZLS31.714 116.61211.6632789.099 ^0.040 1.40616.1320.5080.007 0.6982803.601 P10ZLS31.719 116.6139.4002790.097 ^0.047 2.10515.7080.7600.010 0.7492803.675 P11ZLS31.724 116.6147.5272790.687 ^0.050 2.68315.3270.9690.013 0.6952803.568 P12ZLS31.729 116.6156.7822790.784 ^0.054 2.91314.9321.0520.014 0.7062803.110 P13ZLS31.730 116.6214.1392790.090 ^0.058 3.72814.8311.3470.018 0.7412801.758 P14ZLS31.721 116.6226.2802789.398 ^0.065 3.06815.5861.1080.015 0.6882802.287 P15ZLS31.664 116.533101.0682774.452 ^0.10526.18420.137 9.461 0.124 0.7412810.342 P16ZLS31.667 116.53690.8162776.405 ^0.10823.02019.898 8.318 0.109 0.7072810.081 P17ZLS31.671 116.53978.7322778.777 ^0.11419.29119.622 6.971 0.092 0.7022809.812 P18ZLS31.673 116.54472.3562779.940 ^0.13217.32419.390 6.260 0.082 0.7392809.441 P19ZLS31.676 116.54985.7482778.095 ^0.13721.45619.178 7.753 0.102 0.7272810.011 P20ZLS31.679 116.55383.1112779.602 ^0.14020.64318.904 7.459 0.098 0.7202810.731 P21ZLS31.685 116.55667.3202783.997 ^0.14315.76918.495 5.698 0.075 0.7112811.635 P22ZLS31.687 116.56468.9022783.697 ^0.14916.25818.281 5.874 0.077 0.7042811.431 P23ZLS31.693 116.56552.6392787.721 ^0.15311.23917.836 4.061 0.053 0.7302811.799 P24ZLS31.698 116.56638.9662791.549 ^0.1587.01917.407 2.536 0.033 0.7022812.546 P25ZLS31.703 116.56638.2162793.689 ^0.1616.78817.015 2.453 0.032 0.7162814.130 P26ZLS31.704 116.55768.4972786.870 ^0.16716.13316.886 5.829 0.077 0.7282813.088 P27ZLS31.707 116.55470.3462785.728 ^0.16916.70316.641 6.035 0.079 0.7572812.031 P28ZLS31.713 116.55477.3072784.809 ^0.17418.85116.159 6.812 0.089 0.7462811.997 P29ZLS31.717 116.55483.2422784.718 ^0.17820.68315.864 7.473 0.098 0.7182812.797 P30ZLS31.721 116.55699.2242781.194 ^0.18325.61515.507 9.256 0.122 0.6972812.060 P31ZLS31.726 116.55687.6892783.795 ^0.18722.05515.148 7.969 0.105 0.7402811.997 P32ZLS31.731 116.55798.0222782.086 ^0.19125.24414.748 9.121 0.120 0.7472811.899 P33ZLS31.736 116.557124.8962776.871 ^0.19533.53714.343 12.118 0.159 0.7392811.540 P34ZLS31.740 116.560108.0002780.762 ^0.20128.32314.022 10.234 0.134 0.6892811.849 P35ZLS31.743 116.56449.5222790.313 ^0.20510.27713.793 3.713 0.049 0.7232809.693 108L&R31.669 116.594440.6172704.988 *0.1050.076130.96919.745 47.323 0.621 0.7832807.003 Appendix A: (Continued)
63 Appendix A: (Continued) 109L&R31.671 116.592371.9202718.277*0.1200.094109.76919.619 39.663 0.521 0.7182806.790 110L&R31.672 116.591323.9652727.382 *0.1300.10794.97019.537 34.316 0.450 0.7672806.378 111L&R31.674 116.590262.9382739.719 *0.1400.12076.13719.385 27.511 0.361 0.7392806.651 112L&R31.675 116.590233.6582745.862 *0.1500.13667.10119.264 24.246 0.318 0.7572806.920 113L&R31.676 116.590207.6192751.496 *0.1520.14359.06619.154 21.342 0.280 0.7052807.398 114L&R31.681 116.589133.2082767.192 *0.1300.15336.10318.812 13.045 0.171 0.6952808.173 115ZLS31.741 116.6144.1222791.412 ^0.023 3.73313.9811.3490.018 0.6962802.307 116ZLS31.741 116.6084.6712792.163 ^0.023 3.56413.9131.2880.017 0.6952803.098 117ZLS31.743 116.5967.7752793.147 ^0.024 2.60613.7750.9420.012 0.6952804.550 118ZLS31.744 116.5919.2042793.759 ^0.024 2.16513.6980.7820.010 0.6882805.372 119ZLS31.745 116.58511.4532794.551 ^0.025 1.47113.6340.5320.007 0.6962806.532 120ZLS31.746 116.57815.1532795.164 ^0.025 0.32913.5580.1190.002 0.6872807.801 121ZLS31.746 116.57316.9492795.803 ^0.0260.22513.497 0.081 0.001 0.6942808.722 122ZLS31.747 116.56720.1162796.819 ^0.0261.20213.418 0.434 0.006 0.6872810.286 123ZLS31.748 116.56226.3442796.248 ^0.0273.12413.344 1.129 0.015 0.7502810.796 124ZLS31.749 116.55637.1182794.982 ^0.0276.44913.292 2.330 0.031 0.6862811.649 125ZLS31.758 116.6094.7542793.206 ^0.003 3.53812.6051.2790.017 0.7442802.821 126ZLS31.759 116.6094.2352793.472 ^0.005 3.69912.4711.3360.018 0.7412802.852 127ZLS31.761 116.6085.4682793.936 ^0.006 3.31812.3401.1990.016 0.7502803.418 128ZLS31.763 116.6084.1662794.288 ^0.007 3.72012.1741.3440.018 0.7102803.387 129ZLS31.764 116.6075.3122794.668 ^0.007 3.36612.0611.2160.016 0.7342803.853 130ZLS31.766 116.6075.1212794.918 ^0.008 3.42511.9441.2380.016 0.7602803.922 131ZLS31.768 116.6073.9092795.259 ^0.017 3.79911.7981.3730.018 0.7452803.886 132ZLS31.769 116.6074.5752795.593 ^0.018 3.59411.6541.2980.017 0.7312804.220 133ZLS31.771 116.6084.7612795.795 ^0.018 3.53611.5001.2780.017 0.7132804.322 134ZLS31.773 116.6084.0272796.300 ^0.019 3.76311.3471.3600.018 0.6952804.548 135ZLS31.775 1 16.6074.3452796.553 ^0.022 3.66511.2091.3240.017 0.6932804.724 136ZLS31.777 116.6054.5092797.025 ^0.023 3.61411.0461.3060.017 0.7292805.027 137ZLS31.780 116.60419.6332794.302 ^0.0241.05310.788 0.381 0.005 0.7472804.987 138ZLS31.782 116.60419.6942794.459 ^0.0251.07210.631 0.387 0.005 0.7202805.024 139ZLS31.784 116.60518.7962794.993 ^0.0260.79510.427 0.287 0.004 0.7172805.181 140ZLS31.786 116.60517.4882795.480 ^0.0260.39110.268 0.141 0.002 0.6932805.277 141ZLS31.790 116.60616.3122796.117 ^0.0270.02810.016 0.0100.000 0.7112805.413 142ZLS31.783 116.59135.2542794.938 ^0.0355.87410.531 2.122 0.028 0.6902808.468 143ZLS31.782 116.59135.6052794.577 ^0.0365.98210.663 2.162 0.028 0.6872808.310 144ZLS31.779 116.59136.5412794.347 ^0.0376.27110.838 2.266 0.030 0.7292808.395 145ZLS31.776 116.59038.4352793.751 ^0.0376.85611.070 2.477 0.033 0.6942808.436 146ZLS31.775 116.59039.1152793.302 ^0.0387.06511.199 2.553 0.034 0.7552808.187 14 7ZLS31.772 116.58913.8352798.586 ^0.039 0.73611.4540.2660.003 0.7422808.792 148ZLS31.770 116.58915.0512798.428 ^0.040 0.36111.5740.1300.002 0.7242809.010 149ZLS31.768 116.58815.6372797.963 ^0.040 0.18011.7420.0650.001 0.6912808.859 150ZLS31.766 116.58816.4082797.446 ^0.0410.05811.933 0.0210.000 0.7502808.624 151ZLS31.763 116.58817.1132797.138 ^0.0410.27612.123 0.100 0.001 0.7352808.660 152ZLS31.759 116.58716.8492796.442 ^0.0420.19412.498 0.070 0.001 0.7022808.319 153ZLS31.754 116.58615.8262795.486 ^0.043 0.12212.9010.0440.001 0.7002807.567 154ZLS31.749 116.58516.0152794.459 ^0.044 0.06313.3110.0230.000 0.7062806.980 168ZLS31.830 116.6104.5352808.465 ^0.060 3.6066.7331.3030.017 0.7252812.128 167ZLS31.826 116.6094.3932808.867 ^0.061 3.6507.0971.3190.017 0.6812812.908 166BZLS31.821 116.6094.2842807.590 ^0.062 3.6837.4611.3310.017 0.7082811.946 165BZLS31.816 116.6094.6752805.916 ^0.063 3.5637.8451.2870.017 0.6912810.748 164BZLS31.812 116.6104.0682804.115 ^0.063 3.7508.2251.3550.018 0.7402809.159 163BZLS31.807 116.6113.8132802.892 ^0.065 3.8298.5991.3830.018 0.7022808.298 162BZLS31.804 116.6114.1192801.840 ^0.066 3.7348.8751.3490.018 0.7152807.567 161BZLS31.800 116.6124.2032800.498 ^0.067 3.7089.2041.3400.018 0.7072806.578 160BZLS31.796 116.6134.0272799.318 ^0.068 3.7639.5231.3600.018 0.6832805.705 159BZLS31.793 116.6143.9462798.570 ^0.069 3.7889.7551.3690.018 0.7142805.141 158BZLS31.790 116.6163.9732797.856 ^0.070 3.7799.9881.3660.018 0.7522804.626 169ZLS31.659 116.53294.4042774.831 ^ 0.00124.12820.582 8.718 0.114 0.7072810.001 170ZLS31.656 116.53497.7192773.350 ^ 0.00125.15120.780 9.088 0.119 0.7102809.365 171ZLS31.653 116.533101.8742771.486 ^ 0.00126.43321.031 9.551 0.125 0.7002808.575 172ZLS31.651 116.532108.4042769.727 ^ 0.00128.44821.163 10.279 0.135 0.6932808.233 173ZLS31.650 116.530105.8322769.768 ^ 0.00127.65421.250 9.992 0.131 0.7112807.839 174ZLS31.649 116.528108.5812769.299 ^ 0.00128.50321.335 10.299 0.135 0.7352807.969 175ZLS31.648 116.527110.6132768.760 ^ 0.00129.13021.422 10.525 0.138 0.6912807.959 176ZLS31.647 116.525113.7272768.208 ^ 0.00230.09121.532 10.873 0.143 0.7302808.087 177ZLS31.645 116.523115.7352767.637 ^ 0.00230.71021.639 11.097 0.146 0.7022808.044 178ZLS31.644 116.522119.5062767.208 ^ 0.00231.87421.745 11.517 0.151 0.7382808.422 179ZLS31.643 116.519129.1242766.391 ^ 0.00234.84221.814 12.590 0.165 0.7462809.548 180ZLS31.778 116.57350.0762794.047 ^ 0.00310.44810.934 3.775 0.050 0.6862810.921 181ZLS31.776 116.57349.9322793.591 ^ 0.00310.40311.080 3.759 0.049 0.6972810.571
64 Appendix A: (Continued) 182ZLS31.774 116.57352.5442792.778*^ 0.00311.21011.258 4.050 0.053 0.7422810.403 183ZLS31.772 116.57253.8852792.011 ^ 0.00311.62411.424 4.200 0.055 0.7122810.094 184ZLS31.770 116.57254.1502791.528 ^ 0.00311.70511.605 4.229 0.056 0.6902809.866 185ZLS31.768 116.57155.7672790.467 ^ 0.00312.20411.767 4.410 0.058 0.7162809.258 186ZLS31.710 116.6314.0882790.253 ^0.004 3.74416.4461.3530.018 0.7362803.585 187ZLS31.712 116.62011.0062788.535 ^0.005 1.60916.3240.5810.008 0.7592803.074 188ZLS31.713 116.60912.3292789.231 ^0.006 1.20116.1930.4340.006 0.6922803.965 189ZLS31.712 116.61510.4992789.758 ^0.007 1.76516.2510.6380.008 0.7532804.131 190ZLS31.714 116.60414.6982790.346 ^0.009 0.47016.1270.1700.002 0.6952805.471 191ZLS31.715 116.59817.0182791.367 ^0.0090.24616.057 0.089 0.001 0.6942806.877 192ZLS31.716 116.59218.9832792.158 ^0.0100.85315.987 0.308 0.004 0.6872807.989 193ZLS31.716 116.58623.0542792.131 ^0.0112.10915.919 0.762 0.01 0 0.6902808.686 194ZLS31.717 116.58123.4842793.498 ^0.0122.24215.857 0.810 0.011 0.6972810.068 195ZLS31.718 116.57624.7022794.359 ^0.0122.61715.793 0.946 0.012 0.7002811.098 196ZLS31.719 116.57036.3292792.842 ^0.0146.20615.717 2.242 0.029 0.6942811.785 197ZLS31.761 116.6174.2002792.747 ^0.018 3.70912.3001.3400.018 0.6992801.979 198ZLS31.759 116.6134.1812793.172 ^0.020 3.71512.4741.3420.018 0.7472802.524 199ZLS31.760 116.6074.7742794.388 ^0.021 3.53212.4021.2760.017 0.7402803.790 200ZLS31.761 116.6025.9422795.424 ^0.022 3.17212.3241.1460.015 0.7272804.989 201ZLS31.762 116.5967.6102796.118 ^0.022 2.65712.2510.9600.013 0.7262805.936 202ZLS31.763 116.5909.4992797.079 ^0.024 2.07412.1980.7490.010 0.7442807.194 203ZLS31.763 116.58514.2362797.531 ^0.025 0.61212.1340.2210.003 0.7492808.503 204ZLS31.764 116.57816.2932798.659 ^0.0260.02312.051 0.0080.000 0.7302809.968 205ZLS31.765 116.57318.8842798.317 ^0.0280.82211.988 0.297 0.004 0.7342810.064 206ZLS31.766 116.56821.5462797.928 ^0.0281.64411.923 0.594 0.00 8 0.7372810.127 207ZLS31.761 116.56824.0472796.012 ^0.0302.41512.284 0.873 0.011 0.6842809.112 208ZLS31.734 116.6195.4042790.935 ^0.043 3.33814.4981.2060.016 0.7492802.524 209ZLS31.737 116.6136.1572791.992 ^0.045 3.10514.2381.1220.015 0.6832803.533 210ZLS31.742 116.6146.1292791.690 ^0.047 3.11413.8851.1250.015 0.7432802.812 211ZLS31.746 116.6136.1032791.885 ^0.048 3.12213.5041.1280.015 0.6942802.668 212ZLS31.751 116.6145.6722792.032 ^0.049 3.25513.1631.1760.015 0.6892802.394 213ZLS31.755 116.6135.8712792.632 ^0.051 3.19412.8181.1540.015 0.7562802.619 214ZLS31.612 116.66541.0272805.912 ^ 0.0107.65624.410 2.766 0.036 0.7562834.430 215ZLS31.616 116.66538.7172806.223 ^ 0.0126.94324.023 2.509 0.033 0.6972833.962 216ZLS31.620 116.66432.4392807.297 ^ 0.0135.00523.762 1.809 0.024 0.7022833.543 217ZLS31.624 116.66235.5022805.592 ^ 0.0145.95023.449 2.150 0.028 0.7302832.098 218ZLS31.628 116.65942.3462802.956 ^ 0.0158.06323.096 2.913 0.038 0.7122830.466 219ZLS31.634 116.65739.9902802.889 ^ 0.0167.33622.639 2.651 0.035 0.7282829.466 220ZLS31.638 116.65437.4552802.751 ^ 0.0176.55322.289 2.368 0.031 0.6942828.517 221ZLS31.644 116.65315.1102806.428 ^ 0.018 0.34221.8300.1240.002 0.6972827.361 222ZLS31.648 116.65120.1032804.581 ^ 0.0211.19821.464 0.433 0.006 0.6742826.151 223ZLS31.653 116.65022.7262801.865 ^ 0.0252.00821.102 0.725 0.010 0.7172823.548 224ZLS31.659 116.64918.0822798.916 ^ 0.0260.57520.567 0.208 0.003 0.7352819.138 225ZLS31.665 116.64797.8692784.420 ^ 0.03125.19720.131 9.104 0.120 0.7092819.846 226ZLS31.669 116.650111.1932782.950 ^ 0.03529.30919.761 10.590 0.139 0.7622820.563 227ZLS31.673 116.653103.1482785.285 ^ 0.03626.82619.443 9.693 0.127 0.7062821.063 228ZLS31.677 116.653209.9182762.752 ^ 0.03759.77519.112 21.599 0.284 0.7202819.074 229ZLS31.680 116.648300.1742745.772 ^ 0.03987.62818.856 31.663 0.416 0.7432819.473 230ZLS31.684 116.645370.3522731.250 ^ 0.040109.28518.562 39.488 0.518 0.7212818.410 231ZLS31.688 116.650381.1822729.685 ^ 0.042112.62718.197 40.696 0.534 0.7632818.558 250ZLS31.708 116.67779.7622799.4662795.816 0.0200.00019.60916.645 7.085 0.093 0.7322824.140 251ZLS31.704 116.674109.3292793.5982789.948 0.0350.00028.73316.973 10.382 0.136 0.7222824.379 252ZLS31.699 116.673123.4852789.8722786.222 0.0450.00033.10217.323 11.961 0.157 0.7372823.747 253ZLS31.698 116.668153.9302783.0072779.357 0.0550.00042.49717.431 15.356 0.202 0.7122822.961 254ZLS31.698 116.664232.9982766.6702763.020 0.0650.00066.89817.414 24.172 0.317 0.7082822.070 255ZLS31.694 116.660263.8512760.5302756.880 0.0700.00076.41917.794 27.613 0.362 0.7552822.293 256ZLS31.693 116.655323.1842747.1172743.467 0.0700.00094.72917.849 34.229 0.449 0.7442820.554 257ZLS31.691 116.645439.2712717.7852714.135 0.0800.000130.55318.021 47.173 0.619 0.7302814.107 258ZLS31.686 116.641449.4392715.5752711.925 0.0810.000133.69118.393 48.307 0.634 0.7672814.221 259ZLS31.713 116.467186.8102759.5992755.9490.1600.01852.64416.201 19.022 0.250 0.7242804.941 260ZLS31.708 116.471177.2672760.7152757.0650.1500.02149.69916.543 17.958 0.236 0.7252804.518 261ZLS31.705 116.475172.6312761.3122757.6620.1500.02348.26816.778 17.441 0.229 0.6852804.481 262ZLS31.703 116.479167.5202762.4782758.8280.1500.02446.69116.977 16.871 0.221 0.6922804.839 263ZLS31.700 116.484163.5592763.4692759.8190.1450.02545.46917.212 16.429 0.216 0.7172805.258 264ZLS31.697 116.489144.1362768.2762764.6260.1400.02739.47517.471 14.264 0.187 0.7142806.521 26 5ZLS31.694 116.494135.4172770.6412766.9910.1300.02936.78417.714 13.291 0.174 0.6732807.451 266ZLS31.691 116.498127.5052772.9602769.3100.1300.03034.34317.974 12.409 0.163 0.7442808.411 267ZLS31.688 116.503113.1692774.3042770.6540.1250.03229.91818.205 10.810 0.142 0.6962807.223 268ZLS31.684 116.508109.8532776.4892772.8390.1150.03328.89518.497 10.441 0.137 0.7222809.013 269ZLS31.682 116.513106.5392779.6602776.0100.1050.03427.87218.691 10.071 0.132 0.7172811.723
65 Appendix A: (Continued) 270ZLS31.678 116.51997.6332781.1522777.5020.1000.03725.12418.988 9.078 0.119 0.7492811.732 271ZLS31.676 116.52193.6252781.6812778.0310.0850.03923.88719.155 8.631 0.113 0.7032811.672 272ZLS31.727 116.57918.1582798.7022795.0520.0050.0060.59815.078 0.216 0.003 0.7312809.778 273ZLS31.726 116.58417.1272797.7802794.130 0.0050.0090.28015.127 0.101 0.001 0.7052808.716 274ZLS31.726 116.59015.0002797.4892793.839 0.0150.010 0.37715.1810.1360.002 0.6932808.063 275ZLS31.725 116.59610.8322797.2512793.601 0.0250.013 1.66315.2620.6010.008 0.7062807.065 276ZLS31.724 116.60212.1622796.4712792.821 0.0400.017 1.25215.3480.4530.006 0.7252806.593 277ZLS31.723 116.6108.3322795.2752791.625 0.0450.019 2.43415.4320.8800.012 0.7402804.710 278ZLS31.750 116.6154.7872795.2812791.6310.0350.003 3.52813.2561.2750.017 0.7122801.971 279ZLS31.750 116.6107.6562796.0952792.4450.0410.004 2.64313.1910.9550.013 0.7152803.282 280ZLS31.751 116.6047.1652796.9382793.2880.0480.005 2.79413.1211.0100.013 0.7192803.962 281ZLS31.752 116.5988.3682794.5602790.9100.0550.005 2.42313.0480.8760.011 0.7152801.757 28 2ZLS31.753 116.59310.9012798.2152794.5650.0620.006 1.64212.9720.5930.008 0.7022805.851 283ZLS31.755 116.57916.7022799.9232796.2730.0750.0060.14912.802 0.054 0.001 0.7372808.501 284ZLS31.756 116.57219.9762799.7542796.1040.0920.0081.15912.724 0.419 0.005 0.7252808.922 285ZLS31.757 116.56524.8822799.0932795.4430.1000.0082.67312.627 0.966 0.013 0.6912809.166 286ZLS31.758 116.55630.7342798.6262794.9760.1050.0094.47912.527 1.618 0.021 0.7172809.722 287ZLS31.759 116.54835.4472797.9272794.2770.1100.0105.93312.447 2.144 0.028 0.7122809.874 288ZLS31.760 116.54041.5372797.0542793.4040.1180.0107.81312.354 2.823 0.037 0.6872810.132 289ZLS31.763 116.53542.7802795.9842792.3340.1300.0118.19612.155 2.962 0.039 0.6842809.120 290ZLS31.769 116.53148.0722794.1192790.4690.1400.0139.83011.631 3.552 0.047 0.6952807.764 291ZLS31.770 116.52555.6502792.2762788.6260.1500.01412.16811.576 4.397 0.058 0.7112807.341 292ZLS31.771 116.51957.7522790.0522786.4020.1550.01512.81711.481 4.631 0.061 0.6762805.472 293ZLS31.772 116.51563.1422787.8402784.1900.1600.01514.48011.395 5.232 0.069 0.6552804.254 294ZLS31.769 116.51069.1692787.0472783.3970.1600.01816.34011.655 5.904 0.078 0.6472804.906 295ZLS31.764 116.50888.3142785.3442781.6940.1600.01922.24812.023 8.039 0.106 0.6802807.281 296ZLS31.759 116.510107.9742783.2682779.6180.1630.02128.31512.427 10.231 0.134 0.6982809.440 297ZLS31.756 116.506148.3032776.7802773.1300.1500.02240.76112.721 14.728 0.193 0.7402811.079 298ZLS31.701 116.6297.8912798.8692795.2190.0700.030 2.57017.1630.9290.012 0.7132810.080 299ZLS31.703 116.61817.4892790.9362787.2860.0550.0310.39217.032 0.142 0.002 0.7172803.874 300ZLS31.704 116.61221.5952790.4162786.7660.0480.0311.65916.975 0.599 0.008 0.7352804.074 301ZLS31.704 116.60723.8112790.3662786.7160.0400.0322.34216.919 0.846 0.011 0.7482804.380 302ZLS31.705 116.60225.8252790.4062786.7560.0350.0322.96416.851 1.071 0.014 0.7502804.739 303ZLS31.706 116.59520.0802794.1072790.4570.0200.0331.19116.777 0.430 0.006 0.7402807.236 304ZLS31.707 116.58921.1912795.5362791.8860.0100.0341.53416.701 0.554 0.007 0.7352808.801 305ZLS31.707 116.58425.5072796.5892792.9390.0050.0342.86616.648 1.036 0.014 0.7572810.618 306ZLS31.708 116.57825.4712798.1122794.4620.0000.0352.85516.571 1.032 0.014 0.7432812.065 307ZLS31.709 116.57326.0202798.8802795.230 0.0050.0363.02416.505 1.093 0.014 0.7442812.867 308ZLS31.710 116.57041.4962796.1112792.461 0.0100.0367.80016.454 2.818 0.037 0.6952813.119 309ZLS31.709 116.56966.8812791.7222788.072 0.0250.03715.63416.529 5.649 0.074 0.7062813.744 310ZLS31.682 116.601124.7022771.2182767.5680.0300.00233.47718.737 12.097 0.159 0.7582806.797 311ZLS31.686 116.60278.3102780.1322776.4820.0400.00319.16118.382 6.923 0.091 0.7312806.318 312ZLS31.687 116.59660.6562781.9742778.3240.0600.00413.71318.296 4.955 0.065 0.7092804.661 313ZLS31.688 116.58764.7082785.1962781.5460.0800.00514.96318.188 5.407 0.071 0.7472808.548 314ZLS31.689 116.58164.7142787.1702783.5200.0900.00614.96518.123 5.407 0.071 0.7502810.465 315ZLS31.690 116.57963.2642790.0532786.4030.1050.00614.51818.098 5.246 0.069 0.7232813.080 316ZLS31.691 116.56956.8702797.2182793.5680.1180.04012.54417.975 4.533 0.060 0.7352818.838 317ZLS31.652 116.523198.0172758.4832754.8330.1500.00056.10321.138 20.272 0.266 0.7502810.937 318ZLS31.659 116.518155.1472770.1232766.4730.150 0.00142.87320.573 15.491 0.203 0.7052813.671 319ZLS31.666 116.519134.4612773.0852769.4350.145 0.00136.48919.973 13.185 0.173 0.7182811.967 320ZLS31.673 116.520118.3632775.5442771.8940.140 0.00131.52119.448 11.390 0.150 0.7322810.733 321ZLS31.680 116.52792.6792781.3012777.6510.135 0.00123.59518.852 8.526 0.112 0.7342810.863 322ZLS31.684 116.531108.8342779.6142775.9640.130 0.00128.58118.525 10.327 0.136 0.6792812.059 323ZLS31.688 116.535110.0382779.9502776.3000.120 0.00128.95218.232 10.461 0.137 0.7252812.282 324ZLS31.692 116.539108.3492781.4592777.8090.115 0.00128.43117.857 10.273 0.135 0.6862813.120 325ZLS31.695 1 16.543100.3102783.2292779.5790.110 0.00125.95017.647 9.377 0.123 0.7452813.043 326ZLS31.698 116.54984.8092786.8482783.1980.110 0.00121.16717.372 7.648 0.100 0.7432813.356 327ZLS31.705 116.56362.5332792.9262789.2760.100 0.00114.29216.833 5.164 0.068 0.7402814.531 328ZLS31.708 116.56955.4602794.9652791.3150.095 0.00112.10916.624 4.375 0.057 0.7292814.983 329ZLS31.712 116.57046.1792795.4212791.7710.087 0.0019.24516.267 3.341 0.044 0.7072813.280 330ZLS31.716 116.57243.8802795.3952791.7450.080 0.0028.53615.925 3.084 0.040 0.7012812.461 331ZLS31.715 116.564132.4622775.0552771.4050.073 0.00235.87216.025 12.962 0.170 0.7472809.498 332ZLS31.721 116.566141.3712771.3862767.7360.063 0.00238.62215.587 13.955 0.183 0.7092807.163 333ZLS31.724 116.563176.9562768.2692764.6190.048 0.00249.60315.289 17.923 0.235 0.7522810.651 334ZLS31.720 116.57235.8972795.4232791.7730.030 0.002 6.07215.618 2.194 0.029 0.7362810.538 335ZLS31.725 116.57439.4732794.7932791.1430.020 0.0027.17615.193 2.593 0.034 0.7092810.199 336ZLS31.730 116.6224.1652793.9812790.331 0.010 0.002 3.72014.8621.3440.018 0.6992802.128 337ZLS31.731 116.6178.0912794.5812790.931 0.023 0.003 2.50914.7880.9060.012 0.6952803.413 338ZLS31.731 116.6117.7682795.8652792.215 0.030 0.003 2.60814.7130.9420.012 0.6892804.558 339ZLS31.733 116.60312.2702796.4752792.825 0.030 0.003 1.21914.6090.4400.006 0.7232805.911
66 Appendix A: (Continued) 340ZLS31.734 116.5934.5272797.3842793.734 0.037 0.003 3.60814.4801.3040.017 0.7312805.161 341ZLS31.735 116.58613.7592798.0972794.447 0.040 0.003 0.76014.3990.2740.004 0.7152807.613 342ZLS31.681 116.638560.8062687.8462684.196 0.0100.002168.05918.770 60.725 0.797 0.7462808.745 343ZLS31.675 116.636631.6692673.8882670.238 0.0050.002189.92719.296 68.627 0.901 0.7412809.185 344ZLS31.673 116.629615.7182676.3772672.7270.0100.002185.00519.434 66.848 0.878 0.7442808.704 345ZLS31.673 116.624643.1512668.1422664.4920.0100.002193.47119.462 69.907 0.918 0.7752805.833 346ZLS31.668 116.621593.2742684.2102680.5600.0260.003178.07919.844 64.346 0.845 0.7482812.567 347ZLS31.665 116.613653.0242670.2782666.6280.0400.003196.51820.102 71.008 0.932 0.7432810.601 348ZLS31.662 116.607758.3642645.6522642.0020.0500.004229.02520.352 82.754 1.086 0.8122806.774 349ZLS31.661 116.600855.6862615.5132611.8630.0640.004259.05920.424 93.607 1.229 0.8332795.738 350ZLS31.658 116.596972.0612593.6892590.0390.0800.004294.97220.653 106.583 1.399 0.7882796.970 351ZLS31.716 116.66014.0702807.2852803.6350.1300.011 0.66315.9770.2400.003 0.7312818.580 352ZLS31.714 116.65417.9282802.8382799.1880.1240.0130.52716.125 0.190 0.002 0.7542815.005 353ZLS31.710 116.64917.9082800.1712796.5210.1200.0140.52116.461 0.188 0.002 0.7562812.662 354ZLS31.707 116.64216.0442797.4952793.8450.1200.016 0.05416.7370.0200.000 0.6862809.966 355ZLS31.703 116.63813.1442797.3352793.6850.1160.017 0.94916.9980.3430.005 0.7562809.425 356ZLS31.698 116.63617.4282798.0172794.3670.1100.0180.37317.409 0.135 0.002 0.6852811.419 357ZLS31.695 116.63114.2682797.1892793.5390.1100.020 0.60317.6710.2180.003 0.7582810.161 358ZLS31.686 116.624106.4832779.2102775.5600.0650.03127.85518.406 10.065 0.132 0.7572810.901 359ZLS31.714 116.543104.9662783.9552780.305 0.0300.00027.38716.110 9.896 0.130 0.6942813.053 360ZLS31.718 116.539244.0242754.7942751.144 0.030 0.00170.30015.804 25.402 0.333 0.7402810.745 361ZLS31.720 116.534305.2952742.4062738.756 0.020 0.00189.20815.617 32.234 0.423 0.7672810.138 362ZLS31.721 116.528198.5842763.7522760.102 0.020 0.00156.27715.559 20.335 0.267 0.7622810.557 363ZLS31.720 116.522173.0632767.8232764.173 0.020 0.00148.40215.577 17.489 0.230 0.7062809.708 364ZLS31.725 116.519185.2932765.4322761.782 0.015 0.00152.17615.193 18.853 0.247 0.7392809.298 365ZLS31.730 116.522195.7562764.8022761.152 0.010 0.00255.40514.829 20.020 0.263 0.7082810.387 366ZLS31.734 116.522204.4422763.9812760.331 0.006 0.00258.08514.482 20.988 0.276 0.6822810.948 367ZLS31.739 116.524213.6112763.4572759.8070.000 0.00260.91514.106 22.010 0.289 0.6972811.833 368ZLS31.742 116.519242.0332758.2502754.6000.005 0.00269.68613.812 25.180 0.331 0.6822811.912 369ZLS31.744 116.513231.4522760.8712757.2210.015 0.00266.42013.672 24.000 0.315 0.6 682812.348 370ZLS31.744 116.506220.4862762.4762758.8260.020 0.00263.03613.662 22.777 0.299 0.7552811.716 371ZLS31.748 116.503194.4022768.3062764.6560.030 0.00254.98713.367 19.869 0.261 0.7242812.190 372ZLS31.753 116.505160.6162774.8172771.1670.030 0.00344.56012.919 16.101 0.211 0.7432811.624
67 Appendix B: Collected Magnetic Data Magnetic data is included on the CD which accompanies this thesis.
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Constraining the geometry and evolution of the maneadero basin, baja california, mexico
h [electronic resource] /
by Sean Callihan.
[Tampa, Fla] :
b University of South Florida,
Title from PDF of title page.
Document formatted into pages; contains X pages.
Thesis (M.S.)--University of South Florida, 2010.
Includes bibliographical references.
Text (Electronic thesis) in PDF format.
Mode of access: World Wide Web.
System requirements: World Wide Web browser and PDF reader.
ABSTRACT: The Maneadero Basin is identified as a transtensional sedimentary basin along the Agua Blanca Fault (ABF) in the southern limit to the "Big Bend" Domain of the North American-Pacific plate boundary zone. The ABF exhibits both the dextral and normal components of slip. This creates an interesting setting for the formation of the Maneadero Basin because structures with orientations similar to the ABF are typically contractional (e.g.: Puente Hills Fault, Whittier Fault, and Rancho Cucamonga Fault). The question if this basin is evidence of plate-scale transtension or local extension associated with bends/stopovers along the ABF is addressed by this study with three working hypotheses. The hypotheses presented by this study are: 1) the basins formed by a dip-slip component on the ABF and truly are an expression of regional transtension, 2) the basins formed at right steps along the dextral ABF, or 3) the basins formed as a result of juxtaposing basement blocks with disparate topographies. Each of these hypotheses would produce unique basin geometries and structures within and around the Maneadero Basin. To test these aforementioned hypotheses, a multi-disciplined study was conducted in the basin. A structural dataset was collected to identify kinematics and offsets of faults both within and bounding the basin. A gravity survey was also conducted to image the basin geometry. The results of the study show an asymmetrical gravity anomaly that closely follows the trace of the ABF. The amplitude of the anomaly is 54 mGal, the gradient of which is steepest around the ABF and shallows away from the fault to the north and east. Forward models of this anomaly indicate the ABF is a steeply north dipping fault. The gravity anomaly also indicates that the deepest part of the basin is located close to, but not coincident with the ABF and the basin gradually shallows to the northeast. This geometry is consistent with the hypothesis that the basin results from dip-slip on the ABF. This idea is also supported by the structural data, which includes fluvial terraces that have been uplifted and offset by faulting on the ABF, and by the presence of a normal fault on the ABF in the center of the basin. The third hypothesis is also supported by models of the gravity data, which suggest a deep (~900m) bowl shaped erosional feature in the bedrock. Dextral slip on the ABF juxtaposes the topographically high Punta Banda Ridge with this topographically low feature. Overall, the data presented in this study suggest the formation of the Maneadero Basin results from is a combination of the dip-slip component on the ABF and juxtaposition of the topographically elevated Punta Banda Ridge with a topographically lower basin of Bahia Todo Santos and Valle Maneadero. Geodetic data strongly suggest that the difference in motion of the Baja Microplate (south of the ABF) to the disrupted southern California Block (north of the ABF), and the orientation of the ABF relative to that motion, is causing transtension in the Maneadero Basin. This combined with strike-slip juxtaposition of different topographies allowed for the formation and evolution of the Maneadero Basin.
Advisor: Paul Wetmore, Ph.D
Agua Blanca fault
t USF Electronic Theses and Dissertations.