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Geological Sciences Theses and Dissertations Abstracts: 2013

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The 2013 abstracts are from Undergraduate Senior Honors Theses, Master's Theses, and PhD Dissertations completed at the University of Texas at Austin in the field of Geological Sciences. See the Geological Sciences Theses and Dissertations Index : 2013 for a more concise listing of authors, titles, and supervisors. Dissertation abstracts published prior to 2001 may be found through Dissertations and Theses: Full Text.


Mohammed Abdullah Alhussain, Ph.D

University of Texas at Austin, May 2013

Supervisor: Mrinal K. Sen

138 pages, 76 references, 1 table

Estimation of reservoir fracture parameters, fracture orientation and density, from seismic data is often difficult because of one important question: Is observed anisotropy caused by the reservoir interval or by the effect of the lithologic unit or multiple units above the reservoir? Often hydrocarbon reservoirs represent a small portion of the seismic section, and reservoir anisotropic parameter inversion can be easily obscured by the presence of an anisotropic overburden. In this study, I show examples where we can clearly observe imprints of overburden anisotropic layers on the seismic response of the target zone. Then I present a simple method to remove the effect of anisotropic overburden to recover reservoir fracture parameters. It involves analyzing amplitude variation with offset and azimuth (AVOA) for the top of reservoir reflector and for a reflector below the reservoir. Seismic CMP gathers are transformed to delay-time vs. slowness (tau-p) domain. We then calculate the ratio of the amplitudes of reflections at the reservoir top and from the reflector beneath the reservoir. The ratios of these amplitudes are then used to isolate the effect of the reservoir interval and remove the transmission effect of the overburden.

The methodology is tested on two sets of models - one containing a fractured reservoir with isotropic overburden and the other containing a fractured reservoir with anisotropic overburden. Conventional analysis in the x-t domain indicates that the anisotropic overburden has completely obscured the anisotropic signature of the reservoir zone. When the new methodology is applied, the overburden effect is significantly reduced. The methodology is also applied to an actual PP surface reflection (Rpp) 3D dataset over a reservoir in the Arabian Peninsula. Ellipse-fitting technique was applied to invert for two Fracture parameters: (1) Fracture density and (2) fracture direction. Fracture density inversion results indicate increased fracturing in the anticline structure hinge zone. Fracture orientation inversion results agree with Formation MicroImaging (FMI) borehole logs showing a WNW-ESE trend.

This newly developed amplitude ratio method is suitable for quantitative estimation of fracture parameters including normal and tangential “weaknesses” (ΔN and ΔT respectively). Initially, inversion of conventional AVOA for ΔN and ΔT parameters indicates that the ΔN parameter is reliably estimated given an accurate background isotropic parameter estimation derived from borehole logging data. While ΔN parameter inversion is successful, inversion for ΔT parameter from Rpp information is not, presumably due to the dependence of ΔT estimation on many medium parameters for accurate prediction. The ΔN parameter is then successfully recovered when applied to the amplitude ratio values derived from synthetic data. It is important to recognize that ΔN parameter is directly proportional to fracture density and high ΔN values can be attributed to high crack density values.

The ΔN parameter inversion is also applied to the amplitude ratios derived from real seismic data. This inversion requires fracture azimuth data input that is obtained from the fracture direction inversion using ellipse-fitting technique. The background Vp/Vs ratio, estimated from well logs, is another required parameter for ΔN estimation. Inversion results are promising when fracture density computed from ΔN parameter is compared to the facture density computed from ellipse-fitting technique. The maps of both attributes show similarities with more fractures located at the anticline structure hinge. Spatial variability in fracture parameters has proven valuable in locating “sweet spots” areas or highly fractured zones within the reservoir interval.

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Lubna Barghouty, Bachelor of Science

University of Texas at Austin, December 2013

Supervisor: Sergey Fomel

83 pages, 33 references, 2 tables

Free-surface multiples in marine seismic surveys constitute a significant type of noise in the data and a challenge in the seismic processing flow. Previous processing performed on a 2D line of the Viking Graben dataset from the North Sea showed the ineffectiveness of one demutiple method using moveout discrimination to attenuate surface-related multiples. Conventional seismic processing usually employs the labor-intensive step of velocity analysis in multiple attenuation methods exploiting moveout differences and in seismic imaging. In this project, I attempt to perform multiple attenuation and seismic imaging of the 2D data without the need for velocity analysis. We address the problem of surface multiples using the technique of Surface-Related Multiple Elimination (SRME), which generates a model of the multiples by autocon-volution of the seismic data and then adaptively subtracts the multiples. Multiple prediction and subtraction requires neither primary velocity estimation by velocity analysis nor wavelet estimation. The results of SRME proved satisfactory in adapting the predicted multiples to the actual multiples necessary for multiple elimination.

Since multiples were predicted from the data itself, preprocessing of the data such as missing trace interpolation was crucial for accurate multiple prediction. Imaging the data using a non-conventional method of Velocity-Independent Time-Domain Imaging was a suitable imaging step following SRME because it relies on dip estimation rather than velocity analysis to perform imaging tasks such as migration to zero offset and prestack time migration. A time-domain image was constructed of the 2D line showing diffraction patterns not collapsed by migration. Improvements on the migration results can be made by improving the dip estimation necessary for the imaging step, assuming the diffraction sources are not outside the 2D line.

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Jesse Berney, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Jack Holt

49 pages, 18 references

Debris-covered glaciers on Mars offer evidence that global climate change on Mars is governed by orbital forcings, in particular cyclical changes in obliquity. These glaciers or Lobate Debris Aprons (LDA) represent the movement of water from the poles to lower latitudes and can help constrain the quantities of water being transported during earlier parts of Mars's history. LDA also comprise a primary accessible quantity of water for future missions. By studying the characteristics of LDA in a regional sense, we can gain insight into modes of formation for these "Lobate Debris Aprons" and how they continue to exist in today's hostile climate. When examined with radar, LDA in the Deuteronilus Mensae and Tempe Mareotis regions of the northern hemisphere show a variation in reflective properties which correlates with geologic age of nearby escarpments, suggesting that the variation in radar properties may represent a difference in the properties of the debris cover rather than in the glaciers beneath.

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Robert Wayne Burroughs, M.S.Geo.Sci.

University of Texas at Austin, August 2013

Supervisor: Christopher J. Bell

301 pages, 117 references

There are more than 300 species of extant turtles, the majority of which belong to the Testudinoidea. Here I describe a new box turtle from the Eocene-Oligocene boundary of west Texas. This specimen impacts the phylogeny of Testudinoid turtles by pulling the divergence of extant Testudinoid turtles back in time approximately 25 million years. This results in a need to refocus on paleontological research of Testudinoid turtles into the late Paleogene and early Neogene to identify fossil localities and specimens that can help further elucidate the evolution of the group. New work on the fossil record of turtles also requires a re-evaluation of methods used for identifying and evaluating the evolutionary history of turtles as a group. An implicit assumption over the last 150 years of turtle paleontology was that both turtle shells and turtle heads reveal congruent and complimentary evolutionary relationships. This assumption was never adequately tested. I utilized a series of methods to evaluate the congruency of phylogenetic hypotheses using disparate anatomical regions. Using a dataset of extant Emydid turtles, I evaluated whether turtle shells and turtle heads provided congruent and complimentary phylogenetic hypotheses. My methods employed parsimony-based reconstruction, maximum-likelihood-based reconstruction, and Bayesian-based reconstruction, including Bayesian-partition analyses. My conclusions are that heads and shells do not provide fully congruent topologies, and that in many cases there is a loss of phylogenetic resolution when only turtle sklls are used to generate phylogenies. The implication is that a focus on a robust and complete dataset of anatomical features will provide the best basis for further investigation of fossils. My work also provides a framework for dataset exploration by providing a method to identify the most robust phylogenetic signal found within a dataset. This framework will allow non-turtle paleontologists and systematists the ability to further investigate their own datasets and develop robust hypotheses of evolutionary relationships across the diversity of the tree of Life.

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Joshua Bruce Burrus, M.S.Geo.Sci.

University of Texas at Austin, May 2013

Supervisor: Daniel Stockli

104 pages, 90 references, 5 tables

The Weepah Hills Area (Nevada) exposes exhumed metamorphic and plutonic rocks and upper-plate (supradetachment) volcano-sedimentary rocks that have experienced a complex, multi-stage deformational and depositional history. The Weepah Hills metamorphic core complex (WHMCC) is located in a region of the western Cordillera that was affected by both Miocene Basin-and-Range style E-W extension and Mio-Pliocene Walker Lane transcurrent shearing. Mio-Pliocene transcurrent deformation is transferred across a ~175 km releasing bend, known as the Mina Deflection, that kinematically links dextral strike-slip faults of the Death Valley-Fish Lake Valley with the central Walker Lane Belt. Progressive Mio-Pliocene transtension is characterized by core complex detachment faulting and younger high-angle normal faults. Timing of detachment faulting is constrained by both (U-Th)/He thermochronometry of footwall rocks and detailed chronostratigraphy of upper-plate strata to between 9-6 Ma. This age is supported by deformation recorded in the upper-plate strata that is attributed to progressive folding of the detachment associated with corrugation development. Earlier Miocene Basin-and-Range style extension is characterized by N-S trending high-angle normal faults and half-grabens that are strongly overprinted by Mio-Pliocene structures. (U-Th)/He zircon cooling ages from the detachment footwall range from ~12-20 Ma and are attributed to exhumation and unroofing related to E-W Basin-and-Range extension. New detailed sedimentological and geochronologic data show that, in contrast to previous research, the WHMCC upper-plate strata do not form a single supradetachment package, but rather three temporally distinct Miocene stratigraphic packages bounded by angular unconformities. The stratigraphic, structural, and exhumational record preserved in the WHMCC elucidates the timing of deformation and sedimentary basin evolution related to both Basin-and-Range E-W extension and Walker Lane related NW-directed transtension.

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Jason Neal Camacho, ASc.

University of Texas at Austin, December 2013

Supervisor: Charles Kerans

47 pages, 37 references, 3 tables

The Guadalupe Mountains are a widely recognized field laboratory for carbonate geology. They are also analogous to the prolific West Texas Field. Preferential regional-scale trellis style weathering patterns driven by Syndepositional deformation exist throughout the southeastern front of the Guadalupe Mountains. This study examines the relationship between the anomalous outcrop scale high-relief elongate fin structures in the mouth of Slaughter Canyon and preferential erosion related to the differential incidence of Syndepositional fractures. This relationship was investigated by integrating traditional field controlled fracture mapping with a remote survey done via digital outcrop model to quantify the frequency and incidence of the fracture network at the mouth of Slaughter Canyon, NM.

After field and remote surveys were conducted, built-for-purpose fracture diagnostic software using a normalized correlation count was implemented in the analysis. Results show that there is an inverse relationship between high density zones of deformation and the fin structures and an average syndepositional fracture density of ~28 m in the gullies and ~14 m in the fins. This ratio is smaller than that observed elsewhere in the Guadalupe Mountains. This smaller ratio could be the driver behind the high relief erosional fins that are prevalent on the south western wall of Slaughter Canyon.

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Brandee Carlson, Bachelor of Science

University of Texas at Austin, December 2013

Supervisor: Wonsuck Kim

26 pages, 12 references, 1 table

Autogenic processes are inherent processes in sediment transport that influence landscape building and leave distinct signatures in the sedimentary record. It is of great interest to understand autogenic processes better in order to clearly decouple the stratigraphic products generated by external controls (e.g., tectonics or climate change) from internal dynamics. Here we present results from a series of delta-building experiments designed to determine the response of the fluviodeltaic autogenic timescales and processes to varying basin water depth. These internal dynamics have a characteristic timescale that is required for the delta topset to be reworked through a full cycle of storage and release of sediment. The topset aggrades by fluvial sedimentation until it reaches a maximum slope, at which point a large amount of sediment is released, typically via a strong channelization. This is followed by a period of channel migration, avulsion, and backfilling, and the cycle is repeated. We used time-lapse images to track shoreline positions and observe changes in progradation rate. The experimental results indicate that the autogenic timescale generally increases with increasing basin water depth. These observations may be explained by the amount of time required to build a lobe with an area large enough to trigger a switch from a lobe-building release event to a backfilling storage event. Each deposit was allowed to prograde to the same length of 1m to ensure that topset area was consistent and that basin depth was an isolated variable between experiments. Individual lobes show a similar average surface area regardless of basin depth in the experiments. Deeper basin depth simply requires a larger volume to be filled within this area, thus more time to complete one autogenic process. However, when channel depth is significantly smaller than basin depth, e.g., in very deep basins, stochastic variability in sediment transport and channel lateral mobility outweighs the autogenic cyclicity. Basin depth also seems to control the width and elongation of individual lobes due to channel geometry and lateral migration. Shallower basin depths are more conducive to lateral migration during lobe building, resulting in wider lobes. Deeper basin depth allows less lateral migration, resulting in more elongate lobe building. This study suggests that internal dynamics controls the shape and size of the lobe stratigraphic building unit in fluviodeltaic systems and can be useful to interpret relative basin depth at the time of deposition.

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Katherine Lynn Delbecq MSGeoSci

University of Texas at Austin, May 2013

Supervisors: Wonsuck Kim and David Mohrig

37 pages, 44 references, 2 tables

A key goal of tsunami research is to quantitatively reconstruct flow parameters from paleotsunami deposits in order to better understand the geohazards of coastal areas. These reconstructions rely on grain-size and thickness measurements of tsunami deposits, combined with simple models that allow an inversion from deposit characteristics to wave characteristics. I conducted flume experiments to produce a data set that can be used to evaluate inversion models for tsunami deposition under controlled boundary conditions. Key variables in the flume experiments are sediment grain-size distribution, flow velocity and depth, and depth of water ponded in the flume before the tsunami bore was released. Physical experiments were run in a 32 m-long outdoor flume at The University of Texas at Austin. The flume has a head box with a specialized mechanical lift gate that allows instantaneous release of water to create a bore. Various sediment mixtures (silt to very coarse sand) are introduced to the upstream end of the channel as a low dune positioned just below the lift gate. The bore entrained the sediment mixture, producing an unambiguous suspension-dominated deposit in the downstream half of the channel. Deposits were sampled for grain-size and thickness trends. The experimental results capture characteristics of many recent and paleotsunami deposits, including consistent fining in the transport direction. In addition to overall fining, trends in deposit sorting and coarse (D95) and fine (D10) fractions reveal the importance of sediment-source grain-size distribution on tsunami deposit attributes.

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John Boone DeSanto, B.S.

University of Texas at Austin, May 2013

Supervisor: Donald Blankenship

34 Pages, 21 references, 1 table

The Amundsen Sea Embayment of the West Antarctic ice sheet (WAIS) is currently one of the most rapidly changing sectors of a continental ice sheet. As a marine ice sheet, the WAIS is in a potentially unstable configuration. A model is proposed to evaluate the effect of geothermal flux on flow in ice streams using ice layer drawdown anomalies, features identifiable by a thick layer package resting on top of deformed ice. Drawdown anomalies represent either significant loss or mechanical deformation of basal ice.

Several features with the geometry of drawdown anomalies are identi¬fied in Thwaites Glacier along an ice stream tributary near Mt. Takahe. These anomalies correlate with the surface ice velocity and have thick layer packages age at a constant rate, implying deformation at a single origin corresponding to an upstream edifice. The abnormal amplitude of upstream drawdown anomalies implies a thermal event at the same edifice 1000-2000 years ago. This provides another example of high heterogeneous geothermal flux in the WAIS.

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Joshua Francis Dixon, PhD

University of Texas at Austin, May 2013

Supervisor: Ronald J. Steel

217 pages, 139 references, 4 tables

This research investigates the character and significance of shelf-edge deltas within the sedimentary source-to-sink system, and how variability at the shelf edge leads to different styles of deep-water deposition. Because the shelf-edge represents one of the key entry points for terrigenous sediment to be delivered into the deep water, understanding of the sedimentary processes in operation at these locations, and the character of sediment transported through these deltas is critical to understanding of deep-water sedimentary systems. The research was carried out using three datasets: an outcrop dataset of 6000 m of measured sections from the Permian-Triassic Karoo Basin, South Africa, a 3D seismic data volume from the Eocene Northern Santos Basin, offshore Brazil and a dataset of 29 previously published descriptions of shelf-edge deltas from a variety of locations and data types.

The data presented highlight the importance of sediment instability in the progradation of basin margins, and deep-water transport of sediment. The strata of the Karoo Basin shelf margin represent river-dominated delta deposits that become more deformed as the shelf-edge position is approached. At the shelf edge, basinward dipping, offlapping packages of soft-sediment-deformed and undeformed strata record repetitive collapse and re-establishment of shelf-edge mouth bar packages. The offlapping strata of the Karoo outcrops record progradation of the shelf margin through accretion of the shelf-edge delta, for over 1 km before subsequent transgression. The Eocene Northern Santos Basin shelf margin, in contrast, exhibits instability features which remove kilometers-wide wedges of the outer shelf that are transported to the basin floor to be deposited as mass-transport packages. In this example, shelf-edge progradation is achieved through ‘stable’ accretion of mixed turbidites and contourites.

The data also emphasize the importance of the role of shelf-edge delta processes in the delivery of sediment to the basin floor. A global dataset of 29 examples of shelf-edge systems strongly indicates that river domination of the shelf-edge system (as read from cores, well logs or isopach maps) serves as a more reliable predictor of deep-water sediment delivery and deposition than relative sea level fall as traditionally read in shelf-edge trajectories or sequence boundaries.

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Mark Hamilton Duncan, MS Geosciences

University of Texas at Austin, May 2013

Supervisors: Gail Christeson, Harm Van Avendonk

80 pages, 47 references, 1 table

The Gulf of Mexico Basin Opening project (GUMBO) is a study of the lithological composition and structural evolution of the Gulf of Mexico (GoM) that uses Ocean Bottom Seismometer (OBS) data from four transects in the Northern GoM. I examine 39 OBS shot records in the easternmost transect for shear wave arrivals and pick shear wave travel times from the 11 usable records. I then carry out a tomographic inversion of seismic refraction travel times. I use the resulting shear-wave velocity model in conjunction with a previously constructed P-wave model to examine the relationship between Vp and Vs. I compare velocities in the sediment and basement with empirical velocities from previous studies for the purpose of constraining lithological composition below the transect and make an interpretation of the structural evolution of the eastern GoM.

The seismic velocities for crust landward of the Florida Escarpment are consistent with normal continental crust. Seaward of the Escarpment, velocities in the upper oceanic crust are anomalously high (Vp = 6.5 – 7 km/sec; Vs = 4.0 – 4.6 km/sec). A possible explanation for this observation is that GoM basalt formation consisted of basaltic sheet flows, forming oceanic crust that does not contain the vesicularity and lower seismic velocities found in typical pillow basalts. Increased magnesium and iron content could also account for these high velocities.

Seismic refraction and reflection data provide a means of investigating the nature of the Moho in the northeastern GoM. I use a finite difference method to generate synthetic record sections for data from eight instruments that are part of the two easternmost GUMBO seismic lines (lines 3 & 4). I then vary the thickness of the Moho in these synthetic models and compare the results with the original receiver gather to examine the effects this variability has on amplitudes.

The data from the instruments chosen for these two lines are representative of continental and transitional crust. The finite difference models indicate that the Moho beneath GUMBO 3 is ~1500 m thick based on the onset and amplitudes of PmP arrivals. All five instruments display consistent results. The instruments along GUMBO 4 suggest a Moho almost twice as thick as GUMBO 3 on the landward end of the transect that grades into a Moho of similar thickness (1750 m) in the deep water GoM. The three instruments used to model the Moho in this area show that the Moho ranges from ~1750 to 3500 m in thickness. The sharper boundary beneath continental crust in GUMBO Line 3 supports other evidence that suggests magmatic underplating and volcanism in the northern GoM during the mid-Jurassic. The thicker Moho seen on the landward end of GUMBO Line 4 that is overlain by continental crust was likely unaffected by GoM rifting. Therefore, the Moho beneath the Florida Platform might be as old as the Suwannee Terrane, and complex Moho structure is not uncommon for ancient continental crust.

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Rania Eldam, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Jaime D. Barnes

61 pages, 98 references, 5 tables

Franciscan Complex serpentinites have been interpreted as eroded pieces of the overriding Coast Range Ophiolite (CRO), off-scraped pieces of the subducting oceanic plate off of the present California coast, and as sedimentary serpentinites (e.g., Wakabayashi, 2004); however, most of these interpretations are based on field relationships and tectonic models. This study presents bulk rock major and trace element geochemistry, pyroxene and spinel geochemistry, and stable isotope data (O, H, Cl) for serpentinite samples with the goal of determining protolith origin and subsequent serpentinizing fluid sources of several metasomatized Franciscan and CRO ultramafic rocks in order to decipher the tectonic setting of serpentinization.

This study focuses on serpentinite bodies found in the Franciscan Complex (west of Cuesta Ridge; south of San Francisco; Tiburon Peninsula; Healdsburg) (n = 12). Three samples from Cuesta Ridge (CRO) were also analyzed for comparison. All samples are >~95% serpentinized and consist of lizardite +/- chrysotile. Relict pyroxene grains are rarely preserved.

Franciscan serpentinite samples (Tiburon Peninsula, west of Cuesta Ridge) show positive-sloped REE patterns. Low LREE concentrations are typical of abyssal peridotites. Relict clinopyroxenes from Tiburon Peninsula have high HREE concentrations, also supporting an abyssal origin. Two of the three samples from the Cuesta Ridge show flat REE patterns; whereas, one is U-shaped. This high LREE concentration is similar to forearc peridotites. Spinels from Cuesta Ridge, Sawyer Camp Trail, and Mill Creek Road have Cr# › 0.60 also implying a forearc setting; whereas Franciscan localities from the Tiburon Peninsula and Highway 1 have lower Cr# (0.21 to 0.51). All samples show remarkable positive Ce and Y anomalies. We speculate that these anomalies may be due to interaction with ferromanganese nodules and crusts (also high in Ce and Y) deposited on the seafloor prior to subduction.

Cuesta Ridge samples have O values between +6.0 to +6.6‰. Franciscan serpentinites (except those south of San Francisco) have δ18O values of +5.4 to +7.9‰. These δ18O values are similar to typical oceanic serpentinites and likely represent low-T seawater hydration on the seafloor. δD values of all samples are extremely low (-107 to -90‰) and likely result from post-serpentinization, post-emplacement interaction with meteoric water at low temperature. Samples south of San Francisco lie within the San Andreas Fault zone and have high δ18O values (+7.2 to +9.5‰) and low δD values (-107 to -104‰) likely due to low-T interaction with meteoric water at high fluid-rock ratios. Most of the serpentinites (12 of the 15) have δ37C1 values between +0.2 and +0.9‰, typical values for serpentinites formed by interaction with seawater.

Based on bulk rock geochemistry and pyroxene and spinel compositions, serpentinites located within the Franciscan Complex have geochemical characteristics of abyssal peridotites; whereas, those from Cuesta Ridge are more chemically heterogeneous with most having affinity to forearc peridotites. All stable isotope geochemistry indicates seafloor serpentinization by seawater.

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Baiyuan Gao, M.S.Geo.Sci.

University of Texas at Austin, August 2013

Supervisor: Peter B. Flemings

87 pages, 48 references, 15 tables

A systematic study of how mudstone permeability impacts reservoir pore pressure is important to understand the regional fluid field within sedimentary basins and the control of sediment properties on subsurface pressure. I develop a 2D static model to predict reservoir overpressure from information estimated from the bounding mudstones and structural relief. This model shows that close to a dipping reservoir, the mudstone permeability is high in the up-dip location and low in the down-dip location. This characteristic mudstone permeability variation causes the depth where reservoir pressure equals mudstone pressure (equal pressure depth) to be shallower than the mid-point of the reservoir structure. Based on the 2D static model, I constructed a nomogram to determine the equal pressure depth by considering both farfield mudstone vertical effective stress and reservoir structural relief. I find the equal pressure depth becomes shallower with decreasing vertical effective stress, increasing reservoir structural relief, and increasing mudstone compressibility. Pressure predicted by the static model agrees with pressure predicted by a more complete model that simulates the evolution of the basin and is supported by field observations in the Bullwinkle Basin (Green Canyon 65, Gulf of Mexico). This study can be applied to reduce drilling risk, analyze trap integrity, and facilitate safe and efficient exploration.

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Marlo Rose Gawey, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisors: Daniel Breecker, Katherine Romanak, Toti Larson

104 pages, 123 references, 10 tables

Perfluorocarbon tracers (PFTs) are commonly proposed tracers for use in carbon capture and sequestration (CCS) leak detection and vadose zone monitoring programs. Tracers are co-injected with supercritical CO2 and monitored in the vadose zone to identify leakage and calculate leakage rates. These calculations assume PFTs exhibit “ideal” tracer behavior (i.e. do not sorb onto or react with porous media, partition into liquid phases or undergo decay). This assumption has been brought into question by lab and field evaluations showing PFT partitioning into soil contaminants and sorbing onto clay. The objective of this study is to identify substrates in which PFTs behave conservatively and quantify non-conservative behavior. PFT breakthrough curves are compared to those of a second, conservative tracer, sulfur hexafluoride (SF6). Breakthrough curves are generated in 1D flow-through columns packed with 5 different substrates: silica beads, quartz sand, illite, organic-rich soil, and organic-poor soil. Constant flow rate of carrier gas, N2, is maintained. A known mass of tracer is injected at the head of the columns and the effluent analyzed at regular intervals for tracers at picogram levels by gas chromatography. PFT is expected to behave conservatively with respect to SF6 in silica beads or quartz sand and non-conservatively in columns with clay or organics. However, results demonstrate PFT retardation with respect to SF6 in all media (retardation factor is 1.1 in silica beads and quartz sand, 2.5 in organic-rich soil, ›20 in organic-poor soil, and ›100 in illite). Retardation is most likely due to sorption onto clays and soil organic matter or condensation to the liquid phase. Sorption onto clays appears to be the most significant factor. Experimental data are consistent with an analytical advection/diffusion model. These results show that PFT retardation in the vadose zone has not been adequately considered for interpretation of PFT data for CCS monitoring. These results are preliminary and do not take into account more realistic vadose zone conditions such as the presence of water, in which PFTs are insoluble. Increased moisture content will likely decrease sorption onto porous media and retardation in the vadose zone may be less than determined in these experiments.

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Gail Ruth Gutowski, M. S. Geo. Sci.

University of Texas at Austin, August 2013

Supervisors: Donald Blankenship and Charles Jackson

48 pages, 27 references, 2 tables

Changes to ice sheet surface mass balance (SMB) are going to play a significant role in future sea level rise (SLR), particularly for the Greenland ice sheet. The Coupled Model Intercomparison Project Phase 5 (CMIP5) found that Greenland ice sheet (GIS) response to changes in SMB is expected to contribute 9 ± 4 cm to sea level by 2100 (Fettweis et al 2013), though other estimates suggest the possibility of an even larger response.

Modern ice sheet geometry and surface velocities are common metrics for determining a model’s predictability of future climate. However, care must be taken to robustly quantify prediction uncertainty because errors in boundary conditions such as SMB can be compensated by (and therefore practically inseparable from) errors in other aspects of the model, complicating calculations of total uncertainty.

We find that SMB calculated using the Community Earth System Model (CESM) differs from established standards due to errors in the CESM SMB boundary condition. During the long ice sheet initialization process, small SMB errors such as these have an opportunity to amplify into larger uncertainties in GIS sensitivity to climate change. These uncertainties manifest themselves in ice sheet surface geometry changes, ice mass loss, and subsequent SLR.

While any bias in SMB is not desirable, it is not yet clear how sensitive SLR projections are to boundary condition forcing errors. We explore several levels of SMB forcing bias in order to analyze their influence on future SLR. We evaluate ensembles of ice sheets forced by 4 different levels of SMB forcing error, covering a range of errors similar to SMB biases between CESM and RACMO SMB.

We find that GIS SMB biases on the order of 1 m/yr result in 7.8 ± 3.4 cm SLR between 1850 and 2100, corresponding to 100% uncertainty at the 2σ level. However, we find unexpected feedbacks between SMB and surface geometry in the northern GIS. We propose that the use of elevation classes may be incorrectly altering the feedback mechanisms in that part of the ice sheet.

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Samuel Franz Hiebert, M.S.GeoSci

University of Texas at Austin, August 2013

Supervisor: Charles Kerans

111 pages, 58 references, 1 table

The San Andres and Grayburg Formations are important stratigraphic units for constructing correlation frameworks of the Guadalupe Mountains because these strata record the transition between the ramp profiles of the San Andres along the Algerita Escarpment and the reef-rimmed platforms of the Capitan Formation of the southern Guadalupe Mountains (Franseen et al. 1989). Sarg et al. (1999) and Kerans and Tinker (1999) have published significantly different models of shelf-to-basin correlations within this stratigraphic interval. Central to the debate is the correlation of mixed carbonate-siliciclastic strata exposed at Plowman Ridge in the Brokeoff Mountains to the better-constrained strata along the Shattuck Escarpment in the Guadalupe Mountains. This study applies high-resolution cyclostratigraphy, inorganic carbon isotope geochemistry, and sequence stratigraphic concepts to test the hypothesis that the strata exposed at Plowman Ridge are equivalent to Grayburg strata exposed at the Shattuck Escarpment in the southern Guadalupe Mountains (Kerans and Nance 1991, Kerans and Kempter 2002).

The shelf-to-basin cyclostratigraphic framework of the Grayburg Formation used in this study was established at the Shattuck Escarpment with data compiled from nine detailed measured sections, high-resolution photopans, and petrographic analysis. Based on one- and two-dimensional cycle stacking analysis, the Grayburg Formation was divided into three high-frequency sequences (HFSs). The high-frequency sequences contain transgressive systems tracts separated by maximum flooding surfaces from the highstand systems tracts. The Grayburg high-frequency sequences are composed of between 6 and 20 high-frequency cycles (HFCs), which were identified and classified into vertical facies successions.

The Grayburg succession at Shattuck section 7 (32.09°, -104.81°) was selected as the reference section from the Guadalupe Mountains for comparison with Plowman section PR1 (32.03°, -104.89°) in the Brokeoff Mountains. Correlation between sections is documented at the 3rd-order composite sequence, high-frequency sequence, and when feasible, high-frequency cycle scale. Three high-frequency sequences recognized at Plowman Ridge section PR1 are equivalent to the G10, G11, and G12 Grayburg sequences described at Shattuck section 7. Correlation of the Grayburg G10-G12 high-frequency sequences with the three sequences at Plowman Ridge is based on comparison of overall thicknesses, facies proportions, cycle number, vertical facies succession, stratigraphic position of diagnostic units, and excursions within the inorganic carbon isotope profiles taken from both sections. Establishing the links between Grayburg strata on the Shattuck wall with strata on Plowman Ridge corroborates the framework/correlation scheme of Kerans and Tinker (1999) in lieu of other published correlation frameworks.

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Mary Catherine Hingst, M.S.Geo.Sci.

University of Texas at Austin, May 2013

Supervisors: Michael Young and Katherine Romanak

112 pages, 82 references, 9 tables

Carbon capture, utilization and storage (CCUS) aims to reduce CO2 emissions by capturing CO2 from sources and injecting it into geologic reservoirs for enhanced hydrocarbon recovery and storage. One concern is that unintentional CO2 and reservoir gas release to the surface may occur through seepage pathways such as fractures and/or improperly plugged wells.

We hypothesize that CO2 and CH4 migration into the vadose zone and subsequent O2 dilution and Eh and pH changes could create an increased potential for metal mobilization, which could potentially contaminate ground and surface waters. This potential has not been addressed elsewhere. Goals of this study are to understand how the potential for metal mobilization through soil pore water may increase due to CO2 and CH4 and to assess potential impact to aquifers and/or the biosphere. The study was conducted at a CCUS site in Cranfield, MS, where localized seepage of CH4 (45%) from depth reaches the surface and oxidizes to CO2 (34%) in the vadose zone near a plugged well. Four sediment cores (4.5-9m long) were collected in a transect extending from a background site through the area of anomalously high soil gas CO2 and CH4 concentrations. Sediment samples were analyzed for Eh and pH using slurries (1:1 vol. with DI water) in the field and for occluded gas concentrations, metal (Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) concentrations, moisture content, organic carbon content, and grain size in the laboratory. Data from the background reference area (no gas anomaly: occluded gas ~21% O2, ‹1% CO2, 0% CH4) showed oxidized conditions (Eh from 464-508mV) and neutral pH (7.0-7.8) whereas samples collected near the gas anomaly (13-21% O2, 0.1-5% CO2, ‹0.1% CH4) were more reducing (Eh 133-566mV) and more acidic (pH = 5.3-8.0). Significant correlations were found between Eh and O2 (r = 0.95), pH and CO2 (r = -0.88), and between these parameters and acid-leachable metals in samples from within the soil gas anomaly. Correlations quickly weaken away from the anomaly. Statistically, total metal concentrations, except for Ba, are similar in all cores. Acid-mobile metal concentrations, above 5m, increase toward the gas anomaly. The percent of water-mobile metals is very low (‹2%) for all metals in all cores, indicating freely-mobile metals are not affected by elevated CO2/CH4. Conclusions are: 1) oxidation of CH4 to CO2 depletes O2 causing reducing conditions; 2) high CO2 and low O2 affect Eh and pH of sediments which in turn alters mineralogy and bond strength between sediments and adsorbed ions; 3) intrusion of strongly acidic fluids (pH of acid used was 0.39) into these sediments could potentially remove weakly bonded metals or dissolve minerals. Implications from this study are that Eh needs to be considered along with pH when analyzing contamination potential, and that exposure of sediments to reducing, followed by acidic conditions, increases the potential for metal mobilization in the vadose zone. More research is needed to determine the concentration of gases (CO2, CH4 and O2) that will create Eh and pH levels that could affect the mineralogy and sorption mechanism potentially leading to metal mobilization. Methods for assessing potential metal mobilization may be useful for site characterization and risk assessment.

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Lei Huang, Ph.D.

University of Texas at Austin, May 2013

Supervisor: Rong Fu

164 pages, 170 references, 8 tables

Convective and long-range transport of air mass controls the global distributions and impacts of the pollutants generated in limited source regions. However, an observational characterization of such transport based on long-term satellite data has been difficult in part because adequate satellite measurements were not available until recent years and lack of an automated method for identifying the transport pathways. My dissertation addresses this problem through three steps: First, I developed a method to automate the identification of two pathways that are responsible for the transport of biomass burning generated tracers from the surface to the upper troposphere (UT). I focused on carbon monoxide (CO) because it has a relatively long lifetime in the atmosphere, and thus it is commonly used as a tracer of convective and long-range mass transport. Next, I applied this method to investigate the relative importance of the two pathways in determining the seasonal pattern of UT CO distribution. Results show that the seasonality of CO concentrations in the tropical UT mainly reflects the seasonality of the “local convection” pathway, because the “local convection” pathway typically transports significantly more CO to the UT than the “advection within the lower troposphere followed by convective transport” pathway. Then, I investigated the impacts of transport pathways on the interannual variation of tropical UT CO concentration. Results show that the interannual variation of CO in the tropical UT is dominated by UT CO anomaly over Southeast Asia related to the El Niño-Southern Oscillation, and the average mass of CO transported per event of “local convection” is the factor that accounts for the UT CO difference between two El Niño periods.

After that, I began to address the transport of more complex pollutants such as aerosols. First, the seasonal and diurnal variations of the vertical distributions of aerosol properties were characterized through a statistical analysis of aerosol profile data. Then, the transport pathways associated with the aerosol layer at the tropopause level over Asian area during boreal summer were investigated through back-trajectory model analyses. Three major pathways were found and the occurrence frequency of each pathway was analyzed and discussed.

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Kyle Kampa, M.A.

University of Texas at Austin, May 2013

Supervisor: Carey King

56 pages, 72 references, 12 tables

This thesis examines the energy return on investment (EROI) of a model 3 MW hybrid gas-geothermal plant on the Texas Gulf Coast. The model plant uses a design similar to the DOE Pleasant Bayou No. 2 test geothermal plant, and uses a gas engine to harness entrained methane and an Organic Rankine Cycle turbine to harness thermal energy from hot brines. The indirect energy cost was calculated using the Carnegie Mellon University Economic Input-Output Life Environmental Life Cycle Analysis (EIO-LCA) model. The EROI of the plant using the 1997 EIO-LCA energy data is 12.40, and the EROI of the plant using 2002 EIO-LCA energy data is 14.18. Sensitivity analysis was run to determine how the plant parameters affect the EROI. A literature review of the EROI of different power sources shows that the EROI of the hybrid geothermal plant is greater than the EROI of flash steam geothermal and solar, but is lower than the EROI of dry steam geothermal, wind power, nuclear, coal, gas, and hydroelectric plants. An analysis of the EROI to financial return on investment (FROI) shows that the FROI for a hybrid geothermal plant could be competitive with wind and solar as a viable renewable resource in the Texas electricity market.

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Michael Richard Kanarek, M.S.Geo.Sci

University of Texas at Austin, August 2013

Supervisor: M. Bayani Cardenas

57 pages, 43 references, 4 tables

Moisture dynamics in the critical zone have significant implications for a variety of hydrologic processes, from water availability to plants, to infiltration and groundwater recharge rates. These processes are perturbed by events such as wildfires, which may have long-lasting impacts. In September 2011, the most destructive wildfire in Texas history occurred in and around Bastrop State Park, which was significantly affected; thus this is a rare opportunity to study soil moisture under such burned conditions. A 165 m long transect, bridging burned and unburned areas, was established within the “Lost Pines” of the park. Soil moisture was monitored using a variety of methods, including 2D electrical resistivity imaging (using dipole-dipole and Schlumberger configurations), handheld measurements using a ThetaProbe, and readings at depth using PR2 profile probes. Field measurements were collected at approximately one-month intervals to study temporal and seasonal effects on soil moisture. Greater soil moisture was found near the ground surface at the heavily burned end of the transect, where the majority of trees were killed by the fire and grasses now dominate, and lower near-surface soil moisture and higher resistivity at the opposite end of the transect, which is still populated by pine trees. These variations can likely be attributed to the vegetative variations between the two ends of the transect, with trees consuming more water at one end and the ground cover of grasses and mosses consuming less water and helping reduce evaporation at the burned end. Soil texture differences could also be a factor in greater soil moisture retention at the burned end of the transect. Given the higher moisture throughout the soil profile at the burned end of the transect, this could be an indication of greater infiltration, and could increase recharge, at least in the short term.

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Han Kyul Kim, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Timothy Shanahan

30 pages, 38 references

Lake Ossa, in western Cameroon, Africa (3°50' N, 9°36' E) records a sudden rainforest disruption around 2500 cal yr BP, as evident by pollen, sediment, and diatom changes recorded in a sediment core taken in the lake. The observed changes in biological and sedimentary properties have been used to support the notion that an abrupt climate change was responsible for this disruption event. However, the problem becomes more complex as humans are introduced into the picture. It has been found through archeological research that the Bantu, an iron-age people, migrated through the Lake Ossa region around the same period, deforesting large amounts of wood to smelt iron. To correctly discern the role of climate in this event, a climate proxy independent of surface processes must be introduced. In this project, average chain lengths of long n-alkanes from leaf waxes are used to show that the surficial changes far exceeded the impact of climate in the 2500 cal yr BP event.

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Masoumeh Kordi, Ph.D.

University of Texas at Austin, May 2013

Supervisors: William L. Fisher and Susan D. Hovorka

193 pages, 257 references, 7 tables

The effectiveness of CO2 injection in the subsurface for storage and EOR are controlled by reservoir quality variation. This study determines the depositional processes and diagenetic alterations affecting reservoir quality of the Lower Tuscaloosa Formation at Cranfield Field. It also determines the origin, time and processes of the grain-coating chlorite and its impacts on reservoir quality. Moreover, by integrating depositional and diagenetic characteristics and by linking them to sequence stratigraphy, the distribution of reservoir quality, could be predicted within a sequence stratigraphic framework.

The studied sandstones are composed of medium to coarse-grained, moderately sorted litharenite to sublitharenite with composition of Q76.1F0.4L23.5. Depositional environment of this formation in the Mississippi Interior Salt Basin is interpreted as incised-valley fluvial fill systems. The cross sections and maps at the field show trend of the sandy intervals within channels with a NW-SE paleocurrent direction.

During burial of the sandstones, different digenetic alterations including compaction, dissolution, replacement and cementation by chlorite, quartz, carbonate, kaolinite, titanium oxides, pyrite and iron-oxide modified the porosity and permeability. Among these, formation of chlorite coats plays the most important role in reservoir quality. The well-formed, thick and continuous chlorite coatings in the coarser grain sandstones inhibited formation of quartz overgrowth, resulted in high porosity and permeability after deep burial; whereas the finer grain sandstones with the poorly-formed, thin and discontinuous chlorite coatings have been cemented by quartz. The optimum amount of chlorite to prevent formation of quartz overgrowths is 6% of rock volume.

The chlorite coats are composed of two layers including the inner chlorite layer formed by transformation of the Fe-rich clay precursors (odinite) through mixed-layer clays (serpentine-chlorite) during early eodiagenesis and the outer layer formed by direct precipitation from pore waters through dissolution of ferromagnesian rock fragments during late eodiagenesis to early mesodiagenesis.

In the context of the reservoir quality prediction within sequence stratigraphic framework, the late LST and early TST are suitable for deposition of chlorite precursor clays, which by progressive burial during diagenesis could be transformed to chlorite, and thus results in preserving original porosity and permeability in deep burial.

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Ethan T. Lake, Ph.D.

University of Texas at Austin, May 2013

Supervisor: Mark Cloos

325 pages, 190 references, 8 tables

Explosive, caldera forming “super-eruptions” (an eruption of VEI 8 or larger, resulting in 1000+ km3 of volcanic ejecta in ignimbrite sheets) are the single most destructive natural disaster native to Earth. Super-eruptions require three elements to occur: 1-crustal magmatic fluxes above background solidification rates, 2-growth of a batholith scale magma chamber, and 3-an eruption trigger. This study addresses these requirements with new petrographic and geochemical analyses and numerical simulations of crustal magma bodies.

Crustal magmatic fluxes up to 10x steady-state arc rates are required to form volcanic provinces that host super-eruptions. Super-eruptions can occur in continental hot-spots or rift environments. Why arcs “flare-up” is the subject of active debate. Arcs may follow a regular cycle of lithospheric thickening, delamination, and asthenospheric upwelling (the Andean cycle); alternatively fertilized lithospheric mantle may undergo rapid melting. Targeted sampling (n = 165) of mapped but unsampled mafic and lamprophyric magmas in the San Juan magmatic locus of Colorado, an archetypical ignimbrite province, over three years identified both the lithospheric mantle reservoir and the most primitive San Juan magmas using optical petrography, whole rock geochemistry (n = 50) and Pb, Sr, and Nd isotope geochemistry (n = 32). These mafic magmas more closely resemble the continental lithosphere geochemically. Mixing models based on Energy Constrained Assimilation/Fractional-Crystallization (EC-AFC) indicate that the San Juan magmatism is the product of lithospheric melts and 30-40% crustal assimilation rather than asthenospheric upwelling. The Farallon flat-slab “pre-fluxed” and refrigerated the Colorado lithospheric mantle; removal of that slab at around 40 Ma triggered the SJVF “flare-up.”

Numerical simulations of crustal magma chamber growth indicate giant magma chambers form when high magma fluxes raise upper crustal temperatures to 300-400 °C at 5-10 km depth. These simulations focus on chamber growth, convection, and cooling at the expense of geometry or chamber mechanical failure with realistic sill-like geometry at the expense of thermal modeling. New 3D finite difference simulations emphasize the importance of geometry on chamber lifespan and crustal heating. A spherical chamber (i.e. model construct) requires 10x the cooling time of a 2km caldera footprint sill of same volume. Increasing sill thickness by 1km can double chamber longevity. Focused intrusions (i.e. 1D modeling) locally produce higher thermal gradients and preserve larger primary basalt volumes. Random intrusions in 3D yield basalt to crust ratios of 3-4:1 (required in the EC-AFC models). Random intrusion in 3D into the upper crust at “flare-up” fluxes (=10 km3 per k.y.) elevate average crustal geotherms by 10 °C / km, allowing for growth of batholithic scale magma chambers a wider footprint.

Once situated in the upper crust, sub-caldera magma chambers cool inward forming moving crystallization and fluid saturation fronts. If the saturation front propagates faster than the crystallization front, nucleating fluid bubbles have the opportunity to grow, ascend, and collect at the chamber roof. New 2D finite difference models couple magma chamber cooling to fluid production to explore the conditions of fluid escape and collection. Less silicic magma composition, equant geometry, high ambient thermal gradient, and a stock all aid in fluid pocket growth by slowing the advance of the crystallization front (a fluid trap) and triggering saturation at lower fluid concentrations. Fluid pockets that grow to certain sizes ( > 500 m hemispherical bubble) have the potential to trigger an eruption by propagation of a fluid fracture to the surface. This mechanism possibly triggered the eruption of the 5000+ km3 Fish Canyon Tuff as well as smaller, recent eruptions (Pinatubo, El Chichón).

Caldera forming super-eruptions occur in regions that meet these three requirements: 1-high magmatic flux, 2-rapid growth to batholithic size, and 3-a delayed eruption trigger. For the SJVF of Colorado melting of the “pre-fluxed” lithosphere provided the magmatic pulse which melted and heated the crust, forming a broad batholith. As magmatism peaked and began to wane, upper crustal magma chambers started to crystallize, exsolving fluids. These fluids ascended, collected, and fractured their way to the surface, triggering the Fish Canyon Tuff and other eruptions.

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Ryan Lester, PhD

University of Texas at Austin, May 2013

Supervisors: Kirk D. McIntosh and Luc L. Lavier

222 pages, 208 references, 3 tables

Arc-continent collisions are believed to be an important mechanism for the growth of continents. Taiwan is one of the modern day examples of this process, and as such, it is an ideal natural laboratories to investigate the uncertain behavior of continental crust during collision. The obliquity of collision between the northern South China Sea (SCS) rifted margin and Luzon arc in the Manila trench subduction zone allows for glimpses into different temporal stages of collision at different spatial locations, from the mature mountain-belt in central-northern Taiwan to the ‘pre-collision’ rifted margin and subduction zone south of Taiwan. Recently acquired seismic reflection and wide-angle seismic refraction data document the crustal-scale structure of the mountain belt through these different stages.

These data reveal a wide rifted margin near Taiwan with half-graben rift basins along the continental shelf and a broad distal margin consisting of highly-extended continental crust modified by post-rift magmatism. Magmatic features in the distal margin include sills in the post-rift sediments, intruded crust, and a high-velocity lower crustal layer that likely represents mafic magmatism. Post-rift magmatism may have been induced by thermal erosion of lithospheric mantle following break-up and the onset of seafloor spreading.

Geophysical profiles across the early-stage collision offshore southern Taiwan show evidence the thin crust of the distal margin is subducting at the Manila trench and structurally underplating the growing orogenic wedge ahead of the encroaching continental shelf. Subduction of the distal margin may induce a pre-collision flexural response along the continental shelf as suggested by a recently active major rift fault and a geodynamic model of collision. The weak rift faults may be inverted during the subsequent collision with the continental shelf. These findings support a multi-phase collision model where the early growth of the mountain belt is driven in part by underplating of the accretionary prism by crustal blocks from the distal margin. The wedge is subsequently uplift and deformed during a collision with the continental shelf that involves both thin-skinned and thick-skinned structural styles. This model highlights the importance of rifting styles on mountain-building.

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Mariya Levina, M.S.Geo.Sci.

University of Texas at Austin, May 2013

Supervisor: Brian K. Horton

100 pages, 54 references, 3 tables

Andean retroarc shortening associated with flattening of the Pampean segment of the subducting Nazca plate has resulted in a thin-skinned, east-directed thrust system that partitioned and uplifted Cenozoic foreland basin fill in the Precordillera of west-central Argentina. The temporal and kinematic evolution of the Precordillera fold-thrust belt can be approached through detailed analyses of the clastic sedimentary deposits now preserved in intermontane regions between major thrust faults. In this project, we focus on the uppermost Oligocene–Miocene basin fill exposed in the axial and eastern Precordillera along the San Juan River (Quebrada Albarracín and Pachaco regions) and western flank of the frontal structure (Sierra Talacasto). The nonmarine successions exposed in these regions record hinterland construction of the Frontal Cordillera, regional arc volcanism, and initial exhumation of the Precordillera thrust sheets.

Measured stratigraphic sections and lithofacies analyses of the preserved stratigraphic successions reveal initial development at ~24 Ma of an eolian depositional system influenced by regional volcanism and fluvial interactions, becoming a fully eolian system by 21-19 Ma. This system transitioned to a distributary fluvial system in which regions closer to the deformation front recorded sandy-gravelly braided stream sedimentation and regions farther east recorded more-distal floodplain-dominated deposition of thin-bedded mudstone and sandstone. The youngest sedimentary record is preserved in the Albarracin basin, a zone strongly influenced by explosive volcanism of nearby eruptive centers around 14 Ma, followed by a progradational alluvial-fan succession of pebbly, cross-stratified sandstone and thick, pebble to cobble conglomerate.

Provenance changes recorded by detrital zircon U-Pb age populations suggest that initial deformation in the Frontal Cordillera coincided with the early Miocene transition from eolian to fluvial deposition in the adjacent foreland basin. The overall upward coarsening nature of the fluvial succession and increased presence of Paleozoic clasts reflect the eastward progression of thin-skinned deformation in the Precordillera and resultant structural partitioning of the synorogenic foreland successions. Using apatite (U-Th)/He thermochronometry we are able to further constrain the age of uplift-induced exhumation and cooling of several Precordillera thrust sheets to 12-9 Ma. This apparent pulse of exhumation is evident in all three sections, suggesting rapid, large-scale exhumation by synchronous thrusting above a single décollement linking major structures of the eastern Precordillera.

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Reed Ahti Malin, M.A., M.PAff.

University of Texas at Austin, May 2013

Supervisor: Suzanne A Pierce

94 pages, 99 references, 1 table

In September 2009 exploratory testing of an old geothermal power well caused a blowout at the El Tatio geothermal field of northern Chile. El Tatio is the largest geyser field in the southern hemisphere. The blowout was a paradigm-shifting event for the management of the El Tatio geothermal field and drew attention to the disparity and critical nature of scientific information sharing.

This study uses the El Tatio incident as a case study for examining problems of common-pool resource management and geothermal energy development. It explores how differing valuations of geothermal resources resulted in a breakdown of coherent regulation and negative outcomes for all stakeholders. Contingent valuation methods were used to create an elicitive interview process in order to assess how differences in valuation drove these conflicts and negative outcomes. The sharing of scientific information through Decision Support Systems (DSS) is identified as an important element in resolving these conflicts and creating new policies for common-pool resource management.

These methods are presented as tools that can be used by stakeholders to find common ground and seek mutually beneficial outcomes. In addition, these tools can help with the critical issue of social perception of scientific data and science driven solutions to these problems. This study posits that the path forward is to ensure not only that scientific data is communicated in modes appropriate to the community and problem at hand, but that the acquisition and interpretation of this data is informed by stakeholder needs.

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Damian Markez, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisor: Lesli J. Wood

69 pages, 105 references

Recent drilling of deep stratigraphy in subsalt offshore Gulf of Mexico has revealed the presence of thick, amalgamated, Cretaceous siliciclastic reservoirs with the potential to become valid exploration targets. Similar to the Lower Tertiary deepwater play, the significant down-dip distance (› 400 km) from the source deltaics, the data gap across the modern structurally complex salt-tectonics-dominated slope and the difficulties of imaging subsalt stratigraphy pose challenges for the construction of meaningful deepwater system models to aid in exploration and appraisal efforts.

A 3D seismic dataset in the Mad Dog field at the basinward end of the modern allochthonous salt canopy and outboard of the Sigsbee Escarpment offers the opportunity to study the nature of the deep stratigraphy at central positions in the basin. The nature of the Cretaceous sedimentary system has been investigated through detailed structural and seismic geomorphologic mapping. An early syndepositional contractional event has been identified and temporally associated with Mesozoic emplacement of a deep salt sheet. These events are masked by the major Neogene-age phase of fold amplification that dominates the present-day subsalt structural framework. Ponded-basin deepwater sedimentation processes control early phases of deposition in the Cretaceous Mad Dog area and sediment-gravity flows are deposited as complexes of low sinuosity amalgamated channelized deposits in roughly-confined sediment pathways. Ponded fills show internal lateral accretion architectures that grow sigmoid in nature as the migrating systems interact with the approaching minibasin margins making evident the structural control on sediment architecture. Later phases of deposition are characterized by slightly sinuous feeder channels with multiple lobe development at their terminus. Variable directions of sediment source pathways indicate a linear-sourced slope apron depositional model for these systems. In addition to the more structured morphologic elements, there were also pervasive mass-transport processes active, presumably triggered by Mesozoic halokinesis. Data in sparse deep wells in the GoM that penetrate the Cretaceous suggest that the Late Cretaceous deepwater depositional system was composed of coarse-grained high density gravity flows. The geometries seen in seismic beneath the Mad Dog area support the existence of such a basinwardly extensive deepwater fan systems developed during the Cretaceous, and the low sinuosity channel geometries and small length:width ratio and amalgamated nature of fan lobes suggest that these systems may have indeed been high-density in nature.

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Adam Douglas Marsh, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisor: Timothy Rowe

333 pages, 308 references, 11 tables

Sarahsaurus aurifontanalis is the most recent sauropodomorph dinosaur to be discovered and named from the Early Jurassic of North America. The dinosaur is represented by a mostly complete and articulated holotype specimen that preserves a unique manual phalangeal count of 2-3-4-2-2 and accessory pubic foramen adjacent to the obturator foramen. The holotype of Sarahsaurus comprises a braincase and isolated cranial elements, but the skull previously referred to this taxon, MCZ 8893, can only be provisionally referred to Sarahsaurus until additional crania are found associated with postcranial material. Sarahsaurus comes from the middle third of the Kayenta Formation, which is considered to be Early Jurassic in age despite the absence of a radiometric date from that unit. A new technique used to obtain a U-Pb radiometric date from the type quarry of Sarahsaurus in the Kayenta Formation was influenced by secondary uranium enrichment in the open system of the fossil bone. That suggests that uranium within the Kayenta Formation may be the result of the movement of groundwater during the Laramide orogeny in the Late Cretaceous and Early Eocene, and lends support to the hypothesis that the uplift of the Colorado Plateau began relatively early in Late Cretaceous to the Eocene.

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Allison Marie Ned, MS Geo Sci

University of Texas at Austin, May 2013

Supervisors: Ronald J. Steel and Cornel Olariu

88 pages, 53 references, 2 tables

The sediment budget and paleogeography was reconstructed for the Maastrichtian fluvial to coastal plain Lance Formation (›200m thick) that developed coevally with the shoreline/shelf Fox Hills Sandstone (›200m thick) and deep-water Lewis Shale (›750m thick) in a complete source-to-sink system in the Washakie and Great Divide Basins of south central Wyoming. The system initiated during the final Western Interior Seaway (WIS) transgression and the onset of the Laramide Orogeny rapid subsidence (›2km in 1.9 My) that largely outpaced sediment flux into the basin so the system became and remained a deep-water (›500m water depth) basin beyond the Lance-Fox Hills shelf prism. The active tectonic setting and rapid subsidence caused the Lance fluvial and coastal plain deposits to aggrade and accumulate behind the generally rising shoreline trajectory of the Fox Hills Sandstone. The depositional succession is subdivided into 15 clinothem units and the Lance Formation is best exposed in outcrops in clinoforms 10, 11, and 12. Subsurface analysis correlates key stratigraphic surfaces across the basin to define the sediment budget and clinoform architecture. Field analysis along clinoform 12 on the east side of the basin details facies and paleohydraulic dimensions.

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John Alexandre Parker, M.S.Geo.Sci.

University of Texas at Austin, May 2013

Supervisor: Charles Kerans

130 pages, 54 references, 2 tables

Ooid grainstone reservoir architecture remains poorly understood, particularly because of sedimentologic and stratigraphic heterogeneities that are innate to grainstone body development. Understanding of Geospatial relationships and recovery of hydrocarbons from these significant reservoir facies can be improved with access to outcrop analog information from well exposed examples.

Object-based models and other modern subsurface reservoir models are considered superior methods for portraying realistic sediment distributions. These models, however, are highly dependent on input data describing sediment-body geometry for faithful template generation. Such input data are notably rare in carbonate systems. Maps generated from modern depositional patterns give a first approximation of areal distribution, but they are not as useful for understanding final preserved stratigraphic thickness and internal facies, sedimentary structure, and grain-type patterns. For this purpose, studies of exceptional outcrops are required. The 18 km long oblique-dip-oriented wall of the Shattuck Escarpment provides such a unique exposure of Permian-age grainstones.

The Shattuck Escarpment in the Guadalupe Mountains provides an oblique-dip profile that exposes a near-complete middle Permian Grayburg mixed clastic-carbonate shelf succession of three high-frequency sequences which contain 30 high-frequency cycles. Particularly important for this study are the four cycles that display full updip to downdip extents of ooid grainstone tidal bar and tidal delta objects. The data from the Shattuck wall presented in this paper focusses on the transgressive portion of the upper Grayburg, or G12 high-frequency sequence (HFS), located 5 km landward of the time-equivalent shelf margin. This interval is an analog for productive fields along the northwest shelf of the Delaware Basin and on the eastern flank of the Central Basin Platform. The goal of this project is to understand the sedimentology and facies/cycle architectural variability of tidally influenced shelf crest ooid grainstones of the Grayburg Formation. Comparing this outcrop data to modern grainstone deposits allows the reader to understand the small-scale and large-scale sedimentologic and architectural patterns in analogous subsurface ooid grainstone reservoirs.

Spatial analysis of these cycles was carried out using measured sections and GigaPan (high resolution photomosaic) data. Petrophysical (Porosity and Permeability) data was collected from three separate vertical core plug transects approximately 1 km apart with a vertical resolution of 30 cm. Cycle-set-scale grainstone complexes up to 6m thick extend at least 4.25 km along depositional dip and show variations in permeability between 6-400 mD and porosities between 8-20% within the lower portions of the grainstone complex.

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Laura Elizabeth Pommer, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisors: Julia Gale and Peter Eichhubl

292 pages, 110 references, 11 tables

In order to test the hypothesis that fractures in outcrops are equivalent to subsurface fracture systems I compare fracture cement morphology, texture, mineralogy and geochemistry from a suite of outcrop samples from Union Springs, NY, with fractures in four cores from a currently producing reservoir in southwest Pennsylvania. Transmitted light-microscope petrography and cold cathodoluminescence of calcite of outcrop and core samples reveals a variety of cement morphologies including crack-seal and blocky fracture cement textures that are interpreted as a record multiple repeated stages of fracture opening and sealing, as well as fibrous calcite fill and other mineral phases. The stable isotopic composition of calcite fracture cements from different fracture types in cores and outcrop range from -21.5 to +4.4‰δ13C PDB and -8.0 to -12.0 ‰ δ18O PDB and indicate calcite precipitation temperatures between 46 and 89°C. Fluid inclusion microthermometry from secondary fluid inclusions indicates trapping temperatures between 110 and 120°C. Microprobe analysis of fracture calcite cement indicates a range in Fe, Mn, and Mg composition, with subsurface and outcrop cement of similar composition. Assuming burial history predicts thermal history, isotopic compositions together with fluid inclusions suggest calcite precipitated in vertical fractures during prograde burial, during the Acadian to early Alleghanian orogenies. These findings indicate that fractures in outcrops of the Marcellus Formation can be used as a proxy for those in the subsurface.

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Timothy John Prather, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Jaime Barnes

34 pages, 28 references, 1 table

Volatile concentrations (Cl, H2O, and CO2) and stable isotope compositions (δD and δ37C1) of volcanic glasses (obsidians) have been determined to quantify the behavior of chlorine stable isotopes (35C1 and 37C1) during volcanic degassing. Pyroclastic obsidian clasts (n = 27), collected from tuff layers representing a single eruptive sequence that occurred circa 1350 A.D., as well as rhyolitic obsidian samples (n = 12) collected from the high-silica (‹70% Si) flows forming the domes and coulees in the region, were collected from the Mono Craters volcanic field, California. The Cl, H2O, and CO2 concentrations recorded by these eruptive air-fall obsidians track the chemical evolution of the magmatic system during eruption, whereas the concentrations of the dome samples represent the final degassed product. The H2O and CO2 concentrations of the air-fall samples range from 0.49 to 2.13 wt% and 2 to 35 ppm, respectively; whereas concentrations in the dome glasses range from 0.17 to 0.33 wt% and 1 to 3 ppm, respectively. H2O and CO2 concentrations in the air-fall samples and dome samples are strongly correlated and reflect the degassing trend of the eruptive sequence. Air-fall obsidians were selected from two tuff layers: 1) a lower layer containing average H2O and CO2 concentrations of 1.5 ± 0.4 wt% and 20 ± 7 ppm, respectively, and 2) an upper layer containing slightly lower average H2O and CO2 concentrations of 0.9 ± 0.4 wt% and 5 ± 3 ppm, respectively. Dome obsidians were selected from three rhyolitic flows in the region, Panum Crater Dome, North Coulee, and Northwestern Coulee, containing average H2O and CO2 concentrations of 0.27 ± 0.06 wt% and 2 ± 1 ppm, respectively. Chlorine concentrations of the air-fall samples range from 609 to 833 ppm and do not display a strong correlation with either H2O or CO2 concentrations. Chlorine concentrations are essentially identical between the two layers, averaging 746 ± 57 ppm m the lower layer and 703 ± 73 ppm in the upper layer.

δD values of the air-fall obsidians vary between -62 to -84‰ (lσ = ±2‰), whereas the dD values of the dome obsidians vary between -99 to -107‰, and display D/H ratios that decrease with lower total water content following a distillation trend dominated by open system degassing. δ37Cl values were measured on samples from each of the two tuff layers and from the domes. The samples from the lower layer have δ37Cl values between -2.0 to -0.1 ‰(n = 12), whereas the samples from the upper layer have δ37C1 values between -1.5 and -0.1‰ (n = 12) (la = ±0.2‰). δ37C1 values of domes samples range from -1.2 to 0.0‰ (n = 10). overlapping the range in δ37Cl values in the air-fall samples.

The lack of systematic correlation between the measured δ37C1 values and any of the other measured parameters (H2O, CO2, Cl concentrations, δD values) during the characteristic degassing sequence exhibited by the obsidian air-fall clasts and the dome obsidians indicates that chlorine stable isotopes likely do not fractionate during volcanic degassing. The wide range in δ37C1 composition may be indicative of heterogeneity of chlorine stable isotopes in the magma source.

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Caleb Hayes Rhatigan, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisor: Daniel Stockli

131 pages, 55 references

The northeast African continental margin of the Western Desert of Egypt is host to a complexly deformed series of Phanerozoic basins. Substantial sedimentary deposition (~5 km) and basin formation resulted from regional deformation due to continental colli¬sion and repeated rifting and inversion cycles. Limited sedimentary exposure and explora¬tion has prevented elucidation of Phanerozoic basin evolution, particularly in the Paleozoic. Previous studies of the region have largely relied upon sedimentary analysis, gravity, and 2D/3D seismic data. This study, in contrast, has employed extensive use of detrital zircon (U-Th)/He thermochronology (n=1004) from 17 wells in conjunction with 3D seismic, well log correlation, and heat flow data to elucidate a spatiotemporally comprehensive tectonic and stratigraphic model.

The detrital zircon thermochronometric data provides new evidence that the lower Paleozoic, Carboniferous, and Mesozoic stratigraphic sequences of the Western Desert represent thermally distinct, tectonically controlled sequences with independent thermal evolutions. The lower Paleozoic sequence has been partially thermally reset, reaching temperatures of ~140-170°C. Partial resetting is noted throughout the region and reached its thermal maximum in the Permo-Triassic, synchronous with onset of Neotethyan rifting. The Carboniferous sequence has not been thermally reset, with exposure to temperatures no greater than ~140°C and reaching thermal maximum presently. Carboniferous (U-Th)/He ages have dominant input from short-lag-time zircons (exhumation to deposition) and indicate the stratigraphic sequence was proximally sourced. The proximal sourcing is likely from transmitted stress and fault reactivation in Egypt during the Hercynian Oroge¬ny that caused fault block exhumation and erosional unroofing. Sediment was shed from uplifted fault blocks that formed the eastern boundary of the Carboniferous sequence. The Mesozoic sequence has not been thermally reset, reaching temperatures no greater than ~120°C and presently reaching thermal maximum.

Localized areas with stacking of lower Paleozoic, Carboniferous, and Mesozoic sequences likely bury the lower Paleozoic to abnormally deep depths (~7 km) and elevated temperatures of ~200°C. Evidence from faulting relationships, basin controlling structures, and heat flow data indicate that N-S trending basement structures may define a region of crustal transition between the Archean-Paleoproterozoic Saharan Metacraton and the juvenile Arabian-Nubian Shield.

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John Burnham Shaw, Ph.D.

University of Texas at Austin, May 2013

Supervisor: David Mohrig

170 pages, 160 references, 8 tables

The Wax Lake Delta (WLD) is a sandy, modern river delta prograding rapidly into Atchafalaya Bay. This dissertation uses field data to improve the understanding of channel kinematics that dictate river delta geometry and stratigraphy, while providing a framework for coastal restoration efforts. The studies presented here show that the distributary channel network of the WLD is erosional. In the first study, analyses of the feeder channel to the WLD and the channel network within the sub-aerially emergent delta show that the channel bed has incised into the consolidated muds that act as bedrock. The large (>62%) fraction of bedrock exposure found in multi-beam surveys is related to the under-saturation of suspended sand measured during the flood of 2009. The second study concerns the delta front beyond the emergent delta Distributary channels extend 2 – 6 km into the delta front. Four bathymetric surveys of one bifurcating distributary channel – Gadwall Pass – show that the majority of bed aggradation occurs during floods, but significant channel extension of each bifurcate channel occurs during low river discharge. In the third study, field measurements of fluid flow during a tidal cycle indicate that tidal augmentation of during periods of low river discharge is responsible for channel extension during low river discharges. Flow direction measured from streaklines present in aerial photomosaics is combined with bathymetric evolution data to quantify spatial velocity changes on the delta front. These data show that flow spreading is insufficient to prevent acceleration at channel margins, providing an explanation for observed erosion. Flow divergence is limited on the delta front by the proximity of neighboring channels, even though they are separated by 10-30 channel widths. The associated convergence of flow in inter-distributary bays occurs along “drainage troughs”. These channel-forms collect flow that has been dispensed from distributary channel network. Finally, ambient currents in Atchafalaya Bay (0.06 – 0.2 m s-1) caused by tides and the proximity to the neighboring Atchafalaya Delta appear to alter flow patterns on the delta foreset, and are responsible for channel curvature on the delta front.

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Benjamin O'Gorman Sigrin, M.A., MPAff.

University of Texas at Austin, May 2013

Supervisors: Varun Rai and Jay Zarnikau

66 pages, 79 references, 13 tables

Diffusion of microgeneration technologies, particularly rooftop photovoltaic (PV), represents a key option in reducing emissions in the residential sector. This thesis uses a uniquely rich dataset from the burgeoning residential PV market in Texas to study the nature of the consumer's decision-making process in the adoption of these technologies. Focusing on the financial metrics and the information decision makers use to base their decisions upon, I study how the leasing and buying models affect individual choices and, thereby, the adoption of capital-intensive energy technologies.

Overall, the leasing model is found to more effectively address consumers' informational requirements. Contrary to previous studies, buyers and lessees of PV are not found to substantially differ along socio-demographic variables, though they do differ significantly along cash availability, levels of environmental concern, and relative importance of financial aspects. Instead, the leasing model has opened up the residential PV market to a new, and potentially very large, consumer segment—those with a tight cash flow situation.

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Isaac Blaine Smith, Ph.D. Geological Sciences

University of Texas at Austin, August 2013

Supervisor: John W. Holt

168 pages, 131 references, 3 tables

The north and south polar layered deposits (NPLD and SPLD respectively) of Mars are 2 - 3 km thick and mostly ice, comprising nearly all of the known water reserves on Mars. They are commonly believed to hold a detailed record of recent (~ 10 - 100 Myr) climate within their layers. Dominating the surface of the NPLD, intriguing spiral depressions called troughs, exhibit a pinwheel appearance.

In late 2006, the Shallow Radar (SHARAD) instrument began making observations. SHARAD can detect internal structure within the PLD, making observations that are impossible with instruments that only inspect the surface. SHARAD data reveals a unique stratigraphic record associated with trough formation and migration. The troughs did not exist during deposition of the first half of NPLD accumulation but initiated some 1000 m below the current surface and have migrated as much as 100 km northward. Three processes are responsible for this migration: wind transport, insolation induced sublimation, and atmospheric deposition.

I synthesize work from ground penetrating radar, optical imagery, established analogs, and atmospheric modeling in order to derive a process model that describes trough formation and evolution, including migration. The NPLD spiral troughs belong to a larger classification of features called cyclic steps, which can exist in either erosional or depositional environments. On the SPLD, troughs and a variety of other features exist. While SPLD features are more complex than NPLD troughs, they exist due to the same three processes.

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Pamela Ann Speciale, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Elizabeth Catlos

82 pages, 83 references, 8 tables

The Beypazari granitoid was emplaced in a Late Cretaceous volcanic arc in north central Turkey. This pluton crops out north of a major tectonic suture and provides important evidence for processes that occurred during the closure of the Neo-Tethys Ocean. A generally accepted tectonic model for emplacement is northward subduction of Neo-Tethyan oceanic lithosphere beneath Laurasia. This study presents new geochemical and geochronological analyses of the pluton, including the first U-Pb zircon ages and the first cathodoluminescence (CL) images used to interpret ages from the Beypazari granitoid. Analyses reveal a geochemically heterogeneous granitoid, with mafic enclaves and aplite dikes. Zircons from its northern granodiorite and quartz monzonite exposure dated in rock thin section are 95.4±4.2 Ma to 51.5±2.2 Ma (238U/206Pb, ±lσ) and display characteristic igneous zoning in CL. Its oldest Late Cretaceous ages likely time crystallization, but inspection of younger Paleocene and Eocene grains in composite CL-secondary electron images show they are located along grain boundaries surrounded by alteration textures and were affected by fluid-driven metamorphism. Ages between the extremes were often obtained from zircon mid-rims and likely time continuous crystallization until -70 Ma. Zircons from an aplite dike are Paleocene to Pliocene. In CL, its two youngest zircons (5.6±0.3 Ma and 5.0±0.3 Ma) show evidence of fluid alteration and recrystallization, but could possibly time a transition in the region to extrusional tectonics. The Beypazari zircon ages overlap with those from the Sivrihisar granitoid located ~70 km south, suggesting they share parts of a common tectonomagmatic history. This study presents a model for their development wherein subduction and break off of two major slabs induce asthenospheric melts and are the cause of protracted zircon crystallization. Evidence for these processes is revealed in recent teleseismic mantle tomography studies showing fast seismic anomalies below the 660 km discontinuity beneath the Sakarya, Tavsanli and Afyon zones, and interpreted as possible remnants of detached slab(s) or delaminated lithosphere.

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Yanadet Sripanich, Bachelor of Science

University of Texas at Austin, May 2013

Supervisor: Sergey B. Fomel

56 pages, 27 references, 8 tables

I propose an efficient algorithm for two-point seismic ray tracing in layered media by means of the bending method based on Fermat's principle of stationary traveltime. The algorithm uses the fact that the matrix of the second derivatives of traveltime function with respect to the points of intersection at the interfaces has a blocked tridiagonal structure. This feature allows me to easily invert the matrix via a series of recursive steps, which leads to a fast implementation of the Newton-Raphson method to efficiently solve for a raypath with stationary traveltime. To demonstrate accuracy of the proposed algorithm, I compare results computed from the algorithm to those from analytical solutions. I conduct Kirchhoff modeling in layered medium as an example of possible applications of the developed algorithm.

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Michelle Renae Stocker, Ph.D.

University of Texas at Austin, May 2013

Supervisor: Christopher J. Bell

297 pages, 375 references

Conceptualizations of actual biological patterns as preserved in the fossil record must accommodate the results of biotic and abiotic drivers of faunal dynamics. However, those conceptualizations also may reflect cognitive biases resulting from foundational philosophical stances. Whether fossils are conceptualized as the remains of biological entities or as geological objects will affect both taxonomic identifications and secondary inferences derived from those identifications. In addition, operational research bias centered on relativistic views of ‘importance’ of particular components (i.e., taxonomic or skeletal region) of the assemblage results in preferential documentation of some taxa and marginalization of others. I explored the consequences of those specific cognitive and operational biases through examination of Triassic and Eocene faunal assemblages in western North America. For the Triassic I focused on taxonomic and systematic treatments of Paleorhinus, a group of phytosaurs important for the establishment of biochronologic correlations. Specimen-level reexamination of Paleorhinus supported a restricted usage of Paleorhinus as a clade, dissolved a biochronologic connection between terrestrial and marine deposits, and indicated a prior compression of the early part of the Late Triassic as a result of previous conceptualizations of species. I reexamined the Otis Chalk tetrapod assemblage in light of new specimens and modern phylogenetic frameworks. My examination supported a restricted usage of the Otischalkian for biochronologic correlation of the Late Triassic, and emphasized the importance of apomorphic character-based specimen examinations in conjunction with detailed lithostratigraphy prior to the development of biochronologic schema. For the Eocene I focused on undocumented terrestrial reptiles from the late Uintan fauna of West Texas. Specifically I discovered new taxa and new geographic occurrences of amphisbaenians and caimanine crocodylians. The amphisbaenians represent the southernmost record of the clade in the North American Paleogene, and, when combined with other amphisbaenian records, document that the clade responded to late Paleogene climatic changes in ways different from the inferred mammalian response. The new taxon of caimanine crocodylian represents a new geographic and temporal record of that clade. That new record indicates that the biogeographic range of extant caimans represents a climate-driven restriction from a formerly more expansive range, and suggests that the previous geographic and temporal gap in paleodistribution data is related to sampling biases and is not a solely a biological phenomenon. These data indicate that reliable characterization of vertebrate faunal dynamics requires open acknowledgment and appropriate documentation of cognitive and operational biases that affect interpretations of paleontological data.

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Ying Sun, Ph.D.

University of Texas at Austin, May 2013

Supervisor: Robert E. Dickinson

185 pages, 215 references, 6 tables

Reliable prediction of climate change and its impact on and feedbacks from terrestrial carbon cycles requires realistic representation of physiological and ecological processes in coupled climate-carbon models. This is hampered by various deficiencies in model structures and parameters. The goal of my study is to improve model realism by incorporating latest advances of fundamental eco-physiological processes and further to use such improved models to investigate climate-carbon interactions at regional to global scales. I focus on the CO2 diffusion within leaves (a key plant physiological process) and large-scale disturbances (a fundamental ecological process) as extremely important but not yet in current models.

The CO2 diffusion within plant leaves is characterized by mesophyll conductance (gm), which strongly influences photosynthesis. I developed a gm model by synthesizing new advances in plant-physiological studies and incorporated this model into the Community Land Model (CLM), a state-of-art climate-carbon model. I updated associated photosynthetic parameters based on a large dataset of leaf gas exchange measurements. Major findings are: (1) omission of gm underestimates the maximum carboxylation rate and distorts its relationships with other parameters, leading to an incomplete understanding of leaf-level photosynthesis machinery; (2) proper representation of gm is necessary for climate-carbon models to realistically predict carbon fluxes and their responsiveness to CO2 fertilization; (3) fine tuning of parameters may compensate for model structural errors in contemporary simulations but introduce large biases in future predictions. Further, I have corrected a numerical deficiency of CLM in its calculation of carbon/water fluxes, which otherwise can bias model simulations.

Large-scale disturbances of terrestrial ecosystems strongly affect their carbon sink strength. To provide insights for modeling these processes, I used satellite products to examine the temporal-spatial patterns of greenness after a massive ice storm. I found that the greenness of impacted vegetation recovered rapidly, especially in lightly and severely impacted regions. The slowest rebound occurred over moderately impacted areas. This nonlinear pattern was caused by an integrated effect of natural regrowth and human interventions.

My results demonstrate mechanisms by which terrestrial carbon sinks could be significantly affected and help determine how these sinks will behave and so affect future climate.

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Lindsey A. Sydow, M.S. Geo. Sci.

University of Texas at Austin, August 2013

Supervisor: Philip C. Bennett

103 pages, 40 references, 13 tables

One chemoautotrophic origin of life theory posits the abiotic formation of alkyl thiols as an initial step to forming biomolecules and eventually a simple chemoautotrophic cell. The premise of this theory is that a recurring reaction on the charged surfaces of pyrite served as a primordial metabolism analogous to the reductive acetyl-CoA pathway (Wächtershäuser 1988) that was later enveloped by a primitive cellular membrane. Alkyl thiols have not previously been identified in terrestrial hot springs as unequivocally abiogenic, but they have been produced in the laboratory under hydrothermal conditions in the presence of a catalyst.

I analyzed the dissolved gas content of several hot springs and conducted sterile laboratory experiments in order to evaluate the abiogenic formation of methanethiol (CH3SH), the simplest of the alkyl thiols. Specifically of interest was Cinder Pool, an acid-sulfate-chloride hot spring in Yellowstone National Park. This spring is unusual in that it contains a subaqueous molten sulfur layer (~18 m depth) and thousands of iron-sulfur-spherules floating on the surface, which are created by gas bubbling through the molten floor of the spring. This material could potentially serve as a reactive and catalytic surface for abiogenic CH3SH formation in Cinder Pool.

Gas samples were collected from Cinder Pool and an adjacent hydrothermal feature in fall of 2011 using the bubble strip method. Two samples contained measurable quantities of CH3SH and other organic sulfur gases, with concentrations of all gases generally higher at the bottom of the pool. Laboratory microcosm experiments were conducted to replicate these findings in a sterile environment. Analog Cinder Pool water was injected into serum bottles containing different iron-sulfur compounds, including cinders collected from the pool itself, as catalytic surfaces for the CH3SH generating reaction. The bottles were then charged with hydrogen (H2), carbon dioxide (CO2), and carbon disulfide (CS2) as reaction gases and incubated for a week at temperatures between 60 and 100°C. Bottles used either powdered FeS, FeS2 (pyrite) or cinder material as a catalytic surface, and all of these surfaces were capable of catalyzing CH3SH formation. In bottles without imposed CS2, however, cinder material was the only surface that produced any detectable CH3SH.

While CH3SH is central to the autotroph-first theory and has been synthesized in the laboratory (e.g. Heinen and Lauwers 1996), it has not previously been observed to form abiotically in natural systems. I have identified CH3SH in a natural hydrothermal feature where it is unlikely to have formed secondary to microbial activity, and I have duplicated these field findings in sterile laboratory experiments using the cinders as a reactive surface for formation.

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Marin Cherise Trautman, M.S. Geo. Sci.

University of Texas at Austin, August 2013

Supervisor: Mark Cloos

336 pages, 70 references, 12 tables

The Ertsberg-Grasberg Mining District of Papua, Indonesia (Western New Guinea) hosts the Ertsberg Cu-Au Skarn, the giant Grasberg Porphyry Cu-Au deposit, and several other orebodies. Two 1700-meter-long cores beneath the Kucing Liar ore skarn (KL98-10-22) and the Grasberg Igneous Complex (KL98-10-21) contain high concentrations of vein and disseminated molybdenite. KL98-10-22, the focus of this study, intersects two previously unencountered intrusions, the “Tertiary intrusion Kucing Liar” (Tikl) and “Tertiary Pliocene intrusion” (Tpi). An intense dilatational quartz vein stockwork cuts Tikl and Ekmai Sandstone (Kkes) units, predating Tpi intrusion. Prior to these ultradeep cores, which extend almost 3 km below pre-mining surface, molybdenite was rarely observed in the district.

Geochemistry and isotopic data indicate that Tikl and Tpi intrusions originated from the same large magmatic system that emplaced other ore-forming Ertsberg-Grasberg district intrusions. Magma in a lower crustal chamber was recharged at least twice, according to Sr-Nd data. Laser-ablation inductively-coupled plasma mass spectrometry of magmatic zircons yields 238U-206Pb ages between 3.40 ± 0.12 Ma (Dalam Andesite) and 2.77 ± 0.15 Ma (Ertsberg intrusion), revealing a shorter period of igneous activity than previously measured by K-Ar and Ar-Ar dating. Analyses include composite ages of 3.28 ± 0.08 Ma for Tikl and 3.18 ± 0.11 Ma for Tpi. Inherited zircon cores indicate Precambrian (mostly Proterozoic) basement.

Molybdenite veining beneath the Kucing Liar Skarn and Grasberg Igneous Complex postdates stockwork veining and occurred before the 2.99 ± 0.11 Ma Kali dikes. Only one molybdenite vein was observed cutting Tpi. Molybdenites yielded ~3 Ma Re-Os ages and anomalous ›4 Ma and ‹0.5 Ma ages; anomalous ages were not reproducible in follow-up analyses (this study). Smearing deformation of molybdenite (through fault activity) causes crystal strain, likely leading to annealing recrystallization. Recrystallization possibly redistributes daughter-product Os, resulting in anomalous ages from annealed material. Fluids with high Mo/Cu ratios (which were likely supercritical) precipitated late-stage molybdenite deep in the system. These fluids developed through magma chamber crystallization, which concentrated molybdenum in the melt as an incompatible element, and stripping of Cu from the magma chamber during hydrothermal activity.

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Natasha Slonim Vitek, M.S.

University of Texas at Austin, May 2013

Supervisor: Christopher J. Bell

156 pages, 95 references, 16 tables

Variation is a key component of the evolutionary process. However, variation often is poorly understood within species. The eastern box turtle (Terrapene carolina) presents an excellent opportunity to study that topic because extant populations have high levels of variation in soft-tissue characters as well as morphological variation in skeletal characters. To explore patterns of spatiotemporal variation, I used geometric morphometrics to quantify shape within three datasets. First, I asked to what extent size explained total shape variation using an ontogenetic series of 101 specimens. Next, I examined to what extent subspecies were morphologically distinct and identifiable in the modern record, and to what degree they explained overall variation using a dataset of 200 modern specimens. Finally, I compared the patterns in the modern biota to those from the fossil record using the previous datasets as well as a fossil dataset of 44 Pleistocene shells of T. carolina.

I found that in four views of the turtle shell (dorsal, ventral, posterior, and lateral), size significantly explains 10% - 31% of the variation in shape. Some of the characters correlated with size were historically ascribed to characters of subspecies. Studying the extent to which size explains overall variation in different subsamples of my data allowed me to discover a new way of classifying segments of a population in order to account for size in future studies. Subspecies identification also explained a statistically significant amount of overall shape variation. However, the results of assignments tests and CVAs indicated insignificant or unreliable differences. Results indicate that differences between putative subspecies are more statistically significant than they are biologically significant. They do not support the recognition of subspecies in T. carolina. The inability of statistical analyses to identify individuals of a subspecies based on shell shape means that subspecies cannot be identified in the fossil record. Some of the same relationships between shape and size are present in the fossil record and the modern biota, but other morphological patterns are unique to fossil specimens. Two of the morphotypes co-occur in the same strata, and represent a unique evolutionary pattern not seen in the modern biota.

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Kerstan Josef Wallace, M.S.Geo.Sci.

University of Texas at Austin, May 2013

Supervisors: Timothy A. Meckel and Michael H. Young

137 pages, 75 references, 4 tables

Geologic sequestration has been suggested as a viable method for greenhouse gas emission reduction. Regional studies of CO2 storage capacity are used to estimate available storage, yet little work has been done to tie site specific results to regional estimates. In this study, a 9,258,880 acre (37469.4 km2) area of the coastal and offshore Texas Miocene interval is evaluated for CO2 storage capacity using a static volumetric approach, which is essentially a discounted a pore volume calculation. Capacity is calculated for the Miocene interval above overpressure depth and below depths where CO2 is not supercritical. The goal of this study is to determine the effectiveness of such a regional capacity assessment, by performing refinement techniques that include simple analytical and complex reservoir injection simulations. Initial refinement of regional estimates is performed through net sand picking which is used instead of the gross thickness assumed in the standard regional calculation. The efficiency factor is recalculated to exclude net-to-gross considerations, and a net storage capacity estimate is calculated.

Initial reservoir-scale refinement is performed by simulating injection into a seismically mapped saline reservoir, near San Luis Pass. The refinement uses a simplified analytical solution that solves for pressure and fluid front evolution through time (Jain and Bryant, 2011). Porosity, permeability, and irreducible water saturation are varied to generate model runs for 6,206 samples populated using data from the Atlas of Northern Gulf of Mexico Gas and Oil Reservoirs (Seni, 2006).

As a final refinement step, a 3D dynamic model mesh is generated. Nine model cases are generated for homogeneous, statistically heterogeneous, and seismic-based heterogeneous meshes to observe the effect of various geologic parameters on injection capacity.

We observe downward revisions (decreases) in total capacity estimation with increasingly refined geologic data and scale. Results show that estimates of storage capacity can decrease significantly (by as much as 88%) for the single geologic setting investigated. Though this decrease depends on the criteria used for capacity comparison and varies within a given region, it serves to illustrate the potential overestimation of regional capacity assessments compared to estimates that include additional geologic complexity at the reservoir scale.

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Kai Wang, M.S.Geo.Sci.

University of Texas at Austin, August 2013

Supervisor: Robert E. Dickinson

56 pages, 59 references, 1 table

Land surface covers only 30% of the global surface, but contributes largely to the intricacy of the climate system by exchanging water and energy with the overlying atmosphere. The partitioning of incident solar radiation among various components at the land surface, especially vegetation and underlying soil, determines the energy absorbed by vegetation, evapotranspiration, partitioning between surface sensible and latent heat fluxes, and the energy and water exchange between the land surface and the atmosphere. Because of its significance in climate model, land surface model solar radiation partitioning scheme should be evaluated in order to ensure its accuracy in reproducing these naturally complicated processes. However, few studies evaluated this part of climate model. This study examines a land surface solar radiation partitioning scheme, i.e., that of the Community Land Model version 4 (CLM4) with coupled carbon and nitrogen cycles.

Taking advantage of multiple remote sensing fraction of absorbed photosynthetically active radiation (FPAR) datasets, ground observations and a unique 28-year FPAR dataset derived from the Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) dataset, we evaluated the CLM4 FPAR’s seasonal cycle, diurnal cycle, long-term trends and spatial patterns. Our findings show the model roughly agrees with observations in the seasonal cycle , long-tern trend and spatial patterns but does not reproduce the diurnal cycle. Discrepancies also exist in seasonality magnitudes, peak value months and spatial heterogeneity. We identified the discrepancy in the diurnal cycle as due to the absence of dependence on sun angle in the model. Implementation of sun angle dependence in a one-dimensional (1-D) model is proposed. The need for better relating vegetation to climate in the model indicated by long-term trends is also noted. Evaluation of the CLM4 land surface solar radiation partitioning scheme using remote sensing and site level FPAR datasets provides targets for future development in its representation of this naturally complicated process.

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Travis Zhi-Rong Wicks, M.S. Geo. Sci.

University of Texas at Austin, May 2013

Supervisors: Timothy M. Shanahan and Christopher J. Bell

94 pages, 91 references, 5 tables

Records of change of δ13C values in vertebrate teeth offer an opportunity to gain insight into changes in past vegetation. Increasingly, teeth from small mammals are used for such purposes, but because their teeth grow very rapidly, seasonal changes in vegetation potentially provide a large source of variability in carbon isotope composition, complicating interpretations of small mammal tooth isotope data. To investigate the controls of seasonality on the stable isotope composition of fossil teeth, we constructed a Monte-Carlo-based model to simulate the effects of changes in the seasonal pattern of diet in leporid lagomorphs (rabbits and hares) on the distribution of δ13C values in random populations of leporid teeth from the Edwards Plateau in central Texas. Changes in mean-state, seasonal vegetation range, and relative season length manifest themselves in predictable ways in the median, standard deviation, and skewness of simulated tooth δ13C populations, provided sufficient numbers of teeth are analyzed. This Monte Carlo model was applied to the interpretation of a 20,000 year record of leporid tooth δ13C values from Hall’s Cave on the Edwards Plateau in central Texas. Variations in the δ13C values of teeth deposited at the same time (standard deviation = 1.69‰) are larger than changes in the mean vegetation composition reconstructed from bulk organic carbon δ13C, indicating the influence of short-term variability, making it difficult to assess changes in mean C3/C4 vegetation from the tooth δ13C data. However, populations of teeth from different climate intervals (e.g., the late Glacial, Younger Dryas, and the Holocene) display changes in the shape of the tooth δ13C distributions. Interpretation of these changes as shifts in seasonal vegetation patterns that are based upon results from our model are consistent with hypothesized climatic changes. An increase in the standard deviation of the tooth population between the late Glacial and the Younger Dryas – Holocene is consistent with an increase in seasonality. Furthermore, a shift to more C3-dominated vegetation in the tooth δ13C distribution during the Younger Dryas is accompanied by a more skewed population – indicative of not only wetter conditions but an increase in the duration in the C3 growing season. However, late Holocene changes in vegetation are not clear in the tooth data, despite the evidence from bulk organic carbon δ13C values for an increase in % C3 vegetation of 57%. Small mammal teeth can potentially provide unique insights into climate and vegetation on seasonal and longer timescales that complement other data, but should be interpreted with a careful consideration of local conditions, taxon ecology and physiology, and the dominant timescales of isotope variability.

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Corinne Wong, PhD

University of Texas at Austin, August 2013

Supervisor: Jay L. Banner

226 pages, 249 references, 21 tables

There is a strong concern about how water resources will be affected by future climate change. Investigation of how a hydrologic system might respond to climate change, however, requires a detailed understanding of the controls on and factors that might affect that system. The research presented in this dissertation focuses on improving the understanding of the Barton Springs segment of the Edwards aquifer in central Texas. The first three chapters of this dissertation present research investigating spatial and temporal controls on groundwater geochemistry. The fourth chapter focuses on characterizing and understanding the controls on long-term hydrologic variability by reconstructing past climate from a speleothem (cave mineral deposit) collected from a central Texas cave. On spatial scales, Edwards aquifer groundwater geochemistry is influenced by water-rock interaction (calcite and dolomite recrystallization, gypsum dissolution, and calcite precipitation) and mixing between fresh groundwater and saline groundwater. On temporal scales, variation in groundwater geochemistry is dictated by the extent to which fresh groundwater mixes with recharging stream water. The degree of mixing is sensitive to changes in climate conditions (i.e., more mixing under wetter conditions) and type of flow path (i.e., conduit or diffuse) that dominantly supplies a given site. The geochemistry of stream water, which provides the majority of recharge to the aquifer, is degrading over time and indirectly controlled by anthropogenic sources under both wet and dry conditions. Climate reconstructed from a speleothem suggests that central Texas moisture conditions were relatively constant from the mid to late Holocene (0 to 7 ka), except for an extended dry interval from 0.5 to 1.5 ka. Speleothem δ18O values spike during this dry interval, suggesting that decreases in Pacific-derived moisture or decreased tropical storm activity might have been coincident with the prolonged dry interval. This research has improved understanding of the natural variability of and controls on physical and geochemical components of hydrologic system in central Texas.

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Stephanie Grace Wood, M.S. Geo. Sci.

University of Texas at Austin, August 2013

Supervisors: Stephen C. Ruppel and Robert G. Loucks

259 pages, 189 references, 9 tables

The Pennsylvanian Marble Falls Formation in the Llano Uplift region of the southern Fort Worth Basin (Central Texas) is a Morrowan-Atokan mixed carbonate-siliciclastic unit whose deposition was influenced by icehouse glacioeustatic sea-level fluctuations and foreland basin tectonics. Previous interpretations of the Marble Falls Formation focused on outcrop data at the fringes of the Llano Uplift. This study uses a series of 21 cores to create a facies architectural model, depositional environmental interpretation, and regional sequence stratigraphic framework. On the basis of core data, the study area is interpreted to have been deposited in a ramp setting with a shallower water upper ramp area to the south and a deeper water basin setting to the north. Analysis of cores and thin sections identified 14 inner ramp to basin facies. Dominant facies are: (1) burrowed sponge spicule packstone, (2) algal grain-dominated packstone to grainstone, (3) skeletal foraminiferal wackestone, and (4) argillaceous mudstone to clay shale.

Facies stacking patterns were correlated and combined with chemostratigraphic data to improve interpretations of the unit’s depositional history and form an integrated regional model.

The Marble Falls section was deposited during Pennsylvanian icehouse times in a part of the Fort Worth Basin with active horst and graben structures developing in response to the Ouachita Orogeny. The resulting depositional cycles reflect high-frequency sea-level fluctuations and are divided into 3 sequences. Sequence 1 represents aggradational ramp deposition truncated by a major glacioeustatic sea-level fall near the Morrowan-Atokan boundary (SB1). This fall shifted accommodation basinward and previously distal areas were sites of carbonate HST in Sequence 2 deposition following a short TST phase. Sequence 3 represents the final phase of carbonate accumulation that was diachronously drowned by Smithwick siliciclastics enhanced by horst and graben faulting.

These findings contribute to our understanding of the depositional response to glacioeustatic sea-level changes during the Pennsylvanian and can also form the basis for constructing a sedimentological and facies analog for Morrowan to Atokan shallow- to deepwater carbonates in the Permian Basin and the northern Fort Worth Basin.

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Yu Xia, M.S. Geo. Sci.

University of Texas at Austin, August 2013

Supervisor: Stephen P Grand

60 pages, 43 references

The Western U.S. has experienced widespread extension during the past 10’s of millions of years, largely within the Basin and Range and Rio Grande Rift provinces. Tomography results from previous studies revealed narrow fast seismic velocity anomalies in the mantle on either side of the Rio Grande Rift as well as at the western edge of the Colorado Plateau. The fast mantle anomalies have been interpreted as down-welling that is part of small scale mantle convection at the edge of extending provinces. It was also found that crust was thicker than average above the possible mantle down-welling, indicating that mantle dynamics may influence crustal flow. We present results from P/S conversion receiver functions using SIEDCAR (Seismic Investigation of Edge Driven Convection Associated with the Rio Grande Rift) data to determine crustal and lithospheric structure beneath the east flank of the Rio Grande Rift. Crustal and lithosphere thickness are estimated using P-to-S and S-to-P receiver functions respectively. Receiver function migration methods were applied to produce images of the crust and lithosphere. The results show variable crustal thickness through the region with an average thickness of 45 km. The crust achieves its maximum thickness of 60km at 105W longitude, between 33.5N and 32.2N latitude. This observation confirms previous receiver function results from Wilson, et al., 2005. Body wave tomography (Rocket, 2011; Schmandt and Humphreys, 2010) using similar data to what we used for the receiver function analysis, shows mantle downwelling closely associated with the thickened crust. We believe that the thickened crust might be due to lower crustal flow associated with mantle downwelling or mantle delamination at the edge of the Rio Grande Rift. In this model the sinking mantle pulls the crust downward causing a pressure gradient within the crust thus causing the flow. Our S-P images show signal from the lithosphere-asthenosphere boundary (LAB) with an average LAB thickness of 100 km but with a sharp transition at about 105° W from 75 km to over 100 km. The region with abnormally thick crust overlies a region where the lithosphere appears to have a break. We interpret our results as showing that lower lithosphere has and is delaminating near the edge of the Great Plains accompanied by lower crustal flow in some places determined by lower crustal viscosity.

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Yao You, Ph.D.

University of Texas at Austin, December 2013

Supervisors: Peter Flemings and David Mohrig

129 pages, 67 references, 3 tables

Submarine slope failure releases sediments; it is an important mechanism that changes the Earth surface morphology and builds sedimentary records. I study the mechanics of submarine slope failure in sediment that dilates under shear (dilative slope failure). Dilation drops pore pressure and increases the strength of the deposit during slope failure. Dilation should be common in the clean sand and silty sand deposits on the continental shelf, making it an important mechanism in transferring sand and silt into deep sea. Flume experiments show there are two types of dilative slope failure: pure breaching and dual-mode slope failure. Pure breaching is a style of retrogressive subaqueous slope failure characterized by a relatively slow (mm/s) and steady retreat of a near vertical failure front. The retreating rate, or the erosion rate, of breaching is proportional to the coefficient of consolidation of the deposit due to an equilibrium between pore pressure drop from erosion and pore pressure dissipation. The equilibrium creates a steady state pore pressure that is less than hydrostatic and is able to keep the deposit stable during pure breaching. Dual-mode slope failure is a combination of breaching and episodic sliding; during sliding a triangular wedge of sediment falls and causes the failure front to step back at a speed much faster than that from the breaching period. The pore pressure fluctuates periodically in dual-mode slope failure. Pore pressure rises during breaching period, weakens the deposit and leads to sliding when the deposit is unstable. Sliding drops the pore pressure, stabilizes the deposit and resumes breaching. The frequency of sliding is proportional to the coefficient of consolidation of the deposit because dissipation of pore pressure causes sliding. Numerical model results show that more dilation or higher friction angle in the deposit leads to pure breaching while less dilation or lower friction angle leads to dual-mode slope failure. As a consequence, pure breaching is limited to thinner deposits and deposits have higher relative density.

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