All Master's theses from 2001 and PhD dissertations from 2003 to present are found on this page. Dissertation abstracts before 2003 may be found online through Dissertation Abstracts International. The titles in this file have not yet been integrated into the Thesis Subject Index on our web page.
IMAGING THE LOWER SLOPE, OFFSHORE NICARAGUA AND COSTA RICA USING A NEW RESIDUAL MIGRATION VELOCITY ANALYSIS TECHNIQUE IN THE SPACE-OFFSET DOMAIN
by
Imtiaz Ahmed, Ph.D.
The University of Texas at Austin, 2003
Supervisors: Paul L. Stoffa and Kirk D. McIntosh
162 pages, 73 references
There is a dramatic variation in geochemical sediment tracer signal along the Central American volcanic arc. Two contradicting theories, one supporting sediment accretion and the other subduction erosion, have been suggested as possible explanations for these variations. My goal in this dissertation is to use seismic images of the lower slope off Nicaragua and Costa Rica to study the influence of subducting plate structure on sediment dynamics. I am particularly interested in documenting the efficiency of sediment subduction, its along strike variation, and to see if it corresponds with the geochemical anomalies.
Although high quality seismic data was acquired offshore Nicaragua, it remained difficult to image the lower slope in detail with conventional processing techniques. Several characteristics of this geologic environment pose seismic imaging problems: the area is heavily faulted, adjacent reflection boundaries have contrasting dips, and the velocity structure is complex. In this environment the common midpoint gathers do not represent a collection of true common subsurface reflection points. To get a clearer image, I needed to apply pre-stack depth migration (PSDM) techniques. An accurate velocity model is required to get a good PSDM image. Therefore one of the most important aspects of PSDM is velocity analysis. Over the last few decades, residual migration velocity analysis (RMVA) has been an area of active research. Previous work on RMVA in the depth-offset domain required top down layer stripping migration in order to derive the interval velocities directly, hence making it very computationally intensive. Here I propose a new technique in which for each common image gather (CIG) we first create a table of offset-ray parameters-depth ( x-p-z ) using a local 1D assumption. Then I calculate the residual migration depth corrections in the p-z domain and finally map these depth corrections back to the x-z domain using the x-p-z table. Since I calculate the residual migration depth corrections in the p-z domain, the interval velocities are derived directly by top down residual migration. Hence I do not have to explicitly do the layer stripping migration followed by residual normal moveout to get the interval velocities. The velocities generated by using the above RMVA technique produce interpretable depth images of the lower slope off Nicaragua and Costa Rica. From these images I interpret partial sediment accretion off Costa Rica and likely total sediment subduction off Nicaragua, and therefore provide a geophysical evidence for the observed geochemical disparity along this margin.Trevor John Aitken, M.S. GeoSci
The University of Texas at Austin, 2005
Supervisor: Paul Mann
This thesis presents an integrated stratigraphic and tectonic evolution of the Grenada and Tobago basins using multi-channel seismic data collected in May, 2004, (BOLIVAR cruise), along with GULFREX seismic data collected by Gulf Oil Company in 1975. These reflection data, combined with UTIG OBS refraction data also collected with the BOLIVAR study in 2004 and with a compilation of previously published, onland geologic data in the southeastern Caribbean, constrain a multi-stage, Cenozoic tectonic history for the southern Lesser Antilles arc and flanking Grenada and Tobago basins. A new tectonic model for the Grenada and Tobago basins is based on three seismic megasequences. The striking similarity in the two basins’ half-graben structure, smooth basement character, deep-marine seismic facies, and similar Paleogene sediment thickness suggest that the two basins formed as a single, Paleogene forearc basin related to the now dormant Aves Ridge. This single forearc basin continued to open through flexural subsidence during the early to middle Eocene probably because of slow rollback of the subducting Atlantic slab. The Grenada and Tobago basins began to be divided during the early to middle Miocene, when the thinned crust of the forearc was inverted as a result of: 1) oblique convergence between the Caribbean plate and the passive margin of South America; and 2) intrusion of the Neogene Lesser Antilles arc. Observed transpressional shortening of the basins decreases from southwest to northeast. Total shortening in the southern Grenada basin varies from 5 km in the southern part of the study area to 1 km in the northern part of the study area. Shortening structures include inverted Paleogene normal faults, folds, and shale diapirism. The late Miocene to Recent period is characterized by divided depositional histories of the Grenada and Tobago basins. The Tobago basin is characterized by a 4-km-thick wedge of Plio-Pleistocene clastic sediments inferred to represent the distal progradation of the proto-Orinoco River. The Grenada basin becomes increasingly isolated from further continental sediment input by uplift of coastal Venezuelan ranges and the Neogene Lesser Antilles volcanic ridge.
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Supervisors: Stoffa, P. L. and Sen, M. K.
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MULTI-DIMENSIONAL LAND SEISMIC DATA-ACQUISITION TECHNIQUES AND RANDOM SURVEY DESIGN
by Engin Alkan, MS. Geo. Sci.
The University of Texas at Austin , 2007
Supervisor : Bob Hardage
This study analyzes different techniques and innovations of three-dimensional seismic data acquisition and survey design. Multi-dimensional (both 2-D and 3-D) survey design requires objective consideration of survey goals, the range of expected Earth responses, crew and equipment accessibility, acquisition costs, instrument capabilities, experimental field conditions, and logistic considerations.
Planning a 3-D survey combines operational and technical issues which, in turn, depend on acquisition and design parameters. Because seismic source effort, crew and equipment availability, and size and shape of the survey affect survey cost, it is necessary to understand how all of these factors individually affect the overall data-acquisition program. The main goals of this thesis are to analyze the effect of receiving station coordinate randomness on different 3-D seismic data-acquisition and survey design characteristics, both operationally and technically, and to ultimately optimize the cost and data quality of seismic surveys.
Many advances have been made in imaging subsurface structures at both shallow and deep target locations through improved seismic data-acquisition and processing techniques in the past two decades. Service companies and oil companies continue to develop new techniques to create better 3-D images with higher resolution and improved signal-to-noise ratio.
A major problem that confronts onshore seismic exploration companies is the effects of the acquisition geometry on recorded data. Receiver and source line spacings, range of offsets, and azimuths, fold variations, and source-generated noise are all important issues to consider, as are culture, topography, and surface conditions.
This thesis consists of two parts: (1) station randomness effects on acquisition and survey parameters, and (2) experimental evaluation of Vibroseis sweep parameters. To perform the latter analysis, field data acquired across Tohonadla field at Bluff, Utah were processed, and data generated with various Vibroseis sweep parameters were compared. These analyses allowed data-acquisition and survey design parameters to be related to the cost of the survey and to data quality.
MILANKOVITCH ORBITAL FORCING CONTROLS ON SHALLOW-WATER CARBONATE CYCLICITY AND EARLY DOLOMITIZATION: INSIGHTS FROM THE LOWER CRETACEOUS CUPIDO PLATFORM, NE MEXICO
Younis Khamis Altobi, Ph.D
The University of Texas at Austin , 2007
Supervisor: Randall Marrett
High-resolution sequence stratigraphy coupled with understanding of diagenetic processes within carbonate strata improves our understanding of platform evolution controls, facies models, and reservoir quality. The Cupido platform (Barremian to Aptian) exhibits well developed cyclicity and provides unparalleled outcrops to investigate platform morphology, depositional settings, sequence stratigraphic development, origin of high-frequency cycles, and possible climatic controls on early dolomitization across the shelf.
High-frequency cycles stack into twelve depositional sequences (A-L) that correlate across the platform, which, in turn, build into the highstand part of composite sequence I, two complete composite sequences (II and III), and the transgressive based portion of composite sequence IV. Cupido platform interior cycles show evidence for an allocyclic origin, including (a) symmetric and asymmetric peritidal and subtidal cycles, (b) lateral continuity across facies tracts, and (c) incomplete subtidal cycles.
Spectral analyses of cycle thickness reveal a strong Milankovitch signal when sedimentation rate is assumed constant within cycles and cycles are tuned to orbital precession. High spectral density peaks are present for long and short eccentricity (E) period calculated for the Early Cretaceous times: E1 (264-392 kyr), E2 (89-98 kyr), and E3 (107-126 kyr) . Obliquity component with peaks at period (38-59 kyr ) are also present. Strong correlation of Milankovitch signals across the platform suggests that the lateral continuity of high-frequency cycles was caused by shelf-wide sea-level fluctuations.
Early dolomitization of the highstand lower Cupido deposits (LCu) possibly occurred in modified seawater within subtidal and supratidal zones, both at high-frequency cycle-scale and depositional sequence-scale. Dolomitization patterns appear to be linked to Milankovitch-induced 4 th -order sea-level events. The transgressive portions of depositional sequences are more pervasively or preferentially dolomitized compared to the highstand portions. Thickness and periodicity clusters of completely dolomitized cycles are equivalent to thickness and duration of depositional sequences. The results strengthen arguments for the role of Milankovitch-induced sea-level fluctuations in the development of greenhouse carbonate platforms and its control on early dolomite distribution in specific settings.
HIGH-PRESSURE METAMORPHISM IN THE WESTERN LLANO UPLIFT RECORDED BY GARNET-CLINOPYROXENITES IN MASON COUNTY, TEXAS
by
Susan Denise Anderson, M.S.Geo.Sci.
The University of Texas at Austin, 2001
SUPERVISOR: William D. Carlson
Garnet-clinopyroxenites, such as those exposed in Mason County, Texas,
are rare in the Llano Uplift of central Texas and are thus important to interpretation
of the region's metamorphic history. Because our understanding of the metamorphic
history of the Llano Uplift has improved greatly since the garnet-clinopyroxenites
in Mason County were first recognized as high-pressure remnants, a re-evaluation
of their significance has become necessary. This study provides evidence
of in situ metamorphism of the garnet-clinopyroxenites and re-evaluates
previous estimates of pressure-temperature (P-T) conditions during
early metamorphism of the western Llano Uplift. These interpretations place
constraints on tectonic models currently under development for the southern
margin of ancient Laurentia during the Grenville Orogeny.
Mapping of the Purdy Hill locality covered ~2 km2 and revealed for the first time substantial outcrop of retrogressed
garnet-clinopyroxenites within the Lost Creek Gneiss. The mafic bodies
crop out in elongate, pod-like bodies up to 15 m in length and 10 m in width.
The bodies are aligned along two major trends that correlate strongly to
the surrounding structures of the Lost Creek Gneiss. The orientations and
occurrences of the garnet-clinopyroxenites, and the structural setting, of
similar rocks in the eastern Uplift (at smaller scale but better exposed),
lead to the conclusion that these rocks have been boudinaged, indicating
high-grade deformation. These observations provide evidence that the garnet-clinopyroxenites
were metamorphosed in situ, that they and their surrounding rocks
experienced the same metamorphic history.
The retrogressed garnet-clinopyroxenites at the Sterling Jordan locality,
~2 km northwest of the Purdy Hill locality, contain the best-preserved primary
metamorphic assemblage. Fe-Mg exchange thermometry based on interior compositions
of garnet-orthopyroxene pairs and garnet-clinopyroxene pairs yields ~750°C,
which represents peak or near-peak metamorphic temperatures. These temperatures
are supported by the homogenization of garnet growth zoning profiles, the
boudinage seen in the mafic rocks, and anatexis in the surrounding quartzofeldspathic
Lost Creek Gneiss. Pressure estimates are based on the Al content in orthopyroxene
and are complicated by the inhomogeneous distribution of Al within the orthopyroxene
grains, particularly by increases in Al at the orthopyroxene rims toward
grain boundaries. Compositional X-ray mapping of the spatial variation of
Al in orthopyroxene has proven to be an effective method for analyzing such
textural information.
Previous studies estimated peak metamorphic conditions of 8.0 - 11 kbar
at an average temperature of 750°C based on inferred equilibrium between
orthopyroxene rims and garnet interiors (Wilkerson et al., 1988). Re-evaluation
of that study and application of a corrected garnet-orthopyroxene barometer
have led in this study to estimates of 15-21 kbar at 750°C, within the
eclogite facies, based on equilibrium between garnet and orthopyroxene cores,
for the early metamorphism. These new P-T estimates for peak metamorphic
conditions of the western Llano Uplift are significantly different from
estimates for other localities in the north-central and southeastern uplift,
perhaps suggesting important differences in their early metamorphic histories.
Compositional modification of adjacent orthopyroxene and garnet rims,
producing an increase in Al at the margins of orthopyroxene, occurred as
a result of the continued growth of orthopyroxene at the expense of garnet
as the rocks began to re-equilibrate to lower P-T conditions subsequent
to peak metamorphism. The resulting rim compositions of garnet, orthopyroxene,
and clinopyroxene, which likely do not represent complete re-equilibration,
yield 0.3 - 5.4 kbar at an average of 650º C; these conditions represent
the amphibolite facies. Although it is also possible that this partial
re-equilibration occurred along a late, retrograde portion of the same
P- T path that produced peak metamorphism, evidence for hydration during
this recrystallization episode suggests that the partial re-equilibration
was likely associated with the later, lower-pressure amphibolite-facies metamorphism
that occurred across the uplift.
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MODELING OF RUNOFF-PRODUCING RAINFALL HYETOGRAPHS IN TEXAS USING L-MOMENT STATISTICS
By
William Harold Asquith, Ph.D.
The University of Texas at Austin, 2003
Supervisor: John M. Sharp
386 pages, 103 references, 0 plates
Temporal distributions of storm rainfall are known as hyetographs. Design hyetographs are important for cost-effective risk-mitigated ramfall-runoff modeling. The hyetographs considered are known to produce or generate runoff on small watersheds (typically about 50 square kilometers) in Texas. L-moment statistics and the nonparametric median are used to summarize the dimensionless representations of over 1,600 observed hyetograph distributions. A focus is made on storm depths in excess of about 25 mm and durations of 0-12, 12-24, and 24 hours and greater. Statistical distributions are fit to the L-moments of the dimensionless hyetographs including the newly described L-gamma. L-gamma hyetograph models are anticipated to be reliable predictors of expected hyetographs. Finally, a separate permeability-related L-moment application to the popular Carman-Kozeny equation is described.RESERVOIR CHARACTERIZATION OF THE MIOCENE STARFAK AND TIGER SHOAL FIELDS, OFFSHORE LOUISIANA THROUGH INTEGRATION OF SEQUENCE STRATIGRAPHY, 3-D SEISMIC, AND WELL-LOG DATA
by
Adrian Constantin Badescu, Ph.D.
The University of Texas at Austin, 2002
Supervisor: William L. Fisher
METHODS COMPARISONS AND SPATIAL ANALYSIS OF FIELD PARAMETER QUANTIFICATION OF UNSATURATED FLOW AT AN EXISTING WASTEWATER
INFILTRATION SYSTEM; MINES PARK, GOLDEN, COLORADO
by
Danielle Margueritte Bailey, M.S. Geo. Sci.
The University of Texas at Austin , 2006
CO-SUPERVISORS: John E. McCray and Leon E. Long
Subsurface water reclamation systems (SWRS) in mountain watersheds commonly experience issues of water sustainability, and are generally designed through judgment and experience rather than through rigorous quantitative methods. I have made a detailed vadose-zone characterization of several saturated and unsaturated flow parameters in an excavated trench representative of the size of a typical domestic drainage field at a wastewater reclamation test site (WRTS) at Mines Park, Golden, CO with the objective to improve the pre-design techniques associated with SWRS. Most wastewater infiltration is an unsaturated water flow process; therefore, measurement of soil-hydraulic parameters, especially saturated and unsaturated hydraulic conductivity (K sat and K unsat ), is required. Toward this end, I compared the consistency of estimating or measuring K sat and K unsat through field, laboratory, and empirical methods.
Field data collection included Guelph Permeameter and Tension-disc Infiltrometer measurements in the excavated trench, and Slug Test measurements at nearby monitoring wells. Representative soil samples were collected for in-lab experimentation at the UT Bureau of Economic Geology, including the van Genuchten-Mualem transformations of capillary-pressure curves determined from hanging-column measurements. Additional estimates of K sat and K unsat were determined through nine empirical functions and the Rosetta neural network found within Hydrus-1D software. Spatial variations in K sat and K unsat determined from the various methods are illustrated by curves that plot K sat or K unsat according to location. Statistical analyses demonstrate such a large degree of spatial variability that no single measurement adequately represents the values of these parameters, whether along the excavated trench or between the upper and lower tiers of the trench.
The following main conclusions are offered: (1) spatial variations in K sat and K unsat occur along a trench and with depth, in which K unsat exhibits much larger variability with depth than does K sat ; (2) of the empirical functions, results of the Hazen (1893), Harleman et al. (1963), and Beyer (1964) methods compare most favorably to both field methods (Guelph Permeameter, Tension-disc Infiltrometer), providing data that agree with the field-measured values within a factor of two; (3) the Guelph Permeameter field method is the least time consuming and less complicated, but the most arduous to conduct of all field methods; (4) Rosetta estimates with either sand/silt/clay input or soil classification input data provide K unsat values most similar to the Hanging Column values using the van Genuchten-Mualem relationship ; and (5) a single measurement did not appear to represent the hydraulic properties of an entire area occupied by a typical wastewater infiltration trench. I found variation both horizontally along the length of each tier and vertically between Tier 1 (2 feet below ground surface) and Tier 2 (4 feet bgs). This research advances the use of rigorous quantitative measurements and methods in understanding the design of SWRS.
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Osteological Description of an Embryonic Elephant Bird (Ratitae: Aepyornis) Using High-Resolution X-Ray Computed Tomography, With a Discussion of Growth in Aepyornis
by
Amy Michelle Balanoff, M.S. Geo. Sci.
The University of Texas at Austin, 2003
SUPERVISOR: Timothy Rowe
175 pages, 110 references
Very little is known regarding the embryonic skeleton of the extinct elephant bird, Aepyornis, largely due to our hesitation in breaking open rarely recovered intact eggs of this taxon.High-resolution x-ray computed tomography (HRCT), however, provides a non-destructive method for viewing the internal structures of such eggs.The combination of HRCT and three-dimensional rapid prototyping technology made possible the description and reconstruction of a disarticulated embryonic skeleton of Aepyornispreserved within a complete egg.Skeletal elements digitally retrieved from the egg include: the braincase, palate, rostrum, vertebral column, and both fore- and hindlimbs.The cranial morphology of the embryo is well preserved, however due to the early ontogenetic stage of the specimen, development of the postcranial skeleton is less advanced.Comparisons of morphological characters with other embryonic birds allowed an estimation of the ontogenetic maturity as approximately 80-90% through incubation.This specimen, in conjunction with adult material allocated to Aepyornis, was used to construct a growth trajectory that allows a preliminary comparison of growth between Aepyornis and extant ratites.These comparisons offer new insight into the question of how the world’s largest bird got so big.The data suggest that the growth of Aepyornis proceeded in a manner similar to other ratites with a period of rapid growth early in ontogeny that leveled off after hatching.PLIOCENE-QUATERNARY DEFORMATION AND MAGMATISM
AT THE SOUTHERN MARGIN OF THE PUNA PLATEAU, ARGENTINE ANDES
by
Austin Kyle Baldwin, M.S.Geo.Sci.
The University of Texas at Austin, 2005
Supervisor: Randall Marrett
New fault data and mapping of volcanic rocks from northwestern Argentina's Cordillera de San Buenaventura, a Pliocene-Quaternary, E-W trending volcanic range at the southern margin of the Puna plateau adjacent to the modern volcanic arc at 27°S, reveal numerous tectonomagmatic characteristics unique in the region. Faults in the Cordillera de San Buenaventura dominantly strike ENE-WSW, with lengths reaching at least 30-40 km. Fault motion, where measurable, has been normal, commonly with a right-lateral component. Some faults displace alluvium and dated Plio-Quaternary non-explosive lava domes and flows, intermediate in composition, with throws of 1-100 m, whereas other faults do not affect overlying volcanics. Previous studies in the surrounding southern Puna have reported Pliocene-Quaternary NNW-SSE extension along N-S to NNE-SSW striking right-slip faults commonly associated with volumetrically-minor mafic monogenetic cinder cones and flows. Explosive eruptions with intermediate compositions have also characterized the southern Puna during the Pliocene-Quaternary. Volcanics erupted during this time period in the Cordillera de San Buenaventura lack both mafic and explosive tendencies.
The new data, combined with existing data, suggest that the Cordillera de San Buenaventura overlies a shallow magma chamber, which thermally weakened the upper crust and promoted the growth of the observed ENE-WSW striking normal and oblique-slip faults during the Pliocene-Quaternary. The new faults created right-stepping extensional transfers by linking preexisting NNE-SSW striking right-slip faults. Decreased horizontal stress at these transfers facilitated magma ascent from the underlying chamber. Periodic breaches of the magma chamber cupola by slip on faults prevented magmatic fluid accumulation and explosive eruptions. Mafic magma ascending beneath the Cordillera de San Buenaventura pooled in the shallow magma chamber, where it assimilated silica-rich crustal material and differentiated, eventually reaching the surface with an intermediate composition. In surrounding areas, where no shallow magma chamber existed, rising magmas reached the surface with mafic compositions. The high topography of the Cordillera de San Buenaventura may be the combined effect of mechanical doming by the shallow magma chamber, thermal uplift, isostatic elevation of an extensional transfer block, and local accumulation of Plio-Quaternary volcanics.
HYDROTHERMAL FLUIDS AND CU-AU MINERALIZATION OF THE DEEP GRASBERG PORPHYRY DEPOSIT, PAPUA, INDONESIA
Lorraine Marie Baline, M.S. Geo. Sci.
The University of Texas at Austin , 2007
Supervisor: J. Richard Kyle
The Grasberg porphyry Cu-Au deposit is located in the Ertsberg District in the Central Range of Papua, Indonesia. The Deep Grasberg is the deepest explored part of the Grasberg Igneous Complex (GIC) at elevations between 2450 and 3050 m, more than 1100 m below the pre-mining surface. The deposit is hosted by three quartz-monzonite to diorite units, emplaced approximately 3 Ma: the Dalam, the Main Grasberg Intrusion (MGI), and the Kali.
In the Deep Grasberg, the intrusions contain abundant plagioclase phenocrysts with biotite and hornblende as the dominant mafic minerals. Plagioclase has undergone varying degrees of hydrothermal alteration to sericite. Complete alteration of plagioclase to sericite is common in the Dalam, whereas the Early and Late Kali are significantly less altered. Matrix minerals include potassium feldspar and quartz. Quartz occurs as widespread stockwork veins and also is the dominant mineral in the silicified zone, near the GIC-wallrock contact in the Deep Grasberg. Chalcopyrite, with lesser bornite and covellite are the most abundant economic minerals in the Deep Grasberg and are both vein hosted and disseminated. Bornite is most abundant near the center of the Deep Grasberg, whereas covellite abundance increases toward the periphery.
Hydrothermal fluids, supplied from a cupola at depth, created the Grasberg orebody. Due to its relative proximity to the cupola, the Deep Grasberg records a unique fluid evolution and constrains fluid processes during ore formation.
Some changes in the temperature and composition of the hydrothermal fluids in the Deep Grasberg are recorded in quartz crystals. Textures observed using scanned luminescence of 32 samples of quartz veins from the Dalam, MGI, and Kali reveal a complex vein history in the GIC. Alternating light and dark bands forming concentric growth zone textures record changing conditions during quartz precipitation. Point analyses were unable to detect compositional differences in the quartz bands, but X-ray mapping revealed bright bands had higher Al and Ti contents. Subtle compositional changes in quartz suggest that chemical changes in fluid composition may be responsible for the observed growth zonations. Irregular textures in some quartz crystals suggest a period of quartz dissolution occurred as hydrothermal fluids cooled, followed by the resumption of quartz precipitation.
Fluid inclusion populations from 27 samples from the Dalam, MGI, and Kali reveal that a range of fluid compositions were trapped during quartz precipitation. Five types of fluid inclusions are identified: liquid + vapor, vapor-rich, liquid + vapor + halite, liquid + vapor + multi-daughter crystal, and liquid + vapor + opaque. Liquid + vapor + opaque inclusions are believed to represent a supercritical fluid exsolved from a magma at depth, whereas the coexistence of vapor-rich inclusions and high salinity liquid + vapor + halite and liquid + vapor + multi-daughter crystal inclusions represent two separated phases of this fluid after changes in pressure and temperature caused the hydrothermal fluid system to move from the one-phase to the two-phase field. Homogenization temperatures recorded for liquid + vapor + halite, liquid + vapor + multi-daughter crystal, and vapor-rich inclusions are similar. The lowest homogenization temperatures recorded are about 225 °C, but some inclusions did not homogenize at temperatures as high as 700 °C, the maximum temperature able to be reached on the fluid inclusion stage. Two groups emerge from the data, a set of moderate temperature inclusions and a set of higher temperature inclusions. The moderate temperature inclusions have an average homogenization temperature of 368 °C. The higher temperature inclusions have an average homogenization temperature of >598 °C. Calculated salinities for liquid + vapor + halite and liquid + vapor + multi-daughter crystal inclusions indicate that the separated fluid phase from which these inclusions sourced was very saline, containing about 50 wt.% NaCl equivalent. Fluid inclusions in anhydrite from late-stage veins record a significantly cooler fluid, at approximately 250°C at a salinity near 10 wt.% NaCl equivalent.
Similarity in fluid inclusion compositions, temperatures, textures, and chemical zonations in quartz crystals in the veins in all three intrusive units suggest a common fluid source. It also suggests that similar fluid processes were prevalent during quartz vein development in these intrusive units. In the Deep Grasberg, vein quartz precipitated both directly from a supercritical fluid released from a cupola at depth and from a hydrothermal fluid post-boiling. The narrowing of the GIC at depth may have caused “throttling” of fluids in the Deep Grasberg, resulting in relatively increased pressure in the fractures. Decompression of the fluid was inhibited, and fluid inclusions of liquid + vapor + opaque record the earliest fluids . A decrease in pressure resulted in boiling, creating two fluids: a brine and a vapor. These changes in the hydrothermal fluid account for the variety of fluid inclusion types observed in the Deep Grasberg. Additionally, the repetitive growth zonation patterns in quartz suggests that the hydrothermal fluids were released from a cupola at depth into fractures in pulses during quartz precipitation. Fractures remained open, allowing for quartz growth with successive fluid pulses.
THE EFFECTS OF NUTRIENT-BEARING MINERALS ON HYDROCARBON BIODEGRADATION
By
Supervisor: Philip C. Bennett
119 pages, 143 references
Supervisors: James S. Famiglietti, and Clark R. Wilson
After sea surface temperatures, the most important boundary condition for the prediction of climate at the seasonal-to-interannual timeframe is the soil wetness state. Unfortunately, large-scale soil moisture observations are not available, and must therefore be provided through a modeling/data-assimilation approach. Modeling the initial moisture status of a soil requires a comprehensive list of surface water and energy fluxes at consistent temporal and spatial scales. Such data are not presently available except in weather reanalysis products. However, reanalysis products are often biased due to errors in the weather forecast model. In the present study, an attempt to minimize errors to model predictions of the initial soil moisture status is realized through a bias reduction scheme to the reanalysis forcing. The bias reduction scheme uses difference and ratio-based corrections to the reanalysis with global observational datasets. The corrected and original forcing was used to simulate water and energy fluxes within a land surface modeling framework. Output from the land surface model was compared with observations to assess the impact of the bias correction on simulation accuracy. Results of this study demonstrate the implementation of a bias reduction scheme reduces errors in the simulation of runoff, soil moisture, and snow depth. Accordingly, the initializations produced should also be closer to actual surface conditions, and therefore more useful to the climate modeling community. Modelers using reanalysis products for driving land surface models especially for the establishment of initial conditions are cautioned on this approach, and advised to consider a bias reduction strategy.
STRAIN RATES AND CONSTRAINTS ON CHEMICAL HOMOGENEITY AND LENGTH SCALES OF EQUILIBRATION DURING ALPINE METAMORPHISM AT PASSO DEL SOLE, CENTRAL SWISS ALPS
Christopher Andrew Berg, Ph.D.
The University of Texas at Austin , 2007
Supervisor: William Carlson
Garnet-bearing gneisses from the vicinity of Passo del Sole, Central Swiss Alps, have undergone a complex history of metamorphism and deformation that has imbued them with unique compositional and textural variations. Complex, concentric zoning patterns in garnet may be correlated between porphyroblasts on the scale of a hand sample; however, the character of the Ca, Mn, and Y zoning patterns in garnet vary within single layers on the meter-scale. Within a hand sample, individual compositional zones can be correlated from crystal to crystal on the basis of chemical similarities (e.g., intricate yet identical variations in calcium concentration; equivalent manganese concentrations at zone boundaries) and textural similarities (e.g., initiation of inclusion-trail curvature). These relationships allow the identification of individual compositional zones as time markers during garnet growth.
Detailed examination of garnet growth zoning patterns, in combination with measurements of inclusion-trail curvature within garnet porphyroblasts and detailed thermodynamic models of the garnet growth history in selected samples, together with an assumed heating rate associated with Alpine metamorphism, allows quantification of strain-rates during prograde amphibolite-facies metamorphism along the northern margin of the Lucomagno nappe. Constraints on the nucleation and timing of garnet growth and garnet growth rate mechanisms permit further insight into the relationship between strain-rate and metamorphism at Passo del Sole than had previously been possible with this method: variations in strain-rate magnitude of over a factor of ten (10 -14 – 10 -13 s -1 ) are observed, which correlate with core-to-rim changes in compositional zoning.
The source of the incredible diversity of compositional zoning patterns in garnet is hypothesized to be open-system infiltration of ephemeral, channelized Ca- or Mn-rich fluids derived from magmatic sources or equilibrated with metamorphic rocks deeper in the section. Stages of garnet growth associated with increased strain rates are also correlated with the high-Ca or high-Mn zones within the garnet porphyroblasts, presumably as the result of strain softening associated with the passage of these fluids. In-situ oxygen isotope analysis using SIMS demonstrates that the changes in major-element zoning patterns correlate with small shifts in the isotopic composition of garnet.
SEQUENCE STRATIGRAPHY AND DEPOSITIONAL HISTORY OF THE UPPER CAÑON DEL TULE, LAS IMAGENES, AND LOWER CERRO GRANDE FORMATIONS, CENTRAL PARRAS BASIN, NORTHEASTERN MEXICO
by
Juan Clemente Bermúdez Santana, Ph. D.
The University of Texas at Austin, 2003
Supervisor: Richard T. Buffler
210 pages, 100 references, 20 plates
This dissertation describes the results of a field-oriented sequence stratigraphic study of a 900-m-thick Maastrichtian interval in the middle portion of the Upper Cretaceous Difunta Group. Basic analysis of rock features and their stratigraphic arrangement were used to subdivide the interval into transgressive (TST), highstand (HST), and falling stage (FSST) systems tracts and to recognize their bounding surfaces.
The progradational offshore to lower shoreface highstand (HST) deposits of the upper Cañón del Tule Formation and the underlying transgressive (TST) deposits, contain gastropods and bivalves common in shallow marine Lower Maastrichtian strata. However, the occurrence of the ammonite Coahuilites sheltoni restricts these rocks to the lower Upper Maastrichtian.
In the Late Maastrichtian, the final stage of shallow marine sedimentation of the upper Cañón del Tule Formation was characterized by an abrupt change. Accommodation space was reduced in proximal settings, and the shoreline and coarse-grained facies belts migrated basinward in response to a relative sea level fall (forced regression). Wave scouring of the seafloor, and rip and longshore currents produced a regionally extended forced regression surface and sequence boundary characterized by meter-scale gutter casts.
The FSST upper shoreface to foreshore deposits of the uppermost Cañón del Tule Formation include a ridge-forming sandstone of variable thickness. Its internal stratigraphic architecture suggests that high-frequency pulses of sea level risings punctuated the forced regression. During this process, thick, aggradational red deposits of the lower Las Imágenes Formation (FSST) accumulated over the adjacent coastal plain until an intermittent marine transgression began. T he initial transgressive pulses occurred across a rapidly subsiding coastal plain, which favored the development of charophytes in fresh and brackish water environments, associated with benthonic foraminifers, ostracods, oysters, Ophiomorpha and Thalassinoides . Mixed-load probably meandering rivers drained the coastal plain bounded by lagoons and extensive shoreface and offshore environments for this part of the Late Maastrichtian Gulf Coast of México. After this stage of intermittent marine transgression, shallow seas and transgressive (TST) deposits of the lower Cerro Grande Formation covered the region.
STUDIES ON POST-NATAL VARIATION AND VARIABILITY IN THE VERTEBRATE SKELETON AND ITS PALEONTOLOGICAL IMPLICATIONS
Gaberiel Stephen Bever, Ph.D.
The University of Texas at Austin, 2006
Supervisor: Christopher J. Bell
Developmental biology combined with phylogenetic systematics is broadening our perspectives on the role of intraspecific variation in morphology. These perspectives include conceptualizing variability as a reflection of the evolutionary history of the underlying developmental pathways. I conducted a series of studies explicitly addressing the implications that intraspecific variation and variability have for the description, analysis, and interpretation of fossil vertebrates.
The first chapter examines variation in the anuran ilium as a test case for the potential problems that intraspecific variation has on our perceptions of the fossil record. Results indicate that no distinctive morphologies in the ilium of extant North American Bufo are known that support species-level identifications. These observations indicate that our current understanding of the evolutionary history of many extinct and extant taxa based on the fossil record is highly influenced by our assumptions regarding the distribution of taxa through space and time. Restricting identifications to higher taxonomic levels that can be supported with apomorphies helps to avoid circularity if fossil identifications are used subsequently in analyses offaunal dynamics.
Chapters 3 and 4 examine the nature of intrapopulational variation in the crania of two extant turtles, Sternolherus odoratus and Pseudemys texana. Results indicate that the number of variable characters- and the levels at which they vary- are surprisingly high considering the conservative nature of both the taxonomic sample and the pool of examined characters. Variability can be unevenly distributed within and between age groups, sexes, and modular partitions of the skull. Complex patterns of post-natal ossification are a major source of intraspecific variation.
The final chapter examines the potential implications that polymorphic characters have for the phylogenetic assessment of fossils and the potential for objectively estimating variation in extinct lineages. Results indicate that polymorphic characters can significantly affect phylogenetic hypotheses that include fossils. However, a modem view of variability, combined with increasing data on variation in both extant and extinct lineages, not only provides an objective means to estimate variation in fossil specimens but represents a largely untapped source of phylogenetic information that is a potentially important research trajectory in evolutionary morphology.
THE ORIGIN AND EVOLUTION OF THE GRAN DESIERTO SAND SEA
By
Carrie Ann Beveridge
University of Texas at Austin, 2004.
Supervisor: Kocurek, Gary
TIDAL SIGNATURES IN SAND PRONE, TECTONICALLY GENERATED JURASSIC STRAITS, SCOTLAND
Stuart Blackwood, MSGeoSci
The University of Texas at Austin , 2006
Supervisor: Ron J. Steel
The Mid-Jurassic Bearreraig Formation is superbly well exposed on the Isles of Skye and Raasay in NW Scotland. In southern Skye the Bearreraig displays a spectacular, cyclical hierarchy of sand rich, tide-generated bedforms:
1. Upward thickening to thinning compound and compound-compound trough cross-sets (3D dunes) up to 2.5m thick
2. Compound trough cross-sets (3D dunes) up to 10m thick
3. Upward thinning, simple and compound planer cross-sets (2D dunes) up to 50cm thick
Tectonically-generated sequences (up to 140m thick) consisting of these three dune types can be recognized within the formation.
Sedimentation occurred in NNE-SSW-aligned, North Skye/Raasay and South Skye half-grabens, defined by Aalenian-Bajocian faulting associated with the initial opening of the North Atlantic . SSW oriented (S. Skye) and NNE oriented (N. Skye/Raasay) fault-parallel paleocurrent directions (indicative of basin separation) suggest that the faults were active and had enough topographic expression to enhance the tidal regime in these very narrow, block-tilted zones.
Previous depositional interpretation of the Bearreraig is one of alternating tide-dominated deltaic and macro-tidal estuarine cycles with high-frequency regressions and transgressions. Facies cropping out at Trotternish in N. Skye, and Raasay display trends consistent with this regional interpretation. However, in southern Skye the overall thickness of the cross-stratified succession, anomalously large size of the bedforms (implying relatively deep water), intensely sand-rich character of the succession, together with the high bioclastic content of broken shell debris is indicative of a more complex, higher-energy depositional environment. The character and scale of the bedforms, and the absence of pro-delta, lagoonal or delta-plain deposits suggests a narrow seaway or tidal strait generated by active tilting of narrow fault blocks.
FIELD EXPERIMENTS FOR FRACTURE CHARACTERIZATION: STUDIES OF SEISMIC ANISOTROPY AND TRACER IMAGING WITH GPR
Nedra Danielle Bonal, Ph.D.
The University of Texas at Austin , 2007
Supervisor: Clark R. Wilson
Knowledge of fracture orientation and density is significant for reservoir and aquifer characterization. In this study, field experiments are designed to estimate fracture parameters in situ from seismic and GPR (radar) data. The seismic experiment estimates parameters of orientation, density, and filling material. The GPR experiment estimates channel flow geometry and aperture.
In the seismic study, lines of 2D data are acquired in a vertically fractured limestone at three different azimuths to look for differences in seismic velocities. A sledgehammer, vertical source and a multicomponent, Vibroseis source are used with multicomponent receivers. Acquisition parameters of frequency, receiver spacing and source-to-receiver offset are varied. The entire suite of seismic body waves and Rayleigh waves is analyzed to characterize the subsurface. Alford rotations are used to determine fracture orientation and demonstrate good results when geophone orientation is taken into account. Results indicate that seismic anisotropy is caused by regional faulting. Aaverage fracture density of less than 5% and water table depth estimates are consistent with field observations. Groundwater flow direction has been observed by others to cross the fault trend and is subparallel to a secondary fracture set. In this study, seismic anisotropy appears unrelated to this secondary fracture set. Vp/Vs and Poisson's ratio values indicate a dolomite lithology. Sledgehammer and Vibroseis data provide consistent results.
In the GPR experiment, reflection profiles are acquired through common-offset profiling perpendicular to the dominant flow direction. High frequency waves are used to delineate fluid flow paths through a subhorizontal fracture and observe tracer channeling. Channeling of flow is expected to control solute transport. Changes in radar signal are quantitatively associated with changes in fracture filling material from an innovative method using correlation coefficients. Mapping these changes throughout the survey area reveals the geometry of the flow path of each injected liquid. The tracer is found to be concentrated in the center of the survey area where fracture apertures are large. This demonstrates that spatial variations in concentration are controlled by fluid channel geometry.
Supervisor: Famiglietti, J. S.
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RECHARGE IN A SEMI-ARID BASIN AQUIFER: RYAN FLAT AND LOBO FLAT,
TRANS-PECOS, TEXAS
by
Norman G. Van Broekhoven, M.S. Geo. Sci.
The University of Texas at Austin, 2001
Supervisor: John M. Sharp
Field mapping of fractures in mountain canyons, analysis of digital elevation models and aerial photographs indicate that the position of the mountain canyons and streams are controlled by fractures. The mechanisms of recharge seem to be a combination of fracture infiltration and flow in the mountains, infiltration into the bottoms of ephemeral streams in mountain canyons that are located along fracture zones, and infiltration of ephemeral streams near the basin margin. Digital elevation models (DEMs) were proven to be useful for identifying topographic linears caused by fractures in the mountains and under the basin fill. DEMs were able to enhance topographic trends that were less evident in aerial photographs having a much higher resolution.
ESTIMATING BIOZONE HYDRAULIC CONDUCTIVITY IN WASTEWATER SOIL ABSORPTION SYSTEMS USING INVERSE NUMERICAL MODELING
by
Johnathan R. Bumgarner, M.S. Geo. Sci.
The University of Texas at Austin, 2005
SUPERVISORS: John E. McCray and Bridget R. Scanlon
Wastewater soil absorption systems (WSAS) are commonly used in the United States to treat domestic wastewater prior. Soil clogging occurs at the infiltrative surface of WSAS due to the accumulation of suspended solids, organic matter, and chemical precipitates during continued wastewater infiltration. This low permeability zone is referred to as a biozone. A certain degree of clogging enhances wastewater treatment due to increased residence times and nutrient use by organisms. Conversely, too much clogging can cause WSAS to backup and ultimately fail. As such, determining a generalized set of biozone hydraulic parameters and whether those parameters vary in different types of WSAS or for different loading rates are integral to proper WSAS design and installation.
Because the system is unsaturated and the biozone-soil interface behaves like a capillary barrier, simply estimating infiltration using Darcy’s equation, which assumes saturation, may not be appropriate. Therefore, inverse modeling was conducted using the HYDRUS-1D multi-phase modeling software. Input data for the model simulations, which include infiltration rates and soil hydraulic parameters, were determined at a test site at Colorado School of Mines (CSM). The test site includes ten each of three different types of WSAS – bundle, chamber, and gravel – for a total of 30 test cells. Half of the test cells received a loading rate of 4 cm/day, while the other half received 8 cm/day for one year. Both of these loading rates are higher than the Jefferson County, CO, recommended loading rate of 2 cm/day. Use of different loading rates is an attempt to simulate systems of different ages because the biozone becomes less permeable as the WSAS ages. Constant head infiltration tests were conducted by researchers at CSM in each of the test cells at the time of site installation to calculate the saturated hydraulic conductivity (K s) of the soil, and falling head infiltration tests were conducted after 12 months to calculate the biozone K s.
HYDRUS-1D was used to establish the retention function parameters and K s for biozones at Mines Park via inverse modeling. Of the parameters estimated by HYDRUS-1D inverse simulations, K s has the greatest impact on the falling head test model results when the system is near saturation (volumetric water content > 90%). According to the simulation results, the biozone is near saturation and, therefore, K s weighted most heavily in the data analysis. Results of the modeling process indicate that there are no significant differences (α=0.10) between the mean K s of cells of different types or loading rates (total mean K s = 2.12 cm/day ± 0.78). On the other hand, there is a significant difference (α=0.10) between the mean K s calculated by HYDRUS-1D (2.12 cm/day ± 0.78) and that calculated by Darcy’s equation (3.02 cm/day ± 0.89), but that difference is physically inconsequential. Ponding did not occur in any of the WSAS simulations with 2 cm/day loading rates. Finally, an acceptable set of biozone hydraulic parameters for each of the test cells is established by the modeling process for use at the CSM outdoor laboratory. These parameters will be used to constrain transport in future investigations at the site including contaminant attenuation and loading rate studies.
MID-PLEISTOCENE TO PRESENT STRATIGRAPHIC RESPONSES IN A TECTONICALLY- D RIVEN DEPOSITIONAL SETTING: EEL RIVER BASIN, NORTHERN CALIFORNIA
by
Robert Lawrence Burger, Ph.D.
The University of Texas at Austin, 2002
Supervisors: William E. Galloway, Craig S. Fulthorpe, James A. Austin, Jr.
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A GENERAL TRANSFORM FOR REVERSIBLE SEISMIC DATA PROCESSING BY NONSTATIONARY FILTERING
William Andrew Burnett, M.S. Geo. Sci.
The University of Texas at Austin , 2007
Supervisor: Robert J. Ferguson
I use the nonstationary equivalent of the Fourier shift theorem to derive a general one-dimensional integral transform for the application and removal of certain seismic data processing steps. This derivation comes from the observation that many seismic data processing steps can be viewed as nonstationary shifts themselves. The nonstationary frequency and time distortions inherent to many seismic data processes are predicted and quantified by this transform. Once the transform is developed, I demonstrate matrix-vector multiplication as a valuable tool for implementation. I use the normal moveout (NMO) correction and Stolt migration as examples. Displaying the integration kernel matrices yields insight to the mechanics of their respective transforms, and also reveals symmetries that can be exploited to improve computational efficiency. Matrix-vector multiplication is an intensely studied field in applied mathematics and computer science, so there are many algorithms available to further increase efficiency. Most of these algorithms offer a trade-off between accuracy and efficiency, and some even offer to quantify the error associated with their approximation. Unlike conventional processing algorithms that require interpolation, data processing steps performed by matrix vector multiplication are reversible within computational accuracy. I show that interpolation schemes are a frequency band-limited approximation to the transform method I develop. Just as the Fourier inversion theorem justifies the Fourier domain as a valid processing domain, the reversible data processing transform quantitatively justifies using processed data as if it is in a new domain.
TEMPORAL AND SPATIAL SULFATE VARIABILITY IN GROUNDWATER AT A LIGNITE MINE, NORTHEAST TEXAS
Margaret Frances Cagle, M.S. Geo. Sci.
The University of Texas at Austin, 2007
Supervisor: John M. Sharp
Sulfate (SO 4 2- ) concentrations in the groundwater at the Luminant Monticello lignite mine, northeast Texas, vary with both time and space. SO 4 2- is monitored closely because it is a product of chemical reactions that can lead to acid mine drainage. Although acid mine drainage is not a problem at Monticello, SO 4 2- concentrations in some areas are high and correspond to high total dissolved solids (TDS), low pH groundwater. At Monticello, chloride, total dissolved iron, and total dissolved manganese concentrations also are variable. To examine this variability, 46 monitoring wells are divided into those: 1) screened in rock underneath the lignite seam (underburden); 2) screened in the rock over the lignite seam (overburden); and 3) screened in the reclaimed spoil. There is a wide range of SO 4 2- concentration across the mine with statistically significant differences between the SO 4 2- distributions for each well category. Three hypotheses may explain the spatial SO 4 2- variability: (1) The heterogeneity of the mined material (2) Flushing of SO 4 2- from the reclaimed section into the overburden (3) Exposing iron sulfides to oxidizing conditions when the water table is dropped by mine dewatering operations. Possible sources of SO 4 2- include the oxidation of pyrite and/or the dissolution of gypsum.
Temporal SO 4 2- variability is evident in the SO 4 2- time series for each well. In the underburden, SO 4 2- seems to be approaching a steady state; however, some wells in the unmined overburden and reclaimed area have SO 4 2- trends that are increasing or are highly variable with time. Water table fluctuations or flushing caused by seasonal meteorological changes may control these trends.
Correlation analyses show that for most underburden, overburden, and reclaim wells, SO 4 2- does not correlate with pH, indicating that acidity does not accompany the incorporation of SO 4 2- and that SO 4 2- may be advected from another part of the mine. Analysis of water level and SO 4 2- time series, as well as Cl - and SO 4 2- time series, show that advection from reclaimed areas cannot account for every high SO 4 2- value or increasing SO 4 2- concentration in the overburden and reclaim. Groundwater in most overburden and reclaimed areas are at equilibrium with gypsum, indicating gypsum precipitation if SO 4 2- is flushed into the area and gypsum dissolution if SO 4 2- is flushed out.
Time series analyses shows some of the wells with increasing SO 4 2- concentration to be approaching equilibrium. Also, most SO 4 2- time series have a seasonal component. Flushing from the reclaimed areas is considered to be the dominant process controlling SO 4 2- variability in the overburden. A combination of flushing and aqueous geochemical processes related to heterogeneity controls the SO 4 2- concentration in the reclaimed land.
DEVELOPMENT OF THE LOS CHIVOS PLATFORM, A PALEOCENE CARBONATE BUILDUP IN A SILICICLASTIC DOMINATED SALT BASIN, LA POPA BASIN, NORTHEAST MEXICO
by
Mathew Allan Campbell, MS Geo Sci
The University of Texas at Austin, 2003
Supervisor:William L. Fisher for R. K. Goldhammer (Deceased)
118 pages, 31 references, 4 plates
Integrating Seismic Geomorphology into improved reservoir models of Shelf Margin Deltas, Corallita/Lantana Field, Trinidad
by Terence Campbell, MS. GeoSci
The University of Texas at Austin , 2006
Supervisor : Lesli Wood
This project analyzes the reservoir architecture and compartmentalization of the as yet undeveloped Corallita and Lantana gas fields. Corallita-Lantana, discovered by Amoco Production Company in 1995, is an undeveloped dry gas discovery in the Greater Mahogany region offshore in the eastern shelf of the Columbus Basin , offshore S.E. Trinidad (Wood, 2004). It is currently estimated to contain 1.5 TCF of gas resource in Pleistocene age reservoirs.
Several factors complicate development of the Corallita-Lantana field, including fault seal, trap definition and reservoir compartmentalization. 1120 km 2 of 3D seismic combined with well log analysis have been used to explain the reservoir shape, size and distribution. Seismic coherency, amplitude analysis and spectral decomposition have been integrated to improve understanding of reservoir heterogeneity and compartmentalization, and spatial changes in reservoir petrophysics. Such knowledge will enable engineers to establish the best production design, and implement the most economical artificial drive mechanism for production.
I made statistically robust, geomophometric analysis of the reservoir by assigning binary codes to various facies and incorporating well log character using cumulate analysis software on interactive computer workstations. The reservoir of interest (TQ60) shows varying seismic facies architecture from shelf to slope. The seven seismic facies identified are conformable topset facies, interchannel facies, canyon facies (mass transport deposits), channel levee systems, ponded turbidities, conformable horizontal slope facies and faults which are identified on seismic attributes extractions. Assigning digitized codes to different facies is a fast and effective way to model a reservoir and compare different data sets.
The result of combining geomorphology from seismic attributes to reexamine the stratigraphic framework is a predictive tool that strengthens any model from sediment content, basin plays characterization, risking prospects and well placement models. Development of the field is now being planned and approximately 56% of the reserves are in the Pleistocene age TQ60 sand across both the Lantana and Corallita fault segments. Results from this study do not only apply to the development of the field, but explain how reservoir shape and distribution can be addressed in all shallow marine and fluvial-deltaic environments.
SEISMICITY AND TECTONICS OF THE ARC SEGMENTATION IN THE SOLOMON ISLAND ARC, SW PACIFIC OCEAN AND THEIR RELATION TO SUBDUCTING BATHYMETRIC FEATURES
by
Ming-Chu Chen, M.S.Geo.Sci.
The University of Texas at Austin , 2007
SUPERVISORS: Cliff Frohlich and Fred W. Taylor
For the Solomon Island arc we evaluate arc segmentation as defined by seismological and geological evidence. Seismological evidence that defines arc segment boundaries includes seismicity patterns, aftershock areas for large earthquakes, focal mechanisms, and variations in seismic moment release; the geologic evidence is mostly information about Holocene vertical movements, drowned coastlines and especially uplifted coral reef terraces, sometimes augmented by dated coral samples. We identify three major tectonic regimes or supersegments that correspond respectively to the areas surrounding Bougainville, New Georgia, and Guadalcanal-San Cristobal Islands . We speculate that subduction of the young Woodlark spreading center is what distinguishes the central New Georgia supersegment from the two neighboring supersegments. The New Georgia supersegment has relatively higher uplift rates, smaller arc segments, and more small islands; prior to the 1 April 2007 M B w B 8.1 earthquake it had generally lower rates of seismic activity than the neighboring supersegments. Altogether we identify twenty two segment boundaries, including eleven major segment boundaries, four minor boundaries, and seven possible boundaries in the Solomon Islands . Generally the mean along-arc lateral extent of Solomons arc segments are smaller than segments reported in other island arcs; this may be real but it may occur simply because the high seismicity rates and coral-friendly tropical environment provide an unusually favorable situation for observing variations in vertical tectonic activity and thus segment boundaries.
STRUCTURAL ANALYSIS OF CENOZOIC FAULT SYSTEMS USING 3D SEISMIC DATA IN THE SOUTHERN MARACAIBO BASIN, VENEZUELA
By
Maria Veronica Castillo, PhD.
University of Texas at Austin, 2001.
Supervisor: Fisher, W. L.
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THREE-DIMENSIONAL STRATAL DEVELOPMENT OF A CARBONATE-SILICICLASTIC SEDIMENTARY REGIME, NORTHERN CARNARVON BASIN, NORTHWEST AUSTRALIA
by
Donna Louise Cathro, Ph.D.
The University of Texas at Austin, 2002
Supervisors: William L. Fisher and James A. Austin, Jr.
TIME-LAPSE (4-D), VP/VS INTERPRETATION
OF RESERVOIR DEPLETION IN TEAL SOUTH FIELD, GULF OF MEXICO
by
Fernando Antonio Cerda, M. S. Geo Sci.
The University of Texas at Austin, 2001
EVOLUTION OF THE TOBAGO FOREARC BASIN: IMPLICATIONS FOR SEDIMENTATION AND HYDROCARBON PRODUCTIVITY
by
Nysha Alana Niela Chaderton,
The University of Texas at Austin, 2005
Supervisor: Lesli Wood
The relationship of the Lesser Antilles Island Arc, the Tobago Forearc Basin and the Barbados Accretionary Prism shows classic convergent margin/subduction zone geometry. The island of Barbados is the only emergent part of the accretionary prism, with 80% of the land area being covered by Pleistocene limestone which has been eroded in the NE to expose the older rocks of the accretionary prism. A 450 km 2 2D seismic data volume allows for the extension of these stratigraphic units offshore and allows for the definition of a structural framework for the region. The relationship between the unit identified onshore as the Early Eocene to Middle Miocene Oceanic Formation and the basal unit, the intensively folded and faulted Eocene Scotland Formation, has long been cause for debate. It has been previously proposed that the Oceanic Formation, which consists of pelagic clays with some ash beds, is allocthonous and has been thrusted into its present position, overlying the accreted sediments of the Scotland Formation. However the seismic data shows no evidence of the nappes which are the basis for this theory. The opposing theory is that the Oceanic Formation is related to the 12 km of sediment which fills the Tobago Forearc Basin and has been deposited in situ. This is supported by the relationships between the seismic facies which shows the onlap of the Oceanic Formation onto the older accreted sediments.
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THE RELATIONSHIP OF MAMMALIAN MORPHOMETRIC DIVERSITY
TO ENVIRONMENTAL VARIATIONS AND ITS USE IN PALEOCLIMATIC RECONSTRUCTIONS
by
John Lee Chaille, PhD
University of Texas at Austin, 2001.
Supervisors: Lundelius, E. L. and Rowe, T. B.
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AN INTEGRATED GEOLOGIC MODEL OF VALHALL OIL FIELD FOR NUMERICAL SIMULATION OF FLUID FLOW AND SEISMIC RESPONSE
Samarjit Chakraborty, MS
The University of Texas at Austin, 2007
Supervisor: Dr. Robert Ferguson
Time-lapse seismic monitoring promises to be a valuable tool for reservoir engineering as it provides dynamic data over the entire ?eld rather than the spatially limited production data. In this thesis, I develop a link between computerized reservoir simulation, rock physics, and seismic analysis. I present an example study of time-lapse seismic e ? ects in a sequence of reservoir simulation, rock physics, and seismic forward modeling. The thesis includes a case-study of the Valhall ?eld which I propose be used for an integrated geologic model for ?uid ?ow and seismic simulation.
I combine ?uid ?ow simulation studies with a parallel ?ow simulation code IPARS to obtain computed pore pressure and oil saturation at di ? erent spatial location as a function of time. The reservoir model for ?uid ?ow simulation input is linear and isotropic. The reservoir model has an injection well below the oil-water contact and a producer well at a shallower level. The variations of pore pressure due to injection and production cause 3-D multi-phase ?uid ?ow in the reservoir with time.
I develop a rock physics mapping code to estimate the P-wave and S-wave seismic velocities and densities for seismic forward modeling from pore pressure and water and oil saturation obtained by ?uid ?ow simulation. The rock physics code uses Gassmann's relations for ?uid substitution to compute the seismic re?ection parameters.
Migrated depth sections show brightening of amplitude values near the producer well as a function of time. Re?ections from the production zone appear stronger indicating high oil saturation values with increasing production.
I develop a case-study of the Valhall Field to make an integrated geologic model for ?uid ?ow and seismic simulation. Based on an initial description of reservoir geology, I combine rock-physics measurements, ?uid properties, geomechanics, seismic, well, and checkshot data, to build an integrated model for simulations of subsurface ?uid-?ow and surface seismic data.
STRUCTURAL GEOLOGY OF THE PACHECO PASS AREA, DIABLO RANGE, CALIFORNIA: EXHUMATION OF A COHERENT BLUESCHIST TERRANE IN THE FRANCISCAN SUBDUCTION COMPLEX
by
Kirk Chatawanich, M.S. Geo. Sci.
The University of Texas at Austin, 2001
Supervisor: Mark Cloos
The world's largest terrane of coherently bedded blueschist-facies metamorphic rocks containing jadeitic pyroxene plus quartz is exposed in the Franciscan Complex core of the Diablo Range of Central California. Petrologic studies by W .G. Ernst and others have shown that peak metamorphic temperatures were in the range 150-250ºC and pressures were 7-8 kbar. Plate convergence explains how these sediments were subducted to depths of 25-30 km, but the exhumation of these rocks and juxtaposition against upturned strata of the Great Valley Group is problematical.
In the Diablo Range, Franciscan rocks deposited during the Late Jurassic Cretaceous are found in contact with Great Valley Group sedimentary rocks of roughly the same age across the high-angle Ortigalita Fault. North of San Francisco, the Great Valley strata are separated from the Franciscan by the sheared ultramafic and mafic igneous rocks of the Jurassic Coast Range Ophiolite. Isotopic age data indicate peak temperatures were attained around 100 Ma, and fission track thermochronology indicates a major period of cooling occurred at 100-70 Ma. Franciscan detritis began to appear in the geologic record in the Eocene at about 50 Ma. Volcanic rocks dated it 9-11 Ma are deposited on Franciscan rocks in the Diablo Range, indicating uplift and exhumation to surface levels had occurred by that time.
Near Pacheco Pass, California, Franciscan strata are exposed along a 4 km transect cut by California Highway 152 and a 3.1 km transect cut by the old road through the pass. Structural analysis along 4.3 km of total roadcut exposures was performed in order to determine average orientations of structures along the traverse. The Franciscan strata consist mainly of interlayered greywacke and shale with subsidiary beds of chert and rare conglomerate lenses. Paleotop indicators were found at only nine localities, and all but one indicate the nearby section is upright. In many roadcuts, individual beds can be traced for tens of meters. There is no evidence of a greenschist facies overprint, and the presence of aragonite veins indicates that exhumation to depths less than 10 km occurred under cool, syn-subduction geothermal conditions.
Franciscan strata exposed along the transacts contain numerous angular folds and quartz veins. Planar faults with thin cataclastic zones are common. The attitudes of 1280 bedding surfaces, 2297 metamorphic foliations, 1073 fold hinge lines, 4036 veins, and 109 faults were measured along the roadcuts. Metamorphic foliations are bedding-parallel and folded. Upright chevron folds with moderately to steeply dipping limbs are common in the central part of the field area along Highway 152 and near the Ortigalita Fault. Some veins are bedding/foliation parallel, but most are perpendicular to foliations and indicate NE-SW extension direction, roughly perpendicular to the Ortigalita Fault. Most fold axes have an average NE-SW trend. The bedding-parallel cleavage indicates bedding-perpendicular shortening, whereas many veins and normal faults indicate roughly NE-SW extension.
The structural geology of the jadeitic rocks near Pacheco Pass can be explained with a history in which strata deposited on the Farallon plate during the Mesozoic were subducted to depths of 20-30 km. Stratal coherency at the scale of tens of meters was largely maintained during subduction, deep accretion by underplating, uplift and exhumation. The folding of bedding-parallel cleavage, most veining, and faulting post-date peak temperatures. The metamorphic foliation., veins, normal faults, and folds are most simply explained as forming during a near-vertical syn-subduction exhumation driven by deeper-seated underplating. Over tens of m.y., this process drove deeply accreted sediments through the crystalline base of the overriding North American plate to form the Diablo Range anticlinorium in the forearc basin setting.
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SEISMICITY AND TECTONICS OF THE ARC SEGMENTATION IN THE SOLOMON ISLAND ARC, SW PACIFIC OCEAN AND THEIR RELATION TO SUBDUCTING BATHYMETRIC FEATURES
by
Ming-Chu Chen, M.S.Geo.Sci.
The University of Texas at Austin , 2007
SUPERVISORS: Cliff Frohlich and Fred W. Taylor
For the Solomon Island arc we evaluate arc segmentation as defined by seismological and geological evidence. Seismological evidence that defines arc segment boundaries includes seismicity patterns, aftershock areas for large earthquakes, focal mechanisms, and variations in seismic moment release; the geologic evidence is mostly information about Holocene vertical movements, drowned coastlines and especially uplifted coral reef terraces, sometimes augmented by dated coral samples. We identify three major tectonic regimes or supersegments that correspond respectively to the areas surrounding Bougainville, New Georgia, and Guadalcanal-San Cristobal Islands . We speculate that subduction of the young Woodlark spreading center is what distinguishes the central New Georgia supersegment from the two neighboring supersegments. The New Georgia supersegment has relatively higher uplift rates, smaller arc segments, and more small islands; prior to the 1 April 2007 M B w B 8.1 earthquake it had generally lower rates of seismic activity than the neighboring supersegments. Altogether we identify twenty two segment boundaries, including eleven major segment boundaries, four minor boundaries, and seven possible boundaries in the Solomon Islands . Generally the mean along-arc lateral extent of Solomons arc segments are smaller than segments reported in other island arcs; this may be real but it may occur simply because the high seismicity rates and coral-friendly tropical environment provide an unusually favorable situation for observing variations in vertical tectonic activity and thus segment boundaries.
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MICROFACIES AND DEPOSITIONAL ENVIRONMENTS OF SELECTED PENNSYLVANIAN CALCAREOUS ALGAL DEPOSITS FROM SOUTHERN U.S.A., AND APPLICATION OF INFORMATION TECHNOLOGY FOR SEDIMENTARY PETROLOGY TEACHING AND RESEARCH
by
Suk-Joo Stephen Choh, Ph.D.
The University of Texas at Austin, 2004
Supervisor: William L. Fisher
168 pages, 209 references
Another method of building a digital petrography image archive was devised to supplement the labor-intensive nature of teaching optical petrography. The architecture, process, and lessons learned from developing an interactive multimedia CD-ROM tutorial in sandstone petrology for undergraduates is documented. This approach provides possible models for similar development in other fields of petrography or in any other field that utilizes large quantities of visual material, such as seismic or remote-sensing image interpretation.
SILICATE SURFACE CHEMISTRY AND DISSOLUTION
KINETICS IN DILUTE AQUEOUS SYSTEMS
by
Wan-Joo Choi, Ph.D.
The University of Texas at Austin, 2004
Supervisor: Philip C. Bennett
268 pages, 116 references
Lower activation energies in organic ligand solutions suggest that: (1) the metal-organic complex is more stable at lower temperatures; or (2) the dominant reaction mechanism at a high temperature region may be proton-promoted and is ligand-promoted at a lower temperature region.
DEPOSITIONAL AND STRUCTURAL EVOLUTION OF THE MIDDLE MIOCENE DEPOSITIONAL EPISODE, EAST-CENTRAL GULF OF MEXICO
by
Ricardo Ignacio Combellas Bigott, Ph.D.
The University of Texas at Austin, 2003
Supervisor: William E. Galloway
291 pages, 137 references, 38 plates
A large volume of sediment bypassed the confined minibasin province and the unconfined Florida slope at the flank of active deltaic depocenters, forming the long-lived MCAVLU submarine fan system (named for its location beneath the Mississippi Canyon, Atwater Valley, and Lund continental shelf (OCS areas) in the linked, primary minibasin corridor of the lower slope and basin floor. The MCAVLU submarine fan system evolved from a structurally-controlled, elongate sand-rich to mixed sand/mud fan to a large radial, mixed sand/mud fan. Significant untapped middle Miocene hydrocarbon resources remain in the confined channel fills and lobes of the Harang collapse system and sand-rich ponded facies assemblages of the MCAVLU submarine fan system.
SPATIAL DELINEATION, FLUID-LITHOLOGY CHARACTERIZATION, AND PETROPHYSICAL MODELING OF DEEPWATER GULF OF MEXICO RESERVOIRS THROUGH JOINT AVA DETERMINISTIC AND STOCHASTIC INVERSION OF 3D PARTIALLY-STACKED SEISMIC AMPLITUDE DATA AND WELL LOGS
Arturo Javier Contreras, Ph.D.
The University of Texas at Austin , 2006
Supervisor: William L. Fisher & Carlos Torres-Verdin
This dissertation describes a novel Amplitude-versus-Angle (AVA) inversion methodology to quantitatively integrate pre-stack seismic data, well logs, geologic data, and geostatistical information. Deterministic and stochastic inversion algorithms are used to characterize flow units of deepwater reservoirs located in the central Gulf of Mexico. A detailed fluid/lithology sensitivity analysis was conducted to assess the nature of AVA effects in the study area. Standard AVA analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generate typical Class III AVA responses. Layer-dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution, indicating that presence of light saturating fluids clearly affects the elastic response of sands. Accordingly, AVA deterministic and stochastic inversions, which combine the advantages of AVA analysis with those of inversion, have provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties and fluid-sensitive modulus attributes (P-Impedance, S-Impedance, density, and LambdaRho, in the case of deterministic inversion; and P-velocity, S-velocity, density, and lithotype (sand-shale) distributions, in the case of stochastic inversion).
The quantitative use of rock/fluid information through AVA seismic data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, provides accurate 3D models of petrophysical properties such as porosity, permeability, and water saturation. Pre-stack stochastic inversion provides more realistic and higher-resolution results than those obtained from analogous deterministic techniques. Furthermore, 3D petrophysical models can be more accurately co-simulated from AVA stochastic inversion results. By combining AVA sensitivity analysis techniques with pre-stack stochastic inversion, geologic data, and awareness of inversion pitfalls, it is possible to substantially reduce the risk in exploration and development of conventional and non-conventional reservoirs.
From the final integration of deterministic and stochastic inversion results with depositional models and analogous examples, the M-series
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