Previamente à cada estimativa ou simulação geoestatística os domínios geológicos do depósito devem ser modelados, o que tradicionalmente é feito de forma manual por um geomodelador, em um processo laborioso, demorado e subjetivo. Por essa razão novas técnicas conhecidas como métodos implícitos veem surgindo. Essas técnicas fornecem algoritmos que substituem o processo de digitalização manual dos métodos explícitos por alguma forma de procedimento automático. Essa dissertação visita alguns métodos implícitos bem estabelecidos com atenção especial à modelagem geológica implícita com funções distância assinalada. Um estudo de caso em um banco de dados real é apresentado e a aplicabilidade do método discutida. Embora não substitua por completo um geomodelador experiente, o método provou ser capaz de gerar modelos geológicos semi-automáticos realistas a partir dos dados amostrais, e se mostra útil principalmente nas fases iniciais da pesquisa mineral. / Prior to every geostatistical estimation or simulation study there is a need for delimiting the geologic domains of the deposit, which is traditionally done manually by a geomodeler in a laborious, time consuming and subjective process. For this reason, novel techniques referred to as implicit modelling have appeared. These techniques provide algorithms that replace the manual digitization process of the traditional methods by some form of automatic procedure. This dissertation covers a few well established implicit methods currently available with special attention to the signed distance function methodology. A case study based on a real dataset was performed and its applicability discussed. Although it did not replace an experienced geomodeler, the method proved to be capable in creating semi-automatic geological models from the sampling data, especially in the early stages of exploration.

The Pliocene, a geologic epoch spanning ~2.6-5.3 million years ago (Ma), was a period in Earth’s history where temperatures were several degrees warmer than today and atmospheric CO2 was close to modern levels, making it an analogue for future climate change. Following this interval, the planet’s climate shifted to the familiar glacial-interglacial cycles of the Pleistocene (~0-2.6 Ma), beginning with the development of extensive Northern Hemisphere ice sheets at ~2.7 Ma. In response to these changes through the Plio-Pleistocene, several components of the Earth System, particularly related to East Asia and the North Pacific Ocean, varied both temporally and spatially, further modifying regional and global climate through various feedbacks. In this thesis, I utilize a combination of geochemical proxies derived from North Pacific marine sediments as well as a regional climate model to better understand the evolution of the westerly winds, North Pacific Ocean circulation, and East Asian desert landscapes, across the last five million years. In Chapter 1, I reconstruct Pliocene dust fluxes at two different sites in the North Pacific using the constant flux proxy extraterrestrial 3He (3HeET), the first of such records in the Pliocene. Along with 3HeET-derived export productivity fluxes and sea surface temperatures from the westernmost core, I show that the Northern Hemisphere westerly winds, were shifted poleward and weaker during much of the warm Pliocene. Coinciding with the intensification of Northern Hemisphere Glaciation, the westerlies shifted equatorward and strengthened at ~2.7 Ma, and during subsequent glacial periods thereafter. Combining my dust flux record with others from different ocean basin, I find that these changes in the westerly winds were globally synchronous. Chapter 2, entitled “Pliocene Variability of Active Pacific Meridional Overturning Circulation: Reevaluating North Pacific Productivity and Redox Conditions from ~2.5-6 Ma”, presents additional 3HeET-based export productivity flux data, as well as redox element concentrations, from the central subarctic North Pacific through the Pliocene. The new records suggest elevated North Pacific export production during the interval spanning ~4-5.5 Ma, followed by a decrease in the mid-Pliocene (~3.5-4 Ma). Combining this new data with previously published records and modeling output, I provide additional evidence for an active Pacific meridional overturning circulation during the warmer-than-present Pliocene, and add constraints on its variability under various climatic conditions. In Chapter 3, I bring together two constant flux proxy-derived dust flux datasets from the same core in the western North Pacific Ocean to provide novel insight into Quaternary dust dynamics in East Asia. By utilizing constant flux proxies, and accounting for inputs of volcanic material, I show for the first time that dust input to the North Pacific decreased over the last ~2.7 Myr, particularly during glacial periods. While quite different from other previously published dust datasets, this finding is consistent with our current understanding of East Asian dust production mechanisms, and acts as a strong impetus to perform more comprehensive studies of dust fluxes to the North Pacific and other depositional areas downwind of arid regions. Chapter 4 transitions to a terrestrial setting, in which I investigate the impacts of shifting arid region surface albedo on the atmospheric boundary layer using the Hami Basin, China, as a test location. Combining new simulations from the Weather Research and Forecasting base model and available geologic data, I report a previously undescribed “wind-albedo-wind” feedback process. Specifically, I propose that wind erosion, in conjunction with surficial sediments of various albedos, leads to altered wind speeds, and eventually fluctuations in erosion itself. In Chapter 5, I expand upon the work in the preceding chapter by coupling the Weather Research and Forecasting model with a chemistry component to simulate dust emissions. In addition, along with albedo, I characterize previously interpreted surface changes through time to reflect shifts in erodibility and surface roughness. I conclude that although albedo does ultimately influence near-surface wind speeds and dust emissions as predicted in my earlier study, the effects of variable surface roughness and erodibility dominate. Integrating these results with an updated interpretation of the geologic evolution of the Hami Basin, we find that during various periods of the last ~700 ky, the Hami Basin, and likely the greater stony Gobi Desert, could have been much more important dust sources than today.

Located in the far western equatorial Pacific, the Western Pacific Warm Pool (WPWP) is a greater than 10 million km² area of the warmest water on the planet. The WPWP therefore facilitates intense atmospheric convection and participates in coupled ocean-atmosphere climate phenomena such as El Niño Southern Oscillation, regional monsoons, and the shifting Intertropical Convergence Zone. The WPWP is also a water mass crossroads where thermocline-depth western boundary currents (WBCs) such as the New Guinea Coastal Undercurrent (NGCUC) facilitate the transfer of mass, heat, and nutrients vertically, zonally, and meridionally in the ocean. In this dissertation I focus mostly on reconstructing WPWP upper ocean temperature, salinity, nutrient, and productivity dynamics via a suite of physical and geochemical paleoclimate proxies. I apply these proxies in bulk sediments and planktic foraminifera from International Ocean Discovery Program (IODP) Site U1486 over the Pleistocene (2580 ka to 11.7 ka) and Holocene (11.7 ka to present). Site U1486 is located at 2°22’S, 144°36’E in the Bismarck Sea north of New Guinea in the southern WPWP, and is ideally situated to track changes to the WPWP upper water column forced by the South Pacific. The presence of glacial-interglacial (G-IG) variability within WPWP records is particularly important for determining local versus high-latitude climatic influences on the WPWP – with climate shifts such as the mid-Pleistocene Transition (MPT; ~1250 – 700 ka) and mid-Brunhes Event (MBE; ~430 ka) of particular interest in the long-term records I present. In chapter 1, I explore the paleoceanography of the low-latitude Pacific via upper ocean nitrate dynamics. I present a new bulk sediment ẟ¹⁵N record from Site U1486 that spans from 1420 to 0.67 ka – over a million years longer than any nearby records. Via analysis of orbital variability and secular trends at Site U1486 and in records directly along the equator in the Pacific, I find that nitrate dynamics were largely unrelated in the two regions in the Middle and Late Pleistocene. Whereas ẟ¹⁵N at Site U1486 is in line with patterns of eastern Pacific denitrification, increasing ẟ¹⁵N after the MPT at sites located directly along the equator appears linked to increasing Southern Ocean nitrate utilization. Enhanced nitrate utilization is an indicator of a strengthened biological pump – a major contributor to the reduction of atmospheric 𝑝CO₂ during the last glacial. A post-MPT increase in nitrate utilization may therefore point to the Southern Ocean biological pump as a driver for the deeper and longer glacial periods of the 100-kyr world after the MPT. In Chapter 2, I investigate changes in the vertical temperature and salinity structure of the southern sector of the WPWP in relation to the upper ocean’s response to climate change. When combined with Mg/Ca paleotemperatures and δ¹⁸O_sw, my 670-kyr record of Δẟ¹⁸O between the surface-dwelling foraminifera Globigerinoides ruber (sensu stricto) and the thermocline-dwelling foraminifera Pulleniatina obliquiloculata and Globorotalia tumida suggests enhanced thermocline shoaling and a progressively increasing vertical salinity gradient commencing near 240 ka. This secular change in upper water column dynamics does not appear to be associated with previously documented changes in G-IG variability such as the MPT or MBE. Via comparison to other records, I identify widespread cooling of the thermocline in the equatorial Pacific after ~240 ka. After combining these reconstructions with ²³⁰Th-derived focusing factors I validate previous model results indicating obliquity-driven strengthening of low-latitude ocean currents and extend this to imply the periodic increased transport of high-salinity thermocline water masses. These results strengthen previous evidence that the structure of the WPWP thermocline is relatively independent from the drivers of climate at the surface and support that variability in WPWP thermocline circulation is substantially influenced by obliquity. Because of the nitrate dynamics in the Bismarck Sea, bulk sediment ẟ¹⁵N cannot be used to reconstruct productivity. However, chapter 3 constrains variability in productivity via the analysis of new ²³⁰Th-normalized records of preserved biogenic flux and its components at Site U1486 over the last 138 kyr. Here, I assess the drivers of variability in paleo-productivity by reconstructing paleo-stratification, as in the modern Bismarck Sea productivity is stimulated by the delivery of nutrients to the surface during increased upwelling (reduced stratification). Paleo-stratification is approximated by calculating upper ocean density gradients between the calcification depths of G. ruber, P. obliquiloculata, and G. tumida using Mg/Ca temperatures and δ¹⁸O_sw-estimated salinity. Decreased paleo-stratification (a reduced vertical density gradient) was associated with increased productivity and is generally in phase with maximum orbital precession. Paleo-productivity therefore appears to respond to monsoonal increases in coastal upwelling when the Intertropical Convergence Zone (ITCZ) was at its southernmost extent. This illustrates that the unique and more direct method of constraining stratification presented here, which is subject to greater uncertainty, yields results consistent with our current understanding of upper ocean dynamics. I also identify a period between 100 and 60 ka during a potential reorganization of the upper water column in which variability in productivity occurs at a higher frequency than that of precession. Finally, while also related to ITCZ shifts, a nearby record closer to the equator is phase-lagged from Site U1486 – emphasizing the fine-scale regional differences in the drivers of primary productivity in the WPWP.

Master of Science / Department of Geology / Charles G. Oviatt / The Dyer Mountain quadrangle, located in Utah approximately 200 km east of Salt Lake City and 20 km north of Vernal, lies on the south flank of the east-west trending Uinta anticline. The topography of the area varies from mountain peaks to deep canyons, with rolling hills of uplands in between. The elevation in the quadrangle ranges from 3124 m (10248 ft) at the top of Dyer Mountain to 1835 m (6020 ft) at the lowest point of Big Brush Creek. Most of the northern portion of the quadrangle is vegetated by aspens and pines, whereas the southern part of the quadrangle is covered with sagebrush and grasses. Due to its location on the anticline, the quadrangle contains bedrock that dips gently to the south and southeast. The ages of the rocks within the quadrangle range from the Precambrian Uinta Mountain Group to the Quaternary and Tertiary gravels. Also present are the following formations: Cambrian Lodore; Mississippian Madison, Doughnut, and Humbug; Pennsylvanian Round Valley and Morgan; Pennsylvanian to Permian Weber; Permian Meade Peak Member of the Phosphoria and Franson Member of the Park City; and various Quaternary sediments. The Lodore Formation and the Madison Limestone rest on major unconformities, and the Quaternary and Tertiary gravels overlie the Gilbert Peak erosion surface. The Uinta anticline and southerly dip of the Proterozoic and Paleozoic rocks are a result of Late Cretaceous uplift during the Laramide orogeny; Tertiary rocks within the area show little to no deformation. Limestone and various types of ores have been mined in the quadrangle, and phosphorous is currently being mined for fertilizer production. Several landslides, common at the juncture of the Quaternary and Tertiary gravels and Permian shales, were identified within the quadrangle. An anticline and syncline, trending northwest to southeast, lie in the southeast portion of the quadrangle and transect Big Brush Gorge. Geologic hazards of the area include landslides, erosion and failure of road grades, and cliffs near trails. The karst topography of the area presents dangers of sink holes, and evidence of ceiling collapse is present within Big Brush Cave, a popular destination for tourists and cavers.

Troodontidae is an important dinosaur taxon that closely resembles birds in both morphology and biology. The evolution of troodontids is crucial for understanding evolutionary transitions between non-avialan theropods and avialans. Despite the recent discovery of several troodontid taxa across the world and many new studies of coelurosaurian relationships, an overall survey of morphological variation in troodontids and a comprehensive analysis of ingroup troodontid relationships have yet to be accomplished. In the first four chapters of this dissertation, the osteology of two new troodontid taxa and two closely related paravians are described in detail. These descriptions are based on new specimens recovered from the Mesozoic of China and Mongolia. These new taxa include the basal dromaeosaurid Microraptor zhaoianus, the basal avialan Anchiornis huxleyi, a new troodontid taxon represented by IGM 100/1323, and a second new troodontid taxon represented by IGM 100/1126 and IGM 100/3500. These paravian taxa are all small-sized, with a basal paravian body plan resembling Archaeopteryx, yet they represent members of all three major paravian lineages (Troodontidae, Dromaeosauridae and Avialae), and support the traditionally recognized paravian interrelationships. Osteological description of Microraptor zhaoianus is based on an excellently preserved new specimen BMNHC PH881. This specimen preserves significant morphological details that are not present, or are poorly preserved, in the other Microraptor specimens, including aspects of the skull, rib cage, and humerus. These new characters corroborate Microraptor as a member of the Dromaeosauridae and support the close relationship of troodontids with dromaeosaurids. Four new specimens (PKUVP 1068; BMNHC PH804, BMNHC PH822 and BMNHC PH823) of Anchiornis huxleyi reveal new osteological details of this important paravian taxon. Anchiornis huxleyi shares derived features with avialans, but it lacks derived deinonychosaurian characteristics such as a laterally exposed splenial and a specialized raptorial pedal digit II. IGM 100/1323 represents a new troodontid taxon from the Late Cretaceous Djadokhta Formation of Mongolia, diagnosed from other troodontids by the absence of the lateral groove on the dentary, a posteriorly curved pterygoid flange, a distinct spike-like process on the ischium, and elongate chevrons. Despite generally having a basal paravian body plan, IGM 100/1323 displays many derived troodontid features. IGM 100/1126 and IGM 100/3500 represent another new Late Cretaceous troodontid taxon from the Djadokhta-Formation-like rocks at Ukhaa Tolgod, Mongolia. It is unique and distinct from other troodontids in having closely packed peg-like teeth, a twisted suborbital process of the jugal, a quadratojugal with a crescentic ascending process that braces the quadrate posteriorly, reduction of the basal tubera, and presence of a posterior fossa on the proximal fibula. This new taxon is morphologically more derived than Early Cretaceous troodontids but is more primitive than other Late Cretaceous troodontids. A new and comprehensive phylogenetic analysis of coelurosaurian theropods, focusing on troodontids is presented in Chapter 5. This is an updated version of the Theropod Working Group (TWiG) analysis (2015.1). This new analysis incorporates new paravian taxa and new characters, most of which are relevant to paravians, especially the troodontids that are the focus of this dissertation. The new phylogenetic analysis agrees with previous studies on the general relationships of coelurosaurians, yet some important differences from previous TWiG analyses are present in paravians, including: 1), the Jianchang paravians are recovered as basal avialans; 2), Late Cretaceous troodontids form a monophyletic group; and 3), Jinfengopteryginae is not monophyletic.

Detailed geologic mapping of the Deseret Peak East 7.5' Quadrangle yields new interpretations regarding the stratigraphy of the Oquirrh Basin, fault and fold geometry, and structural evolution of the region. The Stansbury Range consists of the north-southtrending Deseret anticline. Basal Mississippian units rest unconformably on Cambrian beds in the central part of the range. Paleozoic uplift, Mesozoic contraction, and Cenozoic extension have created a series of broad folds, large thrust faults, and several normal faults. The area is dominated by bedrock springs, with the presence of abundant and thick Quaternary deposits unrelated to Pleistocene glaciation, burying drainages, and mantling hillslopes. The influence of bedrock on groundwater flow paths and stream baseflow is suggested by local anecdotal reports that high snowfall in the Deseret Peak region generates high discharge ten miles south in Clover Creek, though they are not in the same drainage basin.

The Cowlitz Formation in southern Columbia and Clatsop counties, northwest Oregon was studied in order to prepare a geologic map of parts of this formation and to determine the character of its lithofacies and the environments of deposition.

The Tugaloo terrane in the eastern Blue Ridge, located in the high-grade southern Appalachian crystalline core,contains small internal basement massifs, the Neoproterozoic Tallulah Falls Formation, and Paleozoic granitoid plutons. Detailed geologic mapping in the Lake Toxaway and eastern Big Ridge quadrangles was done to better understand the regional tectonic history. Whole-rock geochemistry was used to determine similarities between the augen phase of the 1.15 Ga Toxaway Gneiss and the 1.15 Ga Wiley Gneiss of northeastern Georgia. The study found that all eastern Blue Ridge orthogneisses are similar and probably share a source. The previously identified Whiteside, Looking Glass, and Pink Beds plutons, and the newly identified Horseshoe Rock and Round Mountain plutons were also characterized. All plutons are low-K, catazonal granodiorites and trondhjemites that plot as volcanic arc or syncollisional granites on tectonic discrimination diagrams. The Looking Glass, Pink Beds, and Round Mountain plutons were dated using U-Pb SHRIMP zircon geochronology, and their ages are 333 + 16 Ma, 371.3 + 4.2 Ma, and 342.5 + 2.4 Ma, respectively. Zircon saturation temperature estimates for these plutons, and a Whitney and Stormer two-feldspar estimate for the Round Mountain pluton, indicate that they intruded at 700-800° C. Whole-rock geochemistry was used to constrain the origin of amphibolites and hornblende gneisses around the Toxaway dome. One sample was a metabasalt with MORB composition, like other eastern Blue Ridge samples. Two other samples have a metasedimentary protolith . Migmatitic aureoles found in the amphibolite facies rocks around the Whiteside, Looking Glass, and Horseshoe Rock plutons are syn-intrusional and represent a zone of contact metasomatism. The new pluton ages constrain the regional deformation history. At least 6 deformations are recognized in the eastern Blue Ridge. Dominant regional foliation is traditionally attributed to the second event (~466 Ma). However, foliations measured within all plutons are identical to foliations measured in the surrounding rock, indicating that foliations had to form after the youngest pluton intruded (~333 Ma), and that Alleghanian deformation was dominant in this region. These observations do not explain cross-cutting relationships observed around older plutons and raise new questions about southern Appalachian tectonics.

With the depletion of the existing reservoirs and the decline in oil discoveries during the last few decades, enhanced oil recovery (EOR) methods have gained a lot of attention. Among the various improved recovery methods, waterflooding is by far the most widely used. However, the presence of reservoir heterogeneity such as high permeability streaks often leads to premature breakthrough and poor sweep resulting in reduced oil recovery. This underscores the need for a prudent reservoir management, in terms of optimal production and injection rates, to maximize recovery. The increasing deployment of smart well completions and i-field has inspired many researchers to develop algorithms to optimize the production/injection rates along intervals of smart wells. However, the application of rate control for other EOR methods has been relatively few. This research aims to extend previous streamline-based rate optimization workflow to polymer flooding and CO2 flooding. The objective of the approach is to maximize sweep efficiency and minimize recycling of injected fluid (polymer/CO2) by delaying its breakthrough. This is achieved by equalizing the front arrival time at the producers using streamline time-of-flight. Arrival time is rescaled to allow for optimization after breakthrough of injected fluid. Additionally, we propose an accelerated production strategy to increase NPV over sweep efficiency maximization case. The optimization is performed under operational and facility constraints using a sequential quadratic programming approach. The geological uncertainty has been accounted via a stochastic optimization framework based on the combination of the expected value and variance of a performance measure from multiple realizations. Synthetic and field examples are used extensively to demonstrate the practical feasibility and robustness of our approach for application to EOR processes.

Copano Bay is a shallow (< 2-3 m), microtidal estuary in south central Texas. In an effort to both determine the distribution as well as investigate the controls on the distribution of oyster reefs, a geophysical survey of Copano Bay was conducted in June and July 2007. Surficial sediment analysis confirms that the recent sedimentation in Copano Bay is comprised of mostly estuarine mud with little sand or shell, large extents of oyster reefs and smaller areas of sand. Seismic stratigraphy analyses verify that the first oyster reefs in Copano Bay formed atop topographic highs in the Pleistocene surface. About 6 ka, sea level rise slowed to near its present rate and sediment supply decreased tremendously to Copano Bay decreasing the amount of suspended sediment. The first oyster reefs began forming around this time using these fluvial terraces as suitable substrate. Once the initial reefs were established, additional reefs began forming atop these initial reefs, or on the eroded shell hash material from the initial reefs. During this time of slow sea level rise and low sediment input to the bay, oyster reefs thrived and reef and shell hash material covered a majority of the bay surface. Once climate change increased sediment input to the bay, the reefs began to decrease in size due to siltation. The reefs have continued to decrease in size causing a 64 percent reduction in oyster reef and shell hash area from approximately 4.8 ka to today.