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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

Análisis estratigráfico del área de Telsen, provincia de Chubut, Patagonia

Navarro, Edgardo Luis 24 October 2012 (has links)
Un análisis de facies detallado se llevó a cabo en los depósitos fluviales del Grupo Chubut y marinos de la Fm La Colonia que se exponen en el Noreste de la Provincia de Chubut. La Formación Marifil representa las rocas ígneas más antiguas en el área, constituye el basamento sedimentario y perfiles geoeléctricos del subsuelo, determinaron un desarrollo irregular del mismo. Un conjunto de elementos arquitectura-les caracterizan al sistema fluvial del Grupo Chubut: lacustre expuesto sólo al norte, y elementos de canal, faja de canales y de llanura de inundación al sur. Estos últimos, presentan una progresiva variación desde abanicos aluviales en la base, sistemas entrelazados y sistemas de canales arenosos en cinta, depositados en sucesivos episodios con depósitos de desborde. En el tramo superior de la sucesión se reconocieron cinturones meandrosos poco desarrollados y canales aislados, culminando con un importante desarrollo de elementos de llanura de inundación. Asociado a los depósitos de llanura de inundación, se reconocieron rasgos post-depositacionales vinculados con procesos de licuefacción/fluidización, rela-cionados con una etapa de telodiagénesis. Una sucesión vertical de 4,5 m, comprende cuatro intervalos bien definidos: fragmentado in situ, brechado, brechado fango sostenido y superior homogéneo, con potenciales conductos de escape, Constituyen un ejemplo excepcional de desarrollo natural de brechamiento en un medio frágil y los mecanismos dispara-dores podrían estar asociados a actividad sísmica o a impacto de bólidos. A partir del análisis de circones detríticos, se determinó para el Grupo Chubut una edad máxima de deposi-tación albiana, ca. 106 Ma en la localidad de Telsen y ca. 109 Ma en el sector Cañadón Williams. Las fuentes de procedencia para el Grupo corresponden principalmente a la Formación Marifil, cuya edad quedó acotada para el área entre 182 y 188 Ma. La comparación de los datos jurásicos en las dos muestras analizadas, sugiere una modificación progresiva desde el NE al E-SE del sector de aporte al Grupo Chubut. En contacto neto erosivo sobre el Grupo Chubut, se dispone asociado a la Fm La Colonia, un conglomerado tabular basal, que representa una superficie de ravinamiento, de impor-tancia significativa en la estratigrafía secuencial. Fue interpretada como una superficie transgresiva que evidencia para el área de Telsen el comienzo de la ingresión maastri-chtiana. Le suceden hacia arriba, asociaciones de facies de frente de playa a off shore, intermareal (llanura mixta y llanura fangosa), lagunas con influencia marina y lagunas sin aparente conexión marina en el sector supramareal, con esporádicas intercalaciones arenosas con estructura de domo y cuenco en la base. Se indicaron para la Fm La Colonia ambientes restringidos de baja energía, asociados a una costa fangosa, afectada por episodios de tormenta. Considerando el hiato que media entre el Grupo Chubut (Albiano) y Fm La Colonia (Maastrichtiano/Daniano), se propone considerar como Formación La Colonia, al conjunto de pelitas verdosas a grisáceas, de origen marino, ubicadas por encima de la super-ficie transgresiva, mientras que las pelitas continentales por debajo de esta superficie, hasta el momento pertenecientes a la Fm La Colonia, quedarían incluidas en el Grupo Chubut. Una discontinuidad de bajo ángulo, con una inclinación de aproximadamente 0.5%, que trunca al Grupo Chubut y a la Formación La Colonia fue reconocida en el área. Un mapeo de semidetalle de las unidades geológicas y un mapeo de detalle de los paleoambientes, complementan la información cartográfica preexistente. / A detailed facies analysis was performed on the fluvial deposits of the Chubut Group as well as on the marine deposits of La Colonia Formation, both located at Northeast-Chubut Province. The Marifil Formation represents the older igneous rocks in the area, constitutes the sedimen-tary basement and geolectric profiles determined an irregular morphology for the subsurface deposits of the unit. The fluvial system of the Chubut Group is characterized by a number of architectural elements: lacunar in the North, and channel, channel belt and floodplain elements in the South. The last elements, as exposed in a vertical succession, vary progressively from alluvial fans in the bottom, braided systems and multistorey sandstone- dominated ribbon channels with crevasse splay deposits. The upper part of the succession evidences poorly developed meander belts and isolated channels, ending with a significant development of the flood-plain elements. Post-depositional features recognized in the floodplain deposits evidence liquefaction/fluidization pro-cesses and they were associated with a telodiagenetic stage. The 4,5m vertical succession comprises four well-defined intervals: fractured, brecciation, mud-rich breccias and upper fully shared, including potential escape conduits. They represent an exceptional example of naturally developed brecciation in a brittle medium. These processes may have been originated by seismic activity or bolides impact. The analysis of detrital zircon yielded the Aptian as the maximum depositional age for the Chubut Group, ca. 106 Ma in Telsen, and ca. 109 Ma in the Cañadón Williams area. The sources for the Chubut Group correspond mainly to the Marifil Formation, whose age in the area was restricted between 182 and 188 Ma. Comparing the Jurassic data in the two samples analyzed, suggests a progressive modification of the Chubut Group source area from the NE to E-SE. Associated to the La Colonia Formation deposits, a basal tabular conglomerate, lying in sharp erosive contact with the Chubut Group, repre-sents a ravinement surface and constitutes a key surface from a sequence stratigraphy approach. It was interpreted as a transgressive surface and evidences the beginning of the Maastrichtian ingression for the area. Upwardly, this surface is succeeded by facies associations related to shoreface to offshore, intertidal (mixed and mud flat), lagoons under marine influence and lagoons with no apparent marine relation in the supratidal zone. Low-energy restricted environments, associated with a muddy coast affected by storm episodes, were interpreted for the La Colonia Formation. Taking into account the hiatus between the Chubut Group (Albian) and the La Colonia Formation (Maastrichtian/Danian), is herein proposed, that the latter ought to be associated with the set of marine greenish-gray mudstones on top of the trans-gressive surface, while the continental mudstones under this surface -related up to now to La Colonia Formation- should be included in the Chubut Group. A lowangle discontinuity that cut across the Chubut Group and La Colonia Formation, of about 0.5%, was recognized in the area. A semi-detailed mapping of the geological units and a detailed-mapping of the palaeoenvironments, complement the cartographic information available.
582

High-Resolution Sequence Stratigraphy of Paleogene, Nontropical Mixed Carbonate/Siliciclastic Shelf Sediments, North Carolina Coastal Plain, U. S. A.

Coffey, Brian Perry 28 January 2000 (has links)
The sequence stratigraphic development of the subsurface Paleogene, Albemarle Basin, North Carolina, was defined using well cuttings and wireline logs tied into largely published biostratigraphic and available seismic data. Facies include: silty and shelly sands and shell beds (estuarine/lagoon/protected inner shelf facies); clean quartz sands and sandy mollusk-fragment grainstones (shoreface/shallow shelf); phosphatic hardgrounds (current and wave-swept shoreface and shallow shelf); bryozoan and echinoderm grainstones/packstones (storm reworked middle shelf); and fine skeletal wackestones and planktonic marls (slightly storm-winnowed to sub-wave base, deeper shelf). Paleogene deposition on this high-energy, open-shelf was characterized by a distinctive shelf profile of inner shelf and inner shelf break, deep shelf and continental shelf/slope break. The successive positions of terminal supersequence inner-shelf-breaks parallel the modern day continental margin and its onshore arches. Thickness trends were strongly controlled by more rapid subsidence within the Albemarle Basin. The Paleocene supersequence is dominated by deep shelf marl and developed following flooding after the latest Cretaceous low-stand. Major shallowing occurred at the end of the Early Paleocene and near the end of the Late Paleocene. The Eocene supersequence developed following lowstand deposition (evident on seismic) just off the terminal Paleocene depositional shelf break. With flooding, a major transgressive sediment body developed (Pamlico spur), that formed a 50 km wide by 50 m high promontory at the inner shelf break, followed by HST progradation of quartzose and bryozoan-echinoderm open shelf carbonates that filled in the laterally adjacent shelf topography. This was followed by ancestral Gulf Stream incision of the southeast-trending, shallow shelf to the south, and deep shelf further northeast. Late Eocene-Oligocene deposition was initiated with localized lowstand sedimentation off the earlier terminal inner shelf break, followed by thin regional marl deposition and widespread highstand inner shelf, quartz sands and quartzose carbonates. Localized Late Oligocene lowstand deposition occurred along the earlier Oligocene terminal inner shelf break, followed by widespread deposition of quartzose facies over the shallow shelf. Oligocene units on the deep shelf were modified by highstand Gulf Stream scour. / Ph. D.
583

High-Resolution Sequence Stratigraphy of Late Mississippian (Chesterian) Mixed Carbonates and Siliciclastics, Illinois Basin

Smith, Langhorne Bullitt 20 May 2008 (has links)
Eight 4th-order (~400 k.y.) disconformity-bounded mixed carbonate-siliciclastic sequences were deposited in the tectonically-active, tide-dominated Illinois basin during the Late Mississippian greenhouse to icehouse transition. Detailed, lithologic cross-sections were constructed through the Chesterian Ste. Genevieve through Glen Dean interval which show an upward change in character from carbonate-dominated sequences bounded by caliche and breccia paleosols to mixed-carbonate siliciclastic sequences bounded by red, slickensided mudrock paleosols and incised valleys. The 4th-order sequences are composed of 5th-order parasequences that can be correlated basin-wide. Parasequences in the basal, dominantly carbonate sequences are composed of patchy ooid grainstone tidal ridge reservoir facies which interfinger with skeletal limestone and are capped by laterally extensive muddy carbonate units. Parasequences in the overlying mixed carbonate siliciclastic interval commonly have basal quartz sandstone valley fill and tidal sand ridge reservoir facies overlain by skeletal limestone and shale-dominated siliciclastics. The sequences can be bundled into sequence pairs and composite sequences. Composite sequences are composed of 4 sequences and are bounded by better developed disconformities that commonly coincide with biostratigraphic zone boundaries. High energy reservoir facies are widespread in transgressive sequence tracts and late highstand sequence tract (where present) and confined to updip areas in the early highstand sequence tracts. Increasing amplitude 4th-order glacio-eustasy produced the sequences and caused the upward increase in incised valleys and deeper water carbonate deposition. Parasequences were produced by 5th-order glacio-eustatic sea-level fluctuations (20-100 k.y.). Sequence pairs and composite sequences were produced by 3rd-order sea-level fluctuations possibly in combination with local tectonics. Spatial and temporal variations in differential subsidence between the eastern and western shelves and the more rapidly subsiding basin interior caused variations in onlap/offlap geometries of sequences and parasequences. Increasingly wetter wet-dry seasonality caused an upward increase in siliciclastic influx and concurrent decrease in ooid deposition. The increasing-amplitude eustasy and progressively more humid climate were caused by the onset of continental glaciation on Gondwana. / Ph. D.
584

Sequence Stratigraphy and Chemostratigraphy Across the Permo-Triassic Extinction Event, Upper Khuff Carbonates, Ghawar Field, Saudi Arabia

Al-Dukhayyil, Raed Khalil 07 June 2012 (has links)
Logging of cores of the Upper Permian and Lower Triassic Khuff Formation, Ghawar, Saudi Arabia, has allowed a high resolution sequence stratigraphic framework to be generated. The lithofacies of this huge, arid epeiric ramp succession include: subaqueous -and supratidal anhydrite, tidal flat laminites, lagoonal mudstone, ooid-peloid grainstone, and subtidal off-shoal open marine mudstone. Third order sequences include the Late Permian upper Khuff C, the Early Triassic Khuff B and the Khuff A sequences, which corrrelate with global cycles. Seven high frequency sequences (HFSs) make up the Changhsingian upper Khuff C. These HFSs are ~400 k.y. duration and probably driven by long term eccentricity. The Early Triassic Khuff B and A sequences are made up of 4 HFSs each, which appear to be ~100 to 200 k.y. duration and not easily tied to eccentricity forcing. The HFSs are in turn composed of parasequences, which appear to be 10 to 20 k.y. average durations, suggesting precessional and half precessional forcing. However, many thin locally developed cycles may be autocycles or subprecessional cycles. Sequence stratigraphic cross sections and facies maps document progradation directions on the platform, reflecting the subtle interplay between the Ghawar structure and regional paleoslopes. Anhydrites are rare in the Permian Upper Khuff C except near the base of the studied interval. Anhydrites are well developed in the Triassic Khuff B and Khuff A where some form transgressive deposits while others are highstand deposits of high frequency sequences. The Permian-Triassic boundary (PTB) on the Arabian Platform marks a significant relative sea-level drop, that exposed from the outcrop belt to somewhere east of Ghawar. This contrasts with transgressive PTB settings elsewhere. Across the PTB the mass extinction is marked by a major decrease in biotic groups. The extinction was followed by development of subtidal thrombolites and increased microbial calcification due to decreased bioskeletonization. The dominant reservoirs in the Permian Upper Khuff C occur in oolite in the uppermost high frequency sequence. In the Triassic Khuff B and A the reservoir facies are commonly non-dolomitized oolitic facies associated with open lagoon carbonates distant from evaporitic tidal flats. Within dolomitized units, best reservoirs are associated with oomoldic porosity, but oolite units proximal to evaporitic tidal flats have porosity plugged by anhydrite. Carbon and oxgyen isotope profiles up to 150 m long were obtained from cored wells of the Khuff Formation, Ghawar Field, Saudi Arabia, across the Permian-Triassic boundary. Major global excursions are at the Changhsingian-Wuchiapingian boundary and the Permian-Triassic boundary, but several smaller excursions also appear to correlate with excursions elsewhere. The presence of the negative C-isotope excursions globally in both δ¹³Ccarbonate and δ¹³C organic as well as in deeper water sections lacking emergence surfaces, strongly supports the idea of these excursions being global phenomena related global C cycling. Over 75% of the negative carbon isotope excursions in Ghawar occur beneath emergence surfaces, including the two major excursions at the Wuchiapingian and Changhsingian stage boundaries. The δ¹³C profiles beneath the boundaries resemble those iii associated with early diagenesis associated with isotopically light soil gas. The δ¹⁸O profiles beneath the surfaces are variable, perhaps reflecting variable effects of evaporation on the meteoric input, mixing or overprinting by burial diagenesis. This suggests that the C-isotope excursions on the Arabian Platform, although global in origin, appear to have been modified by early diagenesis. U depletion across the boundary is compatible with the postulated origins of the PTB event with bottom waters becoming stagnant and reducing, as a result of warming induced by volcanogenic CO₂ released by Siberian trap volcanism, methane release from thermal metamorphism of coals and destabilization of clathrates in the deep sea due to ocean warming. The global extent of the C-isotope and U excursions provides a high resolution correlation tool for Late Permian and Early Triassic successions. / Ph. D.
585

Sequence stratigraphy and the development of a clinoformal carbonate ramp on an abandoned delta system: Mississippian Fort Payne--Salem Interval, Kentucky

Khetani, Amy B. 01 November 2008 (has links)
Middle Mississippian ramp carbonates in Kentucky (Fort Payne to Salem interval) form a large scale depositional supersequence (0 to 500 feet thick, approximately 8 m. y. duration). It formed on and in front of the abandoned Early Mississippian Borden deltaic marine paleoshelf, which had up to 100 m of relief above the adjacent starved basin. Major facies consist of marine quartz sandstone and shale; peritidal carbonates; high-energy ramp margin, crinoidal-bryozoan grainstones; deeper ramp mounds, skeletal grainstone/packstone sheets and channel-fills interlayered with shale or calcisiltite; and slope deposits of siliceous calcisiltite. Regional slopes on the paleoshelf edge and ramp margin are 0.5 to 2.5 mIkm (less than 0.25 degrees), although clinoforms of 2 to 10 degrees occur locally associated with mounds and depositional lobes. The supersequence LST is dominated by mounds interlayered with green shaly, deeper ramp facies. The mounded units are located in a fairway that is normal to the Borden margin but parallel to the Appalachian Grainger deltaic shelf. No TST is evident, except for a glauconite horizon capping the Borden paleoshelf. The supersequence HST consists of at least eight third-order sequences (each approximately 1 m.y. duration), the older ones downlapping onto the shelf 20 to 30 m deep, the younger ones downlapping into the deeper basin (over 150 m water depth). Sequences show marked toplap with the upper sequence boundary. The third-order sequences locally have lowstand sands, some of which may be associated with a paleodrainage system off the Borden paleo shelf. They lack recognizable TSTs, but have well-developed prograding HST units of nearshore shale and peritidal dolomite, skeletal packstone/grainstone banks, and siliceous calcisiltite slope facies. The supersequence correlates with a global sea level cycle in the lower Visean terminating in a major sea-level fall. The highly clinofonned toplapping supersequence reflects this long term, sea-level fall which prevented space from being created on the old delta top. The third-order sequences, although mappable between the sections, are not easily correlated with global third order cycles. / Master of Science
586

Quantitative approaches and applications to the sequence stratigraphy and biodiversity of Pleistocene – Holocene mollusk communities from the Po plain, Italy and San Salvador Island, the Bahamas

Wittmer, Jacalyn M. 26 March 2014 (has links)
The following chapters presented here use modern ecological data and modern marine systems to evaluate past marine depositional settings and the preservation potential of various environments in the geological record. While the chapters in this dissertation vary in terms of study area, sedimentary systems (carbonate vs. siliciclastic), depositional environment, and organisms, all projects are based on developing and using quantitative models to evaluate the present as a means for understanding the past. Chapter one focuses on the preservation potential of rocky intertidal environments. The rocky intertidal zone is one of the most poorly preserved fossil-rich environments in the geological record. However in most coastal marine habitats today, it is one of the most diversity rich environments. Chapter one also focuses on the analytical advantages of hierarchical sampling of gastropod communities across San Salvador Island, the Bahamas to quantify community and species level preservation potential in rocky shore environments. Chapters two and three are based on the fossil-rich sedimentary deposits from the Po coastal plain in northeastern Italy. These deposits have been widely studied in terms of their sedimentology and stratigraphy, resulting in a highly resolved sequence stratigraphic architecture. The integration of sequence stratigraphy with paleobiology can enhance our understanding of spatiotemporal biotic patterns recorded in the fossil record. Used in conjunction with the highly-resolved stratigraphic framework, biotic patterns can be used to assess depositional cycles and bathymetry through time. Chapter two integrates sequence stratigraphic patterns and paleoecological data to develop bathymetric models across fossiliferous marine successions of the Po coastal plain, Italy. Chapter three evaluates the modern ecological dataset used to derive the bathymetric models. The last chapter also explores water depth distribution for selected taxa recorded in the Quaternary sediments and observed in present-day habitats. The dissertation research explored here demonstrates that modern ecological systems are essential to evaluating past geologic events. Through direct observation and quantitative analysis, I have learned that modern and fossil communities behave differently depending on environment (e.g. energy, salinity, water depth, etc.). These variables affect the distribution of living organisms today and through my research, delineate fossil distributions through time. With these observations, new questions have arisen about the latitudinal variability of rocky intertidal fossil preservation and extrapolating the quantitative bathymetric models to deeper time intervals. These questions will lead to future endeavors and pointedly add to the field of geology and stratigraphic paleobiology. / Ph. D.
587

Cenozoic Variations in the Deep Western Boundary Current as Recorded in the Seismic Stratigraphy of Contourite Drifts, Newfoundland Ridge, Offshore Canada

Boyle, Patrick Ryan 03 June 2014 (has links)
A contourite drift complex on the J-Anomaly Ridge (JAR) and Southeast Newfoundland Ridge (SENR), offshore eastern Canada, records an extensive archive of North Atlantic circulatory and sedimentary dynamics formed under the influence of the Deep Western Boundary Current (DWBC). Seismic-reflection profiles constrained by drill sites from IODP Expedition 342 are used to map the spatial and temporal distribution of contourite sedimentation and to evaluate the Cenozoic history of the DWBC within a preexisting climatic framework. This study indicates three phases of sedimentation termed here Pre-Contourite-Drift Phase (~115-50 Ma), Active-Contourite-Drift Phase (~50-2.6 Ma), and Post-Contourite-Drift Phase (~2.6-0 Ma). Bottom current controlled sedimentation began at the boundary between Pre-Contourite-Drift Phase and Active-Contourite-Drift Phase (~50 Ma), and correlates to a long-term global cooling trend that initiated at the end of the Early Eocene Climatic Optimum. Within the Active-Contourite-Drift Phase at ~30 Ma depocenters shifted deeper and current energy and focus is interpreted to have increased in association with global oceanographic change at the Eocene-Oligocene transition. The beginning of Post-Contourite-Drift Phase sedimentation (~2.6 Ma) marks a shift in bottom current path towards shallower water depths, and corresponds with the onset of Northern Hemisphere ice sheets. These events of circulatory reorganization correlate with other North Atlantic seismic stratigraphic studies, suggesting that these events occurred throughout the North Atlantic. An improved understanding of long-term (>1000000 yr) dynamics of North Atlantic circulation in response to significant reorganization of Cenozoic climate provides important context towards refining models and prediction of oceanic response to contemporary climate change. / Master of Science
588

Middle-Hauterivian to Lower-Campanian sequence stratigraphy and stable isotope geochemistry of the Comanche platform, south Texas

Phelps, Ryan Matthew, 1982- 11 July 2012 (has links)
Carbonate platforms contain a wealth of information regarding the changing biota, sea level, ocean-chemistry, and climate of the Cretaceous Period. The Comanche platform of the northern Gulf of Mexico represents a vast, long-lived carbonate system that extended from west Texas through the Florida panhandle. In central and south Texas, excellent outcrops and an extensive suite of subsurface data provide an opportunity to document the evolution of this system, from the shoreline to the shelf-margin and slope. This study examines the changing facies, platform morphologies, and shelf-margin architectures of the mixed carbonate-siliciclastic, middle-Hauterivian to lower-Campanian interval. Stratigraphic results are integrated with stable-isotope geochemistry to document the detrimental effects of oceanic anoxic events on the carbonate platform. Seven second-order, transgressive-regressive supersequences of 3-14 Myr duration are defined in south Texas using sequence stratigraphic analysis of shelf-interior facies successions. Second-order supersequences are subdivided into several third-order depositional sequences of 1-3 Myr duration. In these sequences, facies proportions and stratal geometries of the shelf-interior are found to be the result of changing platform morphology and temporal evolution from distally-steepened ramp to rimmed-shelf depositional profiles. Shelf-margin trajectories, stratigraphic architectures, and facies proportions are a function of long-term accommodation trends expressed in second-order supersequences. These characteristics are modified by lateral variability in the underlying structural/tectonic setting and localized syndepositional faulting. The stratigraphic equivalents of oceanic anoxic events 1a, 1b, 1d, 2, and 3 are documented in the Cretaceous section of south Texas. These oceanic anoxic events coincided with maximum flooding zones of supersequences and are linked to carbonate platform drowning events on four separate occasions. The occurrence of oceanic anoxic events is found to be a fundamental driver of carbonate platform morphology, faunal composition, and facies evolution in transgressive-regressive supersequences of the northern Gulf of Mexico. / text
589

DATA MINING AND VISUALIZATION OF EARTH HISTORY DATASETS FROM GEOLOGICAL TIMESCALE CREATOR PROJECT

Abdullah Khan Zehady (8790095) 04 May 2020 (has links)
<p>The Geologic <i>TimeScale Creator </i>(TSCreator) project has compiled a range of paleo-environmental and bio-diversity data which provides the opportunity to explore origination, speciation and extinction events. My PhD research has four major interconnected themes which include the visualization methods of evolutionary tree and the impacts of climate change on the evolution of life in longer and shorter timeframes: <b>(1) </b>Evolutionary range data of planktonic foraminifera and nannofossils over the Cenozoic era have been updated with our latest geological timescale. These evolutionary ranges can be visualized in the form of interactive, extensible evolutionary trees and can be compared with other geologic data columns. <b>(2) </b>A novel approach of integrating morphospecies and lineage trees is proposed to expand the scope of exploration of the evolutionary history of microfossils. It is now possible to visualize morphological changes and ancestor-descendant lineage relationships on TSCreator charts which helps mutual learning of these species based on genetic and bio-stratigraphic studies. <b>(3) </b>These evolutionary datasets have been used to analyze semi-periodic cycles in the past bio-diversity and characteristic rates of turnover. Well-known Milankovitch cycles have been found as the drivers of fluctuations in the speciation and extinction processes. <b>(4) </b>Within a shorter 2000-year time period, global cooling events might have been a factor of human civilization turnover. Using our regional and global cultural turnover time series data, the effect of climate change on human culture has been proposed. The enhancement of the evolutionary visualization system accomplished by this research will hopefully allow academic and non-academic users across the world to research and easily explore Earth history data through publicly available TSCreator program and websites. </p>
590

IDENTIFICATION OF ANCIENT ENVIRONMENTS AND THEIR RELATED GEOLOGIC PROCESSES ON MARS USING REMOTE SENSING TECHNIQUES

Amanda Rudolph (16636299) 02 August 2023 (has links)
<p>The present-day sedimentary rock record on Mars provides insights into the early surface and subsurface geologic processes. Understanding the sediment characteristics in different environments can help to constrain the climate regimes, potential for habitability, and provide a record of ancient surface processes. The research presented in this dissertation uses complementary remote sensing techniques and datasets from rovers at the surface, satellites in orbit, and at terrestrial analogs that are relevant to current Mars exploration to better characterize alteration through water-rock alteration at multiple scales.</p><p>The martian field site for this work is Mt. Sharp, a 5-kilometer-high mountain in Gale crater that is predominantly composed of fluviolacustrine strata overlain by aeolian strata. At the rover-scale, the effects of large clay-mineral rich deposits were characterized using landscape- and hand lens-scale visible images from the Mastcam and MAHLI instruments, and multispectral visible/near-infrared images from Mastcam (445-1013 nm). Detailed analysis of the observed textures and spectral properties showed that the clay-rich deposits preserve the early surface environment, based on their lack of diagenetic features. While the regions immediately surrounding the clay-rich deposit experienced prolonged exposure to water, leading to enhanced alteration zones, and destroying characteristics from the early environment but providing insight into later water-rock processes.</p><p>At the orbital-scale, three visually distinct, dark-toned, and erosion-resistant layers were mapped and characterized using visible to short wave infrared hyperspectral (700-2650 nm) and image data. Two of these units have been identified as either aeolian or lacustrine through in situ rover investigations and the third unit will not be explored in situ so its origin can only be constrained through orbital analyses. We conducted a comparison of the morphological and spectral properties of the two known units to constrain whether their respective environments can be differentiated from orbit and apply this knowledge to the unknown third unit. The composition of all three units is similar, dominated by mafic minerals, suggesting a similar sediment source. The morphology is distinct between the lacustrine and aeolian units, with the unknown unit having similar morphology as the lacustrine unit, suggesting similar environments. We propose that the lacustrine unit in this study likely represent short-timescale transitions between wet and dry environments, where mafic sands are exposed to water prior to burial and lithification. While in the aeolian unit, most water-rock interactions occur upon lithification and later diagenesis. This has climatic implications in terms of the presence of surface water as these units were deposited as part of the original Mt. Sharp strata (i.e., the lacustrine unit) while some mantling existing topography (i.e., the aeolian and unknown units), representing similar processes but at a much later time.</p><p>The terrestrial analog field site for this dissertation was conducted in Iceland which represents a cold and wet/icy climate. We characterized sediments produced through glaciovolcanism and how they are sorted and altered through transport from source to sink along to characterize unique identifiers of glaciovolcanism that can be determined with Mars-relevant techniques. Decorrelation stretched visible images and lab visible/near-infrared reflectance and thermal-infrared emission data sets (400-2500 nm and 1200-400 cm-1, respectively) show that it is possible to differentiate sediments from glaciovolcanic and subaerial volcanic systems. In some glaciovolcanic systems, a high glass abundance (50-90 %) is observed in sediment grains due to the erosion of hyaloclastite and hyalotuff, deposits that form in water- and ice-magma interactions. These glass grains did not readily breakdown physically or chemically during transport, suggesting that they could still be observed on the martian surface today and be used to identify possible glaciovolcanic deposits.</p><p>The research described in this thesis improves the understanding of different geologic environments using remote sensing techniques and their climatic implications. This will help to better constrain early environments on Mars and identify areas where water may have been present through the rock record, as observed from the surface and from orbit.</p>

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