Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Geology

2016

Doctoral Dissertations

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

Geomorphology, Stratigraphy, And Paleohydrology Of The Aeolis Dorsa Region, Mars, With Insights From Modern And Ancient Terrestrial Analogs, Robert Eric Jacobsen Ii Dec 2016

Geomorphology, Stratigraphy, And Paleohydrology Of The Aeolis Dorsa Region, Mars, With Insights From Modern And Ancient Terrestrial Analogs, Robert Eric Jacobsen Ii

Doctoral Dissertations

Ancient fluvial features on Mars evidence past episodes of hydrologic activity and paleoclimate conditions suitable for liquid water. The Aeolis Dorsa region preserves the most numerous and diverse assemblage of fluvial features yet observed on Mars and many of these features have experienced a history of burial, exhumation, and topographic inversion. This dissertation describes analyses of visual images and topography of Mars and complementary analyses of fluvial analogs on Earth. These analyses provide information about the styles of fluvial activity, magnitudes of paleodischarge, changes in slope, and inferences about Martian paleoclimate conditions. Results indicate that the Aeolis Dorsa deposits encapsulate …

Go to article

Metamorphic And Structural Control Of Magnetism Within The Lower Continental Crust, Northern Saskatchewan, Canada, Jeffrey R. Webber Nov 2016

Metamorphic And Structural Control Of Magnetism Within The Lower Continental Crust, Northern Saskatchewan, Canada, Jeffrey R. Webber

Doctoral Dissertations

The linking of geophysical information to tectonometamorphic processes holds great potential for the surveying of vast remote areas of the planet and may allow for the transcendence of observational scales. Investigations concerning magnetic properties of the lower continental crust can reveal an incredible wealth of information concerning the conditions of metamorphism, regional extent of deformation, and controls on the magnetic architecture of the lithosphere. This dissertation presents three contributions aimed at the integration of petrology, structural geology, and rock magnetism in order to investigate the magnetic nature of the lower continental crust, constrain tectonometamorphic processes at the regional scale in …

Go to article

Geochemical Attributes Of Hydraulically Active Fractures And Their Influence On Groundwater Quality, Amy L. Hudson Jul 2016

Geochemical Attributes Of Hydraulically Active Fractures And Their Influence On Groundwater Quality, Amy L. Hudson

Doctoral Dissertations

This study utilized discrete interval diffusion sampling of a fractured bedrock well completed in schist to investigate if a natural weathering signal can be used to identify hydraulically active fractures. The open borehole well MFS-1, is the focus of the study, which is in close proximity to the recharge zone making it ideal for testing the hypotheses of this study. The hydraulically active fractures of Well MFS-1 were identified, and the dominant mixing force of the water column of the well was determined to be thermal convection in the upper portion of the well and upward gradients. The isotopic data …

Go to article

Ocean Gateways And Glaciation: Planktic Foraminiferal Records From The Southern Ocean, Equatorial Pacific, And Caribbean, Andrew J. Fraass Jul 2016

Ocean Gateways And Glaciation: Planktic Foraminiferal Records From The Southern Ocean, Equatorial Pacific, And Caribbean, Andrew J. Fraass

Doctoral Dissertations

Ocean gateway changes, once the best mechanism for driving abrupt climatic change, have fallen from favor. They have been largely replaced within the literature by changes in CO2 concentration and orbital forcing. This dissertation looks at three intervals of relative stability (Oligocene), prolonged change (Plio-Pleistocene), or transient events (Oligocene/Miocene boundary) in order to better understand the oceanographic circumstances which govern ‘events’ in the paleoceanographic record. Chapter 1 discusses the chronostratigraphy of Integrated Ocean Drilling Program (IODP) Site U1396 (Expedition 340) in the Caribbean Sea. A combination of paleomagnetostratigraphy, biostratigraphy, astrochronology, and correlation to Marine Isotope Stages (MIS) allows a …

Go to article

A Paleobathymetric Model And Evolution Of The Brazilian Marginal Basins During The Late Maastrichtian To Eocene Based On Benthic Foraminiferal Biofacies, Renata Moura De Mello Jul 2016

A Paleobathymetric Model And Evolution Of The Brazilian Marginal Basins During The Late Maastrichtian To Eocene Based On Benthic Foraminiferal Biofacies, Renata Moura De Mello

Doctoral Dissertations

Benthic foraminiferal biofacies were delimited for the Maastichtian to upper Eocene of five Brazilian marginal basins (Sergipe-Alagoas, Mucuri, Campos, Santos and Pelotas) and two DSDP Sites 356 and 20C of the western South Altantic. Five biofacies, denoted with letters A to E, were defined using Q-mode cluster analysis and correspondence analysis for all of the 11 sites. The benthic foraminiferal biofacies were used to establish a paleobathymetric and paleoenvironmental model for the Brazilian marginal basins. The model tracks the evolution of the margin as it built seaward and transitioned from abyssal (2000-3000 m) to bathyal (m) and neritic (m) depositional …

Go to article

The Role Of Pre-Existing Basement Fabrics In The Initiation Of Continental Rifting: The Okavango Rift Zone, Botswana, Angelica Alvarez Naranjo Jan 2016

The Role Of Pre-Existing Basement Fabrics In The Initiation Of Continental Rifting: The Okavango Rift Zone, Botswana, Angelica Alvarez Naranjo

Doctoral Dissertations

"Integrated geophysical, remote sensing, and field investigations of the Okavango Rift Zone (ORZ), Botswana indicate that a feedback between optimum-oriented basement structures and fluid flow influence the nucleation and growth of continental rifts in their incipient stages. The ORZ, the youngest rift of the East African Rift System, occurs within a Proterozoic inter-cratonic suture zone - the NE-trending Precambrian Damara/Ghanzi-Chobe orogenic belts. The Pleistocene to Holocene ORZ forms a ~450 km long and ~100 km wide half-graben bounded by NE-trending normal faults. Basement units within the Damara/Ghanzi-Chobe orogenic belts exhibit a well-developed NE-trending linear fabric (045-065) defined by parallel limbs …

Go to article

Palynological Studies Of Holocene Lake Sediments In The Missouri Ozarks, Robert D. Haselwander Jan 2016

Palynological Studies Of Holocene Lake Sediments In The Missouri Ozarks, Robert D. Haselwander

Doctoral Dissertations

"Five small lakes in southeast Missouri (Frisco, Pine Forest, and Bray Area lakes [Phelps County], and Cypress and Blue ponds [Bollinger County]) were cored for paleolimnological studies. Cores were evaluated for their sedimentology, palynology, and geochemistry. In two of these lakes (Bray Area and Pine Forest lakes) the planktonic algae were also studied in the water column, along with ecological parameters. Algae in the sediments were compared to algae in the water to understand the resistance of different species to decay, and a suggested methodology for this work is described. Reconstructions of the past environments around each lake were created …

Go to article

Seismic Anisotropy And Mantle Dynamics Beneath The Central And Western United States, Bin Yang Jan 2016

Seismic Anisotropy And Mantle Dynamics Beneath The Central And Western United States, Bin Yang

Doctoral Dissertations

"Various tectonic features and the recent availability of high-quality broadband seismic data from the USArray and other seismic stations in the central and western United States (CWUS) provide a distinct opportunity to test different anisotropy-forming mechanisms. For the first part of the study, a total of 4138 pairs of well-defined shear wave splitting (SWS) parameters observed at 445 stations on the northern Great Plains show systematic spatial variations of anisotropic characteristics. Azimuthally invariant fast orientations subparallel to the absolute plate motion (APM) direction are observed at most of the stations on the Superior Craton and the southern Yavapai province, indicating …

Go to article