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New Stratigraphy, Polyphase Deformational History And Basement-Involved Thrust Belt Model For The Proterozoic Uncompahgre Group And Vallecito Conglomerate, Needle Mountains, Colorado, Zinsser Austin

Earth and Planetary Sciences ETDs

The nature and timing of deposition and deformation of Proterozoic siliciclastic metasedimentary cover sequences in the southwestern U.S is important for understanding Paleoproterozoic and Mesoproterozoic tectonism in the context of crustal accretionary episodes. These thick, ultramature siliciclastic successions are important orogenic markers that record regional sedimentation events that occurred between orogenic pulses. Their tectonic connections to these orogenic events remains an important issue. New geologic mapping and structural analysis of the siliciclastic Uncopmpaghre Group and the Vallecito Conglomerate in the Needle Mountains, southwestern Colorado, provide insight into the depositional and deformational history of one of the best exposed of these …

The Case For High-Order, Pleistocene Sea-Level Fluctuations In Southwest Florida, Paul Octavius Knorr

USF Tampa Graduate Theses and Dissertations

Florida's Plio-Pleistocene strata record episodes of sea-level highstands. The age of the strata is often ambiguous as there are no consistently reliable dating techniques that can be unequivocally applied to many of the units. The lack of preservation of continuous Plio-Pleistocene sedimentary sequences is a consequence of Pleistocene mean sea-levels not flooding peninsular Florida, the low volume of sedimentary supply, and the lack of new accommodation space. This study investigates a 6 m cyclothem-type set of six shallow-marine shell beds separated by five subaerially exposed packstone beds. These strata are part of the biostratigraphically-defined early Pleistocene (1.1 --

1.6 Ma) …

Reflectivity Modeling Of A Ground-Penetrating-Radar Profile Of A Saturated Fluvial Formation, William P. Clement, Warren Barrash, Michael D. Knoll

Geosciences Faculty Publications and Presentations

Major horizons in radar reflection profiles may correlate with contacts between stratigraphic units or with structural breaks such as fault surfaces. Minor reflections may be caused by clutter or, in some cases, may indicate material properties or structure within stratigraphic units. In this study, we examine the physical basis for major and minor reflections observed in a shallow, unconfined, fluvial aquifer near Boise, Idaho, U. S. A. We compare a 2D profile from a surface ground-penetrating-radar reflection transect with the 1D modeled reflection profiles at three wells adjacent to the surface-reflection profile. The 1D models are based on dielectric constant …

Investigating The Stratigraphy Of An Alluvial Aquifer Using Crosswell Seismic Traveltime Tomography, Geoff J.M. Moret, Michael D. Knoll, Warren Barrash, William P. Clement

CGISS Publications and Presentations

In this study, we investigate the use of crosswell P-wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers. Our field site was a research wellfield in an unconfined aquifer near Boise, Idaho. The aquifer consists of a ~ 20-m-thick sequence of alluvial cobble- and-sand deposits, which have been subdivided into five stratigraphic units based on neutron porosity logs, grainsize analysis, and radar reflection data. We collected crosswell and borehole-to-surface seismic data in wells 17.1 m apart. We carefully considered the impact of well deviation, data quality control, and the choice of inversion …

Lower Paleozoic Sequence Stratigraphy, Deposystems And Paleogeography Of Northwestern Ordos Basin, North China, Benjamin J. Kessel

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The Ordos basin rests upon the North China Block and is one of the largest sedimentary basins in north China, with more than 15 km of Phanerozoic strata. Published estimates suggest that over 2000 m of carbonates and lesser amounts of siliciclastics were deposited on the North China Carbonate Platform (NCCP) from the Lower Can1brian through the Middle Ordovician. However, lower Paleozoic facies successions and deposystems of northwestern Ordos basin remain poorly represented in western literature. This paper constrains depositional environments, lithologies, facies relationships and sea-level history of the northwestern part of the North China block (NCB) in an effort …

Thermochronology And Provenance Of The Yakutat Terrane, Southern Alaska Based On Fission-Track And U/Pb Analysis Of Detrital Zircon, Stephanie Ellen Perry

Geology Theses and Dissertations

Northward transport of the Yakutat terrane along the Transition and Queen Charlotte-Fairweather transform faults led to Neogene collision of the Yakutat terrane with the southern continental Alaska margin. Northward translation resulted in a stratigraphy that records the erosion of thermotectonic terranes along its path. The strata of the Yakutat terrane includes the Lower Oligocene to Lower Eocene Kulthieth Formation, the Upper Eocene to Lower Miocene Poul Creek Formation and the Miocene-Pleistocene Yakataga Formation. Detrital zircon fission-track (DZFT) ages from stratigraphically coordinated samples collected in the Northern Robinson Mountains yield provenance information of the units that can shed light on their …

Deciphering The Signature Of Magma Mixing: Examples From The Castle Creek Eruptive Period, Mount St. Helens, Washington, Seth Taylor Mattos

All Master's Theses

Mount St. Helens (MSH) volcano in southwestern Washington has intermittently erupted dacitic products for the last 40,000 years. On limited occasions, the volcano has produced andesite lava flows, and during one short-lived period, basaltic lava flows. This time interval has been termed the Castle Creek eruptive period and occurred between approximately 2500 and 1700 years B.P. The Castle Creek period erupted dacite, andesite and basalt within this short span of time. Andesite and dacite eruptions dominate the first approximately 700 years of the period, and all basaltic units were erupted in approximately the last 100 years of the period. This …