Physical Sciences and Mathematics Commons^™

Calcareous Nannofossil Biostratigraphy And Paleoecology Of The Fort Hays Limestone Of Western Kansas, Western Interior Basin (Wib), Bryan Hermosillo

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Investigations of Upper Cretaceous hemi-pelagic sediments from the Western Interior Basin suggest that high surface water fertility caused increased production of biogenic carbonate, resulting in the deposition of limestone. We examined calcareous nannofossils from the Turonian/Coniacian Fort Hays Member of the Niobrara Formation to evaluate the correlation between nannofossil surface water fertility proxies and associated lithology. Our paleoecology results indicate that oligotrophic surface water conditions were present during limestone deposition. This stands at odds with existing depositional models for the Western Interior Seaway (WIS). Paleoecological data within the interbedded marls was artificially skewed due to the prevalence of etching caused …

Quantification Of Cloud Condensation Nuclei Effects On The Microphysical Structure Of Continental Thunderstorms Using Polarimetric Radar Observations, Kun-Yuan Lee

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Aerosols serving as cloud condensation nuclei (CCN) are crucial to the microphysical structure of thunderstorms. They can also alter the rate of cloud microphysical processes, the moisture profile and the local temperature as a result of latent heating/cooling in the early stage of thunderstorm development. Continental thunderstorms are characterized by high complexity and are highly influenced by environmental conditions. The purpose of this study is to determine the influences of CCN concentration on the microphysics of continental thunderstorms, using a sample of storms from northwestern Oklahoma. The Weather Surveillance Radar-1988 Doppler (WSR-88D) at Vance Air Force Base (KVNX) was upgraded …

A Quantitative Analysis Of Calcareous Nannofossils Across A Late Oligocene Paleolatitude Transect Of The North Atlantic Ocean, William Barrett Clark

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Samples from ODP Sites 926, 628, 563, U1406, 647, and 918, were analyzed quantitatively across a paleolatitude transect of the North Atlantic Ocean to determine the paleolatitudinal distribution of calcareous nannofossils in the Late Oligocene and the effects of that distribution on biostratigraphic resolution. Detrended Correspondence Analysis (DCA), a Temperature index (TI), and the Shannon Diversity Index (H), were used to examine the paleoenvironmental gradients which exerted the most control over the distribution of species and their abundances. The temperature index correlates significantly to the first axis of the DCA, suggesting that thermal controls were the most important factor in …

Quantifying The Distribution And Mechanisms Accommodating Penetrative Strain Along The Western Margin Of The Laramide Denver-Julesburg Basin, Marques Hatfield

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Grain-scale volume loss is an important process in the deformation of a fold-thrust belt. Prior to activation of slip on fault surfaces, and initiation of layer buckling in folds, instability is recorded by thickening of parallel bedding surfaces, grain boundary migration, and stress-induced solution transfer of mineral grains. Volume loss recorded by these mechanisms is significant but is an afterthought in any type of cross-section restoration.

This research has three main objectives. Firstly, to estimate the amount of penetrative strain (PS) accommodated in weakly deformed sandstones along four E-W transects, from the thick-skinned Colorado Front Range into the Denver-Julesburg Basin. …

Numerical Modeling Of The Effects Of Land Use Change And Irrigation On Streamflow Depletion Of Frenchman Creek, Nebraska, Moussa Guira

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

A three-dimensional Control Volume Finite Difference-based numerical groundwater flow model was constructed to assess the effects of agricultural irrigation and land use change on streamflow depletion. The study area is Frenchman Creek basin located in southwestern corner of the State of Nebraska, USA. This area was subject to an increased proliferation of groundwater abstraction for agricultural purposes since industrial revolution. It has also been subject to land use change from native rangeland to dry and irrigated cropland. The groundwater flow model was spatially discretized using Voronoi cells in unstructured grid built with the USGS MODFLOW-6. Temporal discretization defined 151 time …

Isotopic And Geochemical Analysis Of Nitrate Contaminated Groundwater In Edgar, Nebraska, Nathan Roddy

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

High nitrate concentrations in the groundwater beneath Edgar, Nebraska have been measured for well over a decade, exceeding the EPA’s MCL of 10 mg-N/L. Investigating the isotopic signature of nitrate and groundwater have determined the likely source(s) of contamination. Apparent seasonal changes exists in nitrate concentration, isotope ratios, and geochemistry, suggesting that sources and flow paths change as a result of irrigation. Samples collected in December and May had very similar nitrate concentrations (average value of 13.7 mg-N/L) and isotopic ratios (δ¹⁵N 4.46‰ and δ¹⁸O-NO₃ 20.21‰), suggesting synthetic nitrate fertilizers are the major source of …

Evaluating 21st Century Climate Change For Bolivia: A Comprehensive Dynamical Downscaling Strategy Using The Wrf Regional Climate Model, Azar Mohammad Abadi

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Bolivia is a low-latitude, developing country at grave risk for the effects of human-induced climate changes. This means evaluating the consequences of projected future climate changes is of significant importance. Unfortunately, the complex topography and high elevation of much of the country pose particular challenges, as these effects cannot be suitably resolved at the approximately 100 km spatial resolution of current global climate models (GCM). Therefore, a comprehensive suite of high-resolution climate change simulations was made focused on Bolivia are run using three different GCMs with three different emission scenarios for each to drive the Weather Research and Forecasting (WRF) …

Road Weather Impact Based Decision Support Applications: Developing A Department Of Transportation Winter Severity Index, Curtis Louis Walker

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Adverse weather conditions are responsible for millions of vehicular crashes, thousands of vehicular deaths and billions of dollars in economic and congestion costs. Many transportation agencies utilize a performance or mobility metric to assess how well they are maintaining road access. This research focuses on the development of a winter severity index for the State of Nebraska (NEWINS). NEWINS is an event-driven index that was derived for the Nebraska Department of Transportation (NDOT) and its districts across the state. The NEWINS framework includes a categorical storm classification framework and climatological aspect to capture atmospheric conditions more accurately across diverse spatial …

Neogene Stratigraphy And Paleoenvironments In The Lauca Basin Of Northern Chile, Amanda Jones

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

This thesis examines a late Miocene to Pliocene sedimentary succession in the Lauca Basin, a topographically isolated, fluvio-lacustrine basin in the northern Chilean Altiplano. A sedimentary section within the Lauca Basin, composed of Lauca Formation sediments, was investigated using stratigraphic and petrographic analyses to define the Miocene to Pliocene paleoenvironmental history of the region. Geochronologic results indicate the section ranges in age from approximately 5.57 +/- 0.20 Ma to 5.44 +/- 0.16 Ma. The sedimentology of 36 samples was described, and twelve samples were analyzed petrographically. Five lithofacies were characterized: laminated mudstone (Fl), volcaniclastic mudstone (Fv), carbonate (C), evaporite (E), …

Evaluation Of Nocturnal Convective Precipitation Over The Great Plains Using Reanalysis Data And A Wrf-Based Regional Climate Model, Xu Deng

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

This study aims to analyze what processes are mainly responsible for nocturnal convective precipitation during the 1991-2000 period for May-June-July over the Great Plains. Firstly, based on the Weather Research and Forecasting model (WRF) coupled with the NCAR Community Land Model (CLM) and the North American Regional Reanalysis (NARR) reanalysis data, the simulations of the diurnal cycles of LLJ and the convective precipitation are examined. Then, the LLJ-related moisture transport is evaluated since the moisture supply is critical for the development of the heavy rainfall. Results show that the WRF model fails to simulate the nocturnal peak rainfall shown in …