Physical Sciences and Mathematics Commons^™

A Niobium Deposit Hosted By A Magnetite-Dolomite Carbonatite, Elk Creek Carbonatite Complex, Nebraska, Usa, Michael J. Blessington

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

The Elk Creek Carbonatite Complex (ECCC) is a large Early Cambrian carbonatite complex that intrudes Precambrian basement rocks in Southeast Nebraska. This dolomitic carbonatite complex includes a magnetite-dolomite rock with accessory barite, ilmenite, rutile, and quartz. This rock is identified by a characteristic enrichment in niobium due to accessory pyrochlore mineralization in the form of disseminations and inclusions in ilmenite and magnetite. Pyrochlore is also present in other carbonatite rocks in the complex as an accessory mineral with sporadic local high-grade intercepts in drill cores.

Carbonatite rock samples are characterized by transmitted-light microscopy, cathodoluminescent microscopy, backscattered electron imaging (BEI), and …

Identification Of Groundwater Sources For Municipal Wells Using Geochemical Data On The Platte Alluvial Aquifer And Underlying Limestone At The Lincoln Water Well Field Near Ashland Nebraska, Juanita Cruz Torres

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

Alluvial aquifer systems where pumping of municipal wells induces recharge from the adjacent river are the primary source of water for many cities. The city of Lincoln, NE has a primary water source in an alluvial aquifer adjacent to the Platte River. The Lincoln Water System manages the stream/aquifer system by using integrated models for a better understanding during periods of high stress such as a drought. The integrated models set the limestone aquifer as an impermeable boundary to understand the alluvial aquifer system without having a secondary water source. The limestone aquifer is permeable and the purpose of this …

Cloud Impacts On Pavement Temperature And Shortwave Radiation, Curtis L. Walker

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

Forecast systems provide decision support for end-users ranging from the solar energy industry to municipalities concerned with road safety. Pavement temperature is an important variable when considering vehicle response to various weather conditions. A complex, yet direct relationship exists between tire and pavement temperatures. Literature has shown that as tire temperature increases, friction decreases which affects vehicle performance. Many forecast systems suffer from inaccurate radiation forecasts resulting in part from the inability to model different types of clouds and their influence on radiation. This research focuses on forecast improvement by determining how cloud type impacts pavement temperature and the amount …

Verification And Analysis Of Impact-Based Tornado Warnings In The Central Region Of The National Weather Service, Holly B. Obermeier

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

Tornado warnings are one of the most critical products issued by the National Weather Service (NWS), and favorable verification statistics are desirable. The 2011 NWS statistics for traditional tornado warnings indicate that the probability of detection (POD) is 70%, while the false alarm rate (FAR) is 76%. The recent Joplin, Missouri EF5 tornado event on 22 May 2011, which resulted in massive devastation and loss of life, prompted the NWS to re-evaluate the current tornado warning format. After the Joplin, MO event, the Central Region of the NWS implemented the impact-based tornado warning (IBTW) experiment in 2013. IBTWs consist of …

Eastern Us Dryline Climatology And Synoptic-Scale Environment, Rebecca S. Duell

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

The dryline is an important focal point for convection initiation, and the subject of many studies. While the most common location for drylines is the southern Great Plains, dryline passages and subsequent severe weather outbreaks have been documented in the Mississippi River Valley and into portions of the southeastern United States. Little is known about these “eastern” drylines or how often they occur, as no climatologies or detailed studies have been published on them. This thesis presents a fifteen-year climatology (1999-2013) of eastern drylines in an effort to identify how often and where they typically occur, and to identify synoptic …

Aerosol Association With Severe Weather In The Great Plains, Gabriel A. Lojero

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

Aerosols particles may serve as cloud condensation nuclei (CCN) and therefore play an important role in modulating cloud microphysics, to the point where convective storm intensity may be altered. The purpose of this study is to determine the impacts of biomass burning aerosols on convective storms over the Great Plains, especially the southern Great Plains, and to show synoptic regimes characterizing differing aerosol concentrations. A new technique to identify days with a high concentration of biomass burning aerosols was developed by using organic carbon, potassium, zinc, and bromine as the predominant tracers. An eleven-year climatology (2002-2012) for the biomass burning …

Springtime Atmospheric Responses To North Atlantic Sst Anomalies In Idealized Gcm Experiments: Northern Hemisphere Circulation And North American Precipitation, Michael C. Veres

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

In this study, a series of experiments using idealized sea surface temperatures (SST), land and orography are performed to examine the interactions between the Atlantic Multidecadal Oscillation (AMO), continents and major orography. Three sets of experiments are done using an increasingly realistic surface boundary (aqua-planet, land without orography and land with orography) and run using perpetual equinox conditions. For each land surface boundary, the model is forced with a zonally symmetric SST, with additional experiments with an imposed positive or negative SST anomalies in the North Atlantic. The experiments are then compared to determine how these forcings interact and what …

Sedimentological And Stratigraphic Study Of A Falling-Stage Delta Complex In The Upper Cretaceous (Turonian) Ferron Sandstone Member Of The Mancos Shale, South-Central Utah, Usa, Fares Alaboud

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

The character and distribution of lithofacies in falling-stage deltas are incompletely documented. This paper presents a sedimentological and stratigraphic evaluation of a superbly-exposed interval of Cretaceous deltaic strata that are believed to be of falling stage origin. The studied interval forms part of the Upper Cretaceous (Turonian) Ferron Sandstone Member of the Mancos Shale in the southernmost Henry Mountains Basin of south-central Utah, USA. The interval of interest is exposed in three dimensions over a 20 km² area in a series of canyon walls. Observed facies include fine-grained mudrocks (offshore basin), mudrocks with thinly interlaminated sandstone (prodelta), thinly interbedded …

Watershed And Aquatic Ecosystem Evolution During The Late-Glacial And Early-Holocene Inferred From High-Resolution Diatom And Geochemical Records In The Yellowstone Region, Yanbin Lu

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

High-resolution diatom records spanning the late-glacial and early-Holocene were developed from three lakes in the Yellowstone region to infer the lake history and to evaluate the relative importance of climatic versus non-climatic factors on the aquatic ecosystem evolution. Synchronous shifts in diatom community structure occurred in all lakes, which are located in regions of varied surficial geology and precipitation seasonality, in the intervals of 13.9-13.8, 13.2-13.1, 11.3-11.0 and 8.8-8.7 cal ka. The synchronous diatom community structure shifts suggest that large-scale climatic change is the primary driver of the aquatic ecosystem evolution in this region, whereas the influence of non-climatic factors …

Origin And Distribution Of The Mississippian – Pennsylvanian Boundary Unconformity In Marine Carbonate Successions With A Case Study Of The Karst Development Atop The Madison Formation In The Bighorn Basin, Wyoming., Lucien Nana Yobo

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

The causal mechanism of the widespread unconformity that encompasses the Mississippian – Pennsylvanian boundary remains poorly understood. This unconformity, first thought to be restricted to North America, is now known to be present in other regions of the globe. Possible causes for the unconformity include (1) sea level draw down from the onset of glaciation at start of the late Paleozoic ice age and (2) increased tectonic activity from the formation of the supercontinent of Pangea. Thus the origin of the unconformity is still poorly constrained.

This study examines possible causal mechanisms for the widespread unconformity that encompasses the Mississippian …

Pore Water Extraction For Unsaturated Zone Isotope Research: An Investigation Using An Immiscible Displacement Fluid And A Centrifuge, Caitlin Burnett Weaver

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

Accurate and reliable pore water extraction techniques are important to an array of scientific fields including, but not limited to, hydrogeology, soil science, and paleoenvironmental research. The aim of the current project is to test the applicability of an immiscible displacement extraction technique for stable isotopes of water under a range of textural, hydrologic, and chemical conditions. In this study, laboratory experiments were conducted to establish the extent to which the proposed method 1) achieves sufficient yield for laboratory isotopic analyses, 2) results in isotopic exchange between water and the displacement fluid, 3) conserves initial isotopic compositions of spike test …

Assessing Layer Parallel Shortening In The Eastern Colorado Front Range Using Thin Section Analysis And Analog Sandbox Models, Nicole Pierson

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

Layer parallel shortening (LPS) is an expression of compressive strain that occurs parallel to bedding surfaces. LPS is chiefly expressed by chemical changes to sediment volume, including stylolitization, porosity reduction and impingement of grains. This strain is typically omitted in the process of cross-section restoration due to a lack of understanding of spatial and temporal LPS accommodation. Bulk shortening calculated is considered to be a minimum shortening estimate. However, dismissing this inaccuracy due to shortening can lead to significant error in subsurface predictions and reconstructions.

To address this problem, a combination of thin section analysis and analog modeling assessed the …

Early And Late Iron Diagensis In The Upper Triassic Shinarump Member Of The Chinle Formation (Utah And Arizona), Derek T. Burgess

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

The fluvial Shinarump Member of the Chinle Formation in southwestern Utah and northwestern Arizona contains several distinct types of diagenetic iron accumulations. They range to more than 50 cm in diameter, and are dominantly composed of iron-oxide cement, but siderite, rhodochrosite and pyrite cements are common. Iron-oxide cements occur in all facies, but are most abundant in channel sandstone bodies. There, iron-oxide-cement occurs as wonderstone fabric (rinds & staining), dispersed rhombic pseudomorphs, and as discoidal concretions within intraformational conglomerates. Evidence from Shinarump sediment indicates that the ferrous carbonate mineral siderite (FeCO₃) was the precursor mineral for current iron-oxide …

Fossil Crocodilians From The High Guajira Peninsula Of Colombia, And The History Of Neogene Crocodilian Diversity In Tropical South America, Jorge W. Moreno-Bernal

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

The greatest diversity of Cenozoic crocodilians occurred during the Miocene in equatorial South America. However, the origin of this high diversity and its relationship to environmental factors are poorly understood. Most described species come from localities assigned to Laventan (13.8-11.8 Ma) and Huayquerian (9.0-6.8 Ma) South American land mammal ages (SALMAS), whereas the record is sparse in the early to middle Miocene and after the latest Miocene and Pliocene. Field research in the Castilletes (early Miocene-Pliocene) Formation in the High Guajira Peninsula of Colombia provides new fossil data on the origin of Neotropical crocodylian diversity. The Castilletes Formation crops out …

Body Size And Species Richness Changes In Glyptosaurinae (Squamata: Anguidae) Through Climatic Transitions Of The North American Cenozoic, Sara Elshafie

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

Poikilothermic vertebrates offer excellent climate proxies based on relationships between environment and measurable variables such as body size and species richness. Relationships of these variables in lizards to environmental transitions over long time scales are poorly understood. Here I show that patterns of body size and species richness in a lizard clade, Glyptosaurinae (Squamata: Anguidae), correspond to known histories of paleotemperatures through the Cenozoic of North America. Glyptosaurines have the richest fossil record among North American Cenozoic lizards and exhibit a wide range of skull sizes. In order to estimate body size for glyptosaurines and other fossil anguids, I collected …