Physical Sciences and Mathematics Commons^™

Trace Element Variations In A Stalagmite From Southwest Mexico: Implications For Paleoclimate, Chad Michael Crotty

UNLV Theses, Dissertations, Professional Papers, and Capstones

The combination of stable isotope and trace element concentrations in speleothems has been shown to be a valuable indicator for interpreting paleoclimatic conditions. Anomalous spikes in trace element concentrations have also been shown to indicate anthropogenic environmental changes to the surface, such as deforestation events. In this study, trace element concentrations (24Mg, 25Mg, 84Sr, 88Sr, 137Ba, and 238U) of a stalagmite (JX-6) from Juxtlahuaca Cave, in southwestern Mexico, were measured using an inductively coupled plasma mass spectrometer (ICP-MS). These trace element concentrations were compared to previously analyzed δ18O and δ13C values from JX-6, and to the results of previous studies …

Modern To Late Pleistocene Stable Isotope Climatology Of Alaska, Alison Sloat

UNLV Theses, Dissertations, Professional Papers, and Capstones

Understanding modern controls on climate is necessary to interpret past climatic conditions. This project investigated the modern controls on δ18O and δD values in Alaskan surface waters to interpret the controls on Late Pleistocene climate variability. ArcGIS was used to develop an isoscape of modern δ18O and δD values of over 400 surface water samples collected across Alaska and the Yukon. It was found that winter temperature and precipitation have the greatest controls on δ18O and δD values in Alaska, resulting in high δ18O values along the coast of the Gulf of Alaska and low values inland toward Central Alaska. …

2000 Year Moisture Source Record From A Central Nevada Speleothem, Paul Pribyl

UNLV Theses, Dissertations, Professional Papers, and Capstones

The goal of this study was to determine the moisture source of winter precipitation in the central Great Basin for the past 2000 years, and to elucidate the role of Pacific Ocean and North American climate variability modes in driving observed droughts of the region around the Medieval Climatic Anomaly (MCA, ~900-1300 CE). Here a high resolution (~2-4 year) precisely dated moisture source reconstruction is presented from the δ18O values of speleothem LC-1 collected from Leviathan Cave in central Nevada, which reveals significant δ18O variability. I attribute the δ18O variability to changes in winter-season moisture circulation over the past 2000 …

Sequence And Chemostratigraphic Study Across The Basal Eureka Quartzite Unconformity In The Great Basin, Nevada: Implications For The Origin Of The Late Ordovician Carbon Isotope Excursion, Apostolos Paul Kosmidis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The positive carbon isotope (δ 13 C) excursion from the late Middle Ordovician Copenhagen Formation that underlies the Eureka Quartzite in central Nevada has been hypothesized to record a global cooling event ∼10 Myr prior to the well-recognized Late Ordovician Hirnantian glaciation (∼443 Ma). However, direct evidence for pre-Hirnantian continental glaciation remains scarce, raising uncertainties in the relationship between the inferred eustatic sea-level fall and the origin of the positive δ 13 C excursion. Additionally, previous stratigraphic studies from southern Nevada and California suggest relative sea-level fall in excess of ∼ 150 meters, which exceeds estimates for younger glacial periods …

Late-Holocene Earthflows Of The Willard Playa/Dune Complex, Estancia Valley, New Mexico: A Geomorphic Response To Climatic Change, Kurt A. Goebel

UNLV Theses, Dissertations, Professional Papers, and Capstones

Late-middle to late Holocene dune sediment that overlies Pleistocene lacustrine sediment marks the onset of xeric conditions in the Estancia Valley, central New Mexico. Incised into the underlying lacustrine sediments, the modern deflation basins are enclosed by parabolic dunes composed of clay and gypsum derived from the underlying sediment.

Located on the in-facing dune slopes of the deflation basins, the most striking geomorphic feature of this dune complex are numerous elongated scars. These relict scars document a geomorphically distinct earthflow event. Arroyos that cut into flow scars expose eolian earthflow sediment overlying lacustrine deposits. In the zone of depletion, erosional-flow …