Physical Sciences and Mathematics Commons^™

The Ages2 (Awards For Geochronology Student Research 2) Program: Supporting Community Geochronology Needs And Interdisciplinary Science, Rebecca M. Flowers, J. Ramón Arrowsmith, Vicki Mcconnell, James R. Metcalf, Tammy M. Rittenour, Blair Schoene

Geosciences Faculty Publications

Geochronology is essential in the geosciences. It is used to resolve the durations and rates of earth processes, as well as test causative relationships among events. Such data are increasingly required to conduct cutting-edge, transformative, earth-science research. The growing need for geochronology is accompanied by strong demand to enhance the ability of labs to meet this pressure and to increase community awareness of how these data are produced and interpreted. For example, a 2015 National Science Foundation (NSF) report on opportunities and challenges for U.S. geochronology research noted: "While there has never been a time when users have had greater …

Evaluating Stable Isotope And Geochronologic Techniques For Paleoclimate Reconstruction: Case Study Of The Santa Cruz Formation, Argentina, Robin B. Trayler

Boise State University Theses and Dissertations

Stable isotope analysis has become the method of choice for many studies investigating the paleoecology and paleoclimate of fossil mammal faunas. While organic tissues (collagen, keratins, proteins) persist for < 10⁵ years highly mineralized tooth enamel is resistant to alteration and degradation and faithfully preserves its isotopic composition for millions (> 10⁶) years. Reconstructing past climates from these records relies on both understanding both micro-scale mechanisms of isotope incorporation into individual teeth, and macro-scale changes in isotope compositions over hundreds of thousands or millions of years. In this dissertation I address three questions.

First, how does the geometry and …

Zircon U-Pb Geochronology Of Two Basement Cores (Kentucky, Usa): Implications For Late Mesoproterozoic Sedimentation And Tectonics In The Eastern Midcontinent, David P. Moecher, J. Richard Bowersox, John B. Hickman

Earth and Environmental Sciences Faculty Publications

Basement cores from two wells drilled west and east of the Grenville front consist of feldspathic litharenite and granitic orthogneiss, respectively. Detrital zircon U-Pb ages for the litharenite define a broad dominant U-Pb age mode at ca. 1115 Ma. The dominant mode matches that for the type locality of the Middle Run Formation in the Ohio subsurface and is interpreted to consist of detrital zircons sourced from East Continent Rift volcanic sources (ca. 1100 Ma) and Grenville Shawinigan granites/gneisses (1120–1180 Ma). The youngest detrital zircon ages (ca. 1020 Ma) require a maximum depositional age that is at least 70 My …

Geochronologic Constraints On The Timing Of Metamorphism And Exhumation Of The Tillotson Peak Complex In Northern Vermont, Cheyne Aiken

Graduate College Dissertations and Theses

The Tillotson Peak Complex (TPC) in northern Vermont records high-pressure (HP) subduction zone metamorphism that occurred during the Ordovician Taconic Orogeny, and subsequent retrograde metamorphism and deformation that occurred during the Silurian Salinic Orogeny. Previous studies have documented a polymetamorphic history, with peak metamorphic pressures possibly up to 2.5 GPa and temperatures of 550°C. Prior to this research, constraints on the timing of metamorphism in the TPC were limited to a single Middle Ordovician 40Ar/39Ar total fusion age for glaucophane. This study integrates 40Ar/39Ar step heating analyses of multiple mineral phases and U-Pb dating of titanite with field and microstructural …