ASU Electronic Theses and Dissertations
- 2 English
It has been hypothesized that the ~25 km Rochechouart-Chassenon impact structure (RCIS) in the NW Massif Central, France, was formed during a Late Triassic (ca. 214 Ma) terrestrial impact event that produced a catena of several large craters. Testing this hypothesis, and assessing its possible impacts on biological evolution, requires both accurate and precise dating of candidate impact structures. Like many of these structures, the age of the RCIS is controversial because geochronological datasets yield contradictory results, even when a single isotopic system is used; for example, the two most recent 40Ar/39Ar studies of RCIS yielded statistically inconsistent dates of …
- Horne, Audrey, Hodges, Kip V., van Soest, Matthijs, et al.
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A mineral’s helium content reflects a balance between two competing processes: accumulation by radioactive decay and temperature-dependent diffusive loss. (U-Th)/He dating of zircon and other uranium and thorium-bearing minerals provides insight into the temperature histories of rocks at or near Earth’s surface that informs geoscientists’ understanding of tectonic and climate-driven exhumation, magmatic activity, and other thermal events. The crystal structure and chemistry of minerals affect helium diffusion kinetics, recorded closure temperatures, and interpretations of (U-Th)/He datasets. I used empirical and experimental methods to investigate helium systematics in two minerals chronometers: zircon and xenotime. The same radioactivity that makes zircon a …
- Anderson, Alyssa Jordan, Hodges, Kip, van Soest, Matthijs, et al.
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