An (U‐Th)/He age for the shallow‐marine Wetumpka impact structure,Alabama, USA |
| |
Authors: | Jo‐Anne WARTHO Matthijs C. VAN SOEST David T. KING JR. Lucille W. PETRUNY |
| |
Affiliation: | 1. School of Earth and Space Exploration, Arizona State University, PO Box 876004, Tempe, Arizona 85287, USA;2. Geology Office, Auburn University, Auburn, Alabama 36849, USA |
| |
Abstract: | Abstract– Single crystal (U‐Th)/He dating was applied to 24 apatite and 23 zircon grains from the Wetumpka impact structure, Alabama, USA. This small approximately 5–7.6 km impact crater was formed in a shallow marine environment, with no known preserved impact melt, thus offering a challenge to common geochronological techniques. A mean (U‐Th)/He apatite and zircon age of 84.4 ± 1.4 Ma (2σ) was obtained, which is within error of the previously estimated Late Cretaceous impact age of approximately 83.5 Ma. In addition, helium diffusion modeling of apatite and zircon grains during fireball/contact, shock metamorphism, and hydrothermal events was undertaken, to show the influence of these individual thermal processes on resetting (U‐Th)/He ages in the Wetumpka samples. This study has shown that the (U‐Th)/He geochronological technique has real potential for dating impact structures, especially smaller and eroded impact structures that lack impact melt lithologies. |
| |
Keywords: | |
|
|