An (U-Th)/He age for the shallow-marine Wetumpka impact structure, Alabama, USA.

Wartho, Jo-Anne , Van Soest, Matthijs C., King, David T. and Petruny, Lucille W. (2012) An (U-Th)/He age for the shallow-marine Wetumpka impact structure, Alabama, USA. Meteoritics & Planetary Science, 47 (8). pp. 1243-1255. DOI 10.1111/j.1945-5100.2012.01381.x.

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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.

Document Type: Article
Keywords: Wetumpka impact structure; Alabama; U-Th/He dating
Refereed: Yes
DOI etc.: 10.1111/j.1945-5100.2012.01381.x
ISSN: 1086-9379
Date Deposited: 18 Nov 2015 13:25
Last Modified: 24 Nov 2015 13:36
URI: http://oceanrep.geomar.de/id/eprint/30232

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