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Ecosystem perturbation caused by a small Late Cretaceous marine impact, Gulf Coastal Plain, USA

By
David T. King, Jr.
David T. King, Jr.
Department of Geology, Auburn University, Auburn, Alabama 36849-5305, USA
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Lucille W. Petruny
Lucille W. Petruny
Astra-Terra Research, Auburn, Alabama 36831-3323, USA
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Thornton L. Neathery
Thornton L. Neathery
Neathery and Associates, 1212-H Veterans Parkway, Tuscaloosa, Alabama 35404, USA
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Published:
January 01, 2007

The Wetumpka impact event, ca. 83.5 Ma in shallow waters of the northern Gulf of Mexico, caused minor ecosystem perturbations because of the physical effects of a 2.6-gigaton-equivalent impact detonation. The impact event and its consequences had relatively minor, but notable, paleobiologic effects (i.e., preservational effects, biostratigraphic effects, and impact-succession effects). The impact structure served as a local reservoir for an impact-entombed fossil record in two main ways. First, coarse to fine fragments of terrestrial vegetation, probably derived from the adjacent tropical forest, were swept up and incorporated into Wetumpka washback- and surgeback-deposited breccias and sands. Second, intact blocks of target sedimentary units, which contain an internal fossil component of their own, are part of the slump and fallback debris that partially fills the Wetumpka impact structure. Some of these target sedimentary rock blocks include updip sedimentary facies of these formations that no longer exist in outcrops anywhere in the region. In yet another paleoecologic effect, the Wetumpka impact crater apparently functioned as a minor terrestrial (island) ecosystem embedded within the shelfal marine realm for an unknown length of time. As one might expect from the relatively small size of this structure, there is no apparent regional or global biotic extinction event associated with this local catastrophe.

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Contents

GSA Special Papers

Large Ecosystem Perturbations: Causes and Consequences

Simonetta Monechi
Simonetta Monechi
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Rodolfo Coccioni
Rodolfo Coccioni
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Michael Rampino
Michael Rampino
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Geological Society of America
Volume
424
ISBN print:
9780813724249
Publication date:
January 01, 2007

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