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Post-impact depositional environments as a proxy for crater morphology, Late Devonian Alamo Impact, Nevada

Andrew J. Retzler, Leif Tapanila, Julia R. Steenberg, Carrie J. Johnson and Reed A. Myers
Post-impact depositional environments as a proxy for crater morphology, Late Devonian Alamo Impact, Nevada
Geosphere (Boulder, CO) (January 2015) 11 (1): 123-143

Abstract

Marine facies of carbonate and siliciclastic sediments deposited on top of the upper Devonian Alamo Breccia Member identify the shape and size of the Alamo impact crater in south-central Nevada (western USA). There are 13 measured sections that record peritidal to deep-subtidal deposition across the impacted platform, and these are correlated to three regional depositional sequences above the Alamo Breccia Member. Facies and accommodation patterns identify a concave seafloor that we interpret as the post-impact legacy of the Alamo crater. Together with isopach and lithostratigraphic trends in the underlying Alamo Breccia Member, a new map of the Alamo crater is presented showing the eastern outer rim fault and the annular trough. Size estimates were made using the newly defined crater features and linear scaling relationships from other marine-target complex craters. Revised dimensions of the Alamo crater place its transient diameter between 37 and 65 km, and its apparent diameter between 111 and 150 km. These estimates are more than double previous estimates based on the biostratigraphy of the Alamo Breccia Member. If correct, these new estimates place the Alamo crater as one of the largest marine impacts of the Phanerozoic, and conservatively larger than the well-studied Eocene Chesapeake Bay crater.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 11
Serial Issue: 1
Title: Post-impact depositional environments as a proxy for crater morphology, Late Devonian Alamo Impact, Nevada
Affiliation: Idaho State University, Department of Geosciences, Pocatello, ID, United States
Pages: 123-143
Published: 20150114
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 78
Accession Number: 2015-013838
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. col., 4 tables, geol. sketch map
N36°52'60" - N38°40'00", W115°52'60" - W114°02'60"
Secondary Affiliation: Minnesota Geological Survey, USA, United StatesChesapeake Energy Corporation, USA, United StatesUniversity of Alberta, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201507
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