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

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 seafl oor 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 defi ned crater features and linear scaling relationships from other marinetarget 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 wellstudied Eocene Chesapeake Bay crater.

The Sedimentary records of the Hapcheon impact crater basin in Korea over the past 1.3 Ma

“…Some global examples of meteorite impact craters are lakes undergoing active sedimentation (Fredriksson et al, 1973;Guyard et al, 2011;Melles et al, 2011;Shanahan et al, 2012;Reimold and Koeberl, 2014;Losiak et al, 2016;Lim et al, 2021). Meteorite impact craters have been reported worldwide, including in the oceans (Jones et al, 1981;Reimold et al, 1998;Gurov et al, 2007;Liu et al, 2013;Reimold and Koeberl, 2014;Retzler et al, 2015;Ebinghaus et al, 2017;McLean et al, 2018). The Hapcheon meteorite impact crater currently has a small basin shape, containing >100 m of sediment, and a >72 m thick sediment layer has been reported in the lake (Lim et al, 2021).…”