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Investigating pressure magnitudes at depth for oblique impacts into layered targets: Applications to terrestrial impacts in sedimentary targets
Author(s) -
Stickle A. M.,
Schultz P. H.
Publication year - 2013
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12152
Subject(s) - geology , impact crater , impact structure , dome (geology) , shock (circulatory) , bedrock , sedimentary rock , deformation (meteorology) , geologic record , quartz , petrology , seismology , geomorphology , geochemistry , paleontology , medicine , oceanography , physics , astronomy
The positive identification of the Rock Elm impact structure (Wisconsin, USA ) and the Upheaval Dome (Utah, USA ) as impact craters was complicated by a lack of distinctive shock features in the record. Low‐impedance surface layers over high‐impedance bedrock affect energy coupling and shock effects in the substrate; in both cases, removal of surface sediments erased most of the original impact structures, thereby making identification of the impact origin difficult. In this study, a combination of laboratory and 3‐D numerical experiments reveals the underlying processes controlling subsurface deformation and demonstrates that a low‐impedance layer can reduce expression of peak shock pressures left in the rock record, as at the Rock Elm and the Upheaval Dome impact sites. 3‐D CTH models of the Rock Elm impact structure predict that peak shock pressures should fall below the hugoniot elastic limit of quartz in the basement rocks, yet still induce permanent deformation. The model predicts peak pressures around 5–10 GPa, levels consistent with field observations of shocked quartz from both Rock Elm and the Upheaval Dome. Consequently, other impact sites exhibiting minimal shock features might be explained.