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Record Details

Record 46 of 1760
Scaling craters in carbonates: Electron paramagnetic resonance analysis of shock damage
External Online Source: doi:10.1029/93JE03574
Author and Affiliation:
Polanskey, Carol A.(California Institute of Technology, Pasadena, California, United States)
Ahrens, Thomas J.(California Institute of Technology, Pasadena, California, United States)
Abstract: Carbonate samples from the 8.9-Mt nuclear (near-surface explosion) crater, OAK, and a terrestrial impact crater, Meteor Crater, were analyzed for shock damage using electron paramagnetic resonance (EPR). Samples from below the OAK apparent crater floor were obtained from six boreholes, as well as ejecta recovered from the crater floor. The degree of shock damage in the carbonate material was assessed by comparing the sample spectra to the spectra of Solenhofen and Kaibab limestone, which had been skocked to known pressures. Analysis of the OAK Crater borehole samples has identified a thin zone of allocthonous highly shocked (10-13 GPa) carbonate material underneath the apparent crater floor. This approx. 5- to 15-m-thick zone occurs at a maximum depth of approx. 125 m below current seafloor at the borehole, sited at the initial position of the OAK explosive, and decreases in depth towards the apparent crater edge. Because this zone of allocthonous shocked rock delineates deformed rock below, and a breccia of mobilized sand and collapse debris above, it appears to outline the transient crater. The transient crater volume inferred in this way is found to by 3.2 +/- 0.2 times 10(exp 6)cu m, which is in good agreement with a volume of 5.3 times 10(exp 6)cu m inferred from gravity scaling of laboratory experiments. A layer of highly shocked material is also found near the surface outside the crater. The latter material could represent a fallout ejecta layer. The ejecta boulders recovered from the present crater floor experienced a range of shock pressures from approx. 0 to 15 GPa with the more heavily shocked samples all occurring between radii of 360 and approx. 600 m. Moreover, the fossil content, lithology and Sr isotopic composition all demonstrate that the initial position of the bulk of the heavily shocked rock ejecta sampled was originally near surface rock at initial depths in the 32 to 45-m depth (below sea level) range. The EPR technique is also sensitive to prehistoric shock damage. This is demonstrated by our study of shocked Kaibab limestone from the 49,000-year-old Meteor (Barringer) Crater Arizona.
Publication Date: Mar 25, 1994
Document ID:
(Acquired Dec 28, 1995)
Accession Number: 95A85876
Document Type: Journal Article
Publication Information: Journal of Geophysical Research (ISSN 0148-0227); 99; E3; p. 5,621-5,638
Publisher Information: United States
Financial Sponsor: NASA; United States
Organization Source: NASA; Washington, DC, United States
Description: 18p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
Imprint And Other Notes: Journal of Geophysical Research vol. 99, no. E3 p. 5,621-5,638 March 25, 1994
Miscellaneous Notes: Research supported by NASA
Availability Source: Other Sources
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