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TitleThe subsurface character of meteor crater, Arizona, as determined by ground - probing radar
AuthorPilon, J A; Grieve, R A F; Sharpton, V L
SourceJournal of Geophysical Research vol. 96, no. E1, 1991 p. 15563-15576,
Alt SeriesGeological Survey of Canada, Contribution Series 21890
Mediapaper; on-line; digital
File formatpdf
AreaCanyon Diablo Area; Arizona; United States of America
Lat/Long WENS-111.0333 -111.0000 35.0500 35.0167
Subjectsstratigraphy; extraterrestrial geology; geophysics; structural geology; meteorite craters; structural features; ground probing radar; geophysical surveys; water table; faults; Colorado Plateau; Moenkopi Formation; Kaibab Formation
Illustrationstables; photographs; cross-sections; radar profiles
Released2012 09 21
AbstractGround-probing radar has provided new two-dimensional stratigraphic and structural information on Meteor Crater, Arizona. Four 50-MHz transects inside the crater and one 100-MHz transect on a northeast radial across the exterior ejecta blanket were carried out. The frequencies used were in relation to the desired depth of investigation: greater than 50 m at 50 MHz and ~30 m for 100 MHz. The results obtained inside the crater show that the water table can be clearly detected at depths of ~65 m, as can the contact between the crater wall and the infilling allochthonous breccia lens. In addition, we were able to detect (1) point reflectors from relatively coherent blocks (>1.5m) within the breccia lens, (2) a zone ~7 m thick relatively free of point reflectors from the immediate fall back unit, (3) a series of subhorizontal reflectors a few meters apart due to bedding in the post impact crater sediments, and (4) five separate subhorizontal reflectors from what we interpret to be a series of postimpact paleo-water table levels in the breccia lens. The ejecta blanket transect indicates a ~4–10 m thick ejecta layer and the underlying Moenkopi Formation sandstone, as well as the Moenkopi-Kaibab contact and bedding within the Kaibab Formation. In addition, reverse faults with displacements up to 4 m were detected in the bedrock, as well as changes from subhorizontal to ~30° in the dip of the bedrock as the crater rim is approached from the northeast. Beneath the ejecta blanket, the total uplift observed at the crater rim is around 55 m. The radar data indicate uplift effects out to a radial distance of ~400 m from the rim, farther than that determined from drilling (~300 m). The results demonstrate the utility of continuous ground-probing radar cross sections in studying the near-subsurface (~50 m) character at Meteor Crater. This relatively rapid, low cost technique can be extended to other structures, but confident interpretation requires supplemental ground truth constraints.

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