Geophysical Signature of the Chesapeake Bay Impact Crater (Late Eocene)

Details Geophysical Signature of the Chesapeake Bay Impact Crater (Late Eocene) Geophysical Signature of the Chesapeake Bay Impact Crater (Late Eocene)

Sep 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995metic..30s.561p&link_type=abstract

Meteoritics, vol. 30, no. 5, page 561

Physics

Crater, Bouguer Gravity Anomaly, Chesapeake Bay, Geophysical Signature, Structure, Impact Crater

Scientific paper

The Chesapeake Bay impact crater is defined on the basis of (1) seismic-reflection profiles that cross lower Chesapeake Bay and the continental shelf east of the Delmarva Peninsula; (2) Bouguer and free-air gravity measurements from the bay, the surrounding peninsulas, and the continental shelf; (3) two continuous core holes drilled inside the crater, and two drilled outside the crater [1]. Seismic profiles reveal a roughly skillet shaped (flat-floored) crater, 90 km in diameter, buried beneath 400-500 m of postimpact sedimentary strata. Concentric, down-faulted terraces of the crater's outer rim form a 350-m-high escarpment bounding the annular trough. The annular trough, floored by block-faulted Lower Cretaceous sedimentary rocks, is separated from the inner basin by a 150-200-m-high crystalline peak ring. The inner basin, which is 30 km in diameter and 800-1,000 m deep, is excavated into crystalline basement rocks of the Appalachian orogen. A circular, negative, 28-mGal Bouguer gravity anomaly is present directly over the seismically defined inner basin. The presence of a central peak may be indicated, however, by several relative gravity highs near the center of the negative anomaly. As one traces the impact-generated Exmore breccia across the crater's outer rim into the annular trough, the deposit characteristically thickens by a factor of 10, and its upper surface exhibits a notable structural sag. References: [1] Poag C. W. et al. (1994) Geology, 22, 691-694.

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