Search for a meteoritic component in impact breccia from the Eyreville core, Chesapeake Bay impact structure: Considerations from platinum-group element contents.

Iain McDonald, Katerina Bartosova, Christian Köberl

Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

Abstract

This paper documents an attempt to detect a meteoritic component in both wash-back (resurge) crater-fill breccia (the so-called Exmore breccia) and in suevites from the Eyreville core hole, which was drilled several kilometers from the center of the 85-km-diameter Chesapeake Bay impact structure, Virginia, USA. Determining the presence of an extraterrestrial component and, in particular, the projectile type for this structure, which is the largest impact structure currently known in the United States, is of importance because it marks one of several large impact events in the late Eocene, during which time the presence of extraterrestrial 3He and multiple impact ejecta layers provide evidence for a comet or asteroid shower. Previous work has indicated an ordinary chondritic projectile for the largest of the late Eocene craters, the Popigai impact structure in Siberia. The exact relation between the Chesapeake Bay impact event and siderophile element anomalies documented in late Eocene ejecta layers from around the world is not clear. The only clear indication for an extraterrestrial component related to this structure has been the discovery of a meteoritic osmium isotopic signature in impact melt rocks recovered from a hydrogeologic test hole located on Cape Charles near the center of the structure, and confirmation of a similar signature in suevitic rocks would have been desirable in order to place constraints on the type of projectile involved in formation of the Chesapeake Bay crater. Unfortunately, the current data show no discernible differences in the contents of the platinum group elements (PGEs) among the suevite, the Exmore breccia, and several crystalline basement rocks, all from the Eyreville core hole. Abundances of PGEs are uniformly low (e.g.,
OriginalspracheEnglisch
Seiten (von - bis)469-479
Seitenumfang11
FachzeitschriftGeological Society of America. Special Papers
Jahrgang458
DOIs
PublikationsstatusVeröffentlicht - 2009

ÖFOS 2012

  • 105101 Allgemeine Geologie

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