Late Eocene impacts: Geologic record, correlation, and paleoenvironmental consequences

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Abstract

We present new magnetostratigraphic and stable isotopic (๐œน18C, ๐œน13Ccarb) data to help improve correlations among three late Eocene impact craters and their inferred breccia and ejecta deposits. Our analyses also shed light on potential global environmental consequences attributable to the impacts. The new data come from a continuously cored interval of the subsurface Chickahominy Formation, which lies conformably above the Chesapeake Bay impact crater in southeastern Virginia. The new magnetostratigraphic data indicate that the Chesapeake Bay impact took place in Chron C16n. 2n, the same magnetochron that encompasses the late Eocene ejecta layer at Massignano, Italy. This correlation places both the Chesapeake Bay impact and the Massignano ejecta at ~35.6 Ma, and resolves a previous miscorrelation between these two sites based on planktonic foraminifera and calcareous nannofossils. The new magnetostratigraphic correlations also suggest that the published magnetostratigraphic framework for ejecta-bearing late Eocene strata ar ODP Site 689B (Maud Rise) is incorrect, due to an incomplete section.

New ๐œน18C data (single species of benthic foraminifera) from the same Chickahominy section ar Chesapeake Bay indicate that successional intervals of warm oceanic bottom-water may be characteristic of the late Eocene. We infer that the warm intervals correlate with successive episodes of greenhouse warming, triggered in part by a comer shower, which produced the Chesapeake Bay, Toms Canyon, Popigai, and presumably additional (as yet undiscovered) late Eocene impact craters. 

We also demonstrate that a marked negative execution of ๐œน13Ccarb persists through the upper half of the Chickahominy Formation. This excursion, also recorded at Massigno, at Bath Cliff, Barbados, and at other widespread localities in the world ocean, may be additional evidence of global-scale, long-term environmental disturbances related to the bolide impacts. As such, this  ๐œน13C signal may be useful for global subdivision of the late Eocene stratigraphic record.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Late Eocene impacts: Geologic record, correlation, and paleoenvironmental consequences
ISBN 9780231127165
Year Published 2003
Language English
Publisher Columbia University Press
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 16 p.
Larger Work Title From Greenhouse to Icehouse
First page 495
Last page 510