Document Type

Thesis

Abstract

The purpose of this study is to assess the effects of the Chesapeake Bay impact on calcareous nannofossils during the Late Eocene. The Chesapeake Bay impact occurred 35 million years ago (Ma), when an asteroid or comet fragment struck the Chesapeake Bay and excavated a crater approximately 90km in diameter. To examine the structure of the crater, continuous sediment core holes have been drilled and recovered in southeastern Virginia and the Delmarva Peninsula. This study focuses on two U.S. Geological Survey continuous core holes: the Watkins Core from Newport News, VA, and the North Core from North, VA. Although the nannofossil assemblages from previous cores have been described, the nannofossil records from these two cores have yet to be examined. This research involves a detailed stratigraphic assessment of the calcareous nannofossil assemblages from the Late Eocene post-impact Chickahominy Formation in order to determine whether the impact produced a local extinction, and if so, whether this extinction was followed by a recovery interval. Preliminary results suggest that, despite its size, the Chesapeake Bay impact did not significantly affect the local calcareous nannoplankton community. This is supported by the lack of preservational change and the only slight change recorded in either species composition or diversity across the impact boundary in the Watkins Core. These findings also do not support the existence of a calcareous nannofossil “dead zone” following the impact boundary in the Watkins Core. The presence of impact-fractured nannofossils and coccospheres were also documented, and may attest to the pressures generated by the impact and possibly the poor environmental conditions that resulted from the impact respectively.

Date Awarded

2003

Department

Geology

Advisor 1

Rowan Lockwood

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