The ICDP-USGS Deep Drilling Project in the Chesapeake Bay impact structure: Results from the Eyreville Core Holes
Paleoenvironmental recovery from the Chesapeake Bay bolide impact: The benthic foraminiferal record
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Published:January 01, 2009
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CiteCitation
C. Wylie Poag, 2009. "Paleoenvironmental recovery from the Chesapeake Bay bolide impact: The benthic foraminiferal record", The ICDP-USGS Deep Drilling Project in the Chesapeake Bay impact structure: Results from the Eyreville Core Holes, Gregory S. Gohn, Christian Koeberl, Kenneth G. Miller, Wolf Uwe Reimold
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The late Eocene Chesapeake Bay bolide impact transformed its offshore target site from an outer neritic, midshelf seafloor into a bathyal crater basin. To obtain a depositional record from one of the deepest parts of this basin, the U.S. Geological Survey (USGS) and the International Continental Scientific Drilling Program (ICDP) drilled a 1.76-km-deep core hole near Eyreville, Virginia. The Eyreville core and eight previously cored boreholes contain a rarely obtainable record of marine deposition and microfossil assemblages that characterize the transition from synimpact to postimpact paleoenvironments inside and near a submarine impact crater. I used depositional style and benthic foraminiferal assemblages to recognize a four-step transitional succession, with emphasis on the Eyreville core. Step 1 is represented by small-scale, silt-rich turbidites, devoid of indigenous microfossils, which lie directly above the crater-filling Exmore breccia. Step 2 is represented by very thin, parallel, silt and clay laminae, which accumulated on a relatively tranquil and stagnant seafloor. This stagnation created a dead zone, which excluded seafloor biota, and it lasted ~3–5 ka. Step 3 is an interval of marine clay deposition, accompanied by a burst of microfaunal activity, as a species-rich pioneer community of benthic foraminifera repopulated the impact site. The presence of a diagnostic suite of agglutinated foraminifera during step 3 indicates that paleoenvironmental stress related to the impact lasted from ~9 ka to 400 ka at different locations inside the crater. During step 4, the agglutinated assemblage disappeared, and an equilibrium foraminiferal community developed that contained nearly 100% calcareous species. In contrast to intracrater localities, core sites outside and near the crater rim show neither evidence of the agglutinated assemblage, nor other indications of long-term biotic disruption from the bolide impact.
- assemblages
- benthic taxa
- Cenozoic
- Chesapeake Bay impact structure
- Chicxulub Crater
- communities
- cores
- Eocene
- faunal list
- Foraminifera
- impacts
- International Continental Scientific Drilling Program
- Invertebrata
- lithostratigraphy
- marine environment
- microfossils
- morphology
- Northampton County Virginia
- paleoecology
- paleoenvironment
- Paleogene
- Protista
- SEM data
- shelf environment
- Tertiary
- United States
- upper Eocene
- Virginia
- Eyreville Farm