
Paleoenvironmental recovery from the Chesapeake Bay bolide impact: The benthic foraminiferal record
Special Paper of the Geological Society of America
- By:
- C.W. Poag
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Abstract
The late Eocene Chesapeake Bay bolide impact transformed its offshore target site from an outer neritic, midshelf seafl oor 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 Scientifi c 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-fi lling Exmore breccia. Step 2 is represented by very thin, parallel, silt and clay laminae, which accumulated on a relatively tranquil and stagnant seafl oor. This stagnation created a dead zone, which excluded seafl oor 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.
Additional publication details
- Publication type:
- Article
- Publication Subtype:
- Journal Article
- Title:
- Paleoenvironmental recovery from the Chesapeake Bay bolide impact: The benthic foraminiferal record
- Series title:
- Special Paper of the Geological Society of America
- DOI:
- 10.1130/2009.2458(32)
- Issue:
- 458
- Year Published:
- 2009
- Language:
- English
- Publisher:
- Geological Society of America
- Contributing office(s):
- Woods Hole Coastal and Marine Science Center
- Description:
- 27 p.
- First page:
- 747
- Last page:
- 773
- Country:
- United States
- Other Geospatial:
- Chesapeake Bay