Chesapeake Impact Crater Fault Line Location Project Part 2
Purpose of study: Geologic mapping outside of NPS boundaries has recently located one or more faults. These faults are projected into COLO park. We would like to provide the Park with updated geologic information for their resource management and complete the geologic mapping of the Williamsburg 30- by 60-minute quadrangle by mapping these features through the Park. These faults are not geologically active, but the result of the impact that created the Chesapeake Bay.
Summary of field methods and activities: The faults are likely not exposed at ground surface due to vegetation, colluvium and alluvium and Pleistocene deposits. The samples will be taken with an auger drill mounted on a F350 pickup. 4-inch diameter borings will be drilled in several places that have been cleared and approved by Park staff. The borings will identify geologic formations below ground and document the elevation of contacts between the formations. This drilling will show where abrupt changes in laterial continuity of the contacts occur, and therefore show where faulting has occurred. Typical boring depth ranges from 50 to 60 feet, but local conditions may require drilling to 100 feet. After drilling, the sediments will be placed back into the hole and compacted. A plastic plug will be inserted at a depth of 4 feet, clayey sediments will be packed into the remaining top 4 feet. Extra sediment will be scattered into adjacent woods and the drill site will be raked and cleaned up. After a few rainstorms, evidence of our having worked at the site will be gone.
Natural Resource Specialist
Colonial National Historical Park
Rick Berquist, a geologist with the State of Virginia, has applied for a research permit with the Park to continue his research on the geologic faults associated with the Chesapeake Bay Impact Crater. Mr. Berquist previously searched for the fault to the east of the current project area without success and has asked the Park to expand his study area to the west and to extend the expiration of his research permit.