Site report for USGS test holes drilled at Cape Charles, Northampton County, Virginia, in 2004

By Gregory S. Gohn, Ward E. Sanford, David S. Powars, J. Wright Horton, Jr., Lucy E. Edwards, Roger H. Morin, and Jean M. Self–Trail

PDF (2,761KB, 27 pages)

Abstract

The U.S. Geological Survey drilled two test holes near Cape Charles, Virginia, during May and June 2004, as part of an investigation of the buried, late Eocene Chesapeake Bay impact structure. The first hole is designated as the USGS–Sustainable Technology Park test hole #1 (USGS–STP1). This test hole was abandoned at a depth of 300 ft; cuttings samples were collected, but no cores or geophysical logs were acquired. The second hole is designated as the USGS–Sustainable Technology Park test hole #2 (USGS–STP2). This test hole was drilled to a depth of 2,699 ft. Cores were collected between depths of 1,401.7 ft and 1,420.7 ft and between 2,440.0 ft and 2,699.0 ft. Cuttings samples were collected from the uncored intervals below 280–ft depth. Interim sets of geophysical logs were acquired during the drilling operation, and one final set was acquired at the end of drilling. Two wells were installed in the USGS–STP2 test hole. The deep well (designated 62G–24) was screened between 2,260 ft and 2,280 ft, and the shallow well (designated 62G–25) was screened between 1,360 ft and 1,380 ft. Ground–water salinities stabilized at 40 parts per thousand for the deep well and 20 parts per thousand for the shallow well. The geologic section encountered in the test holes consists of three main units: (1) Eocene, Oligocene, Miocene, Pliocene, and Pleistocene sands and clays are present between land surface and a depth of 1,163 ft; (2) sediment–clast breccias of the impact structure are present between depths of 1,163 ft and 2,150 ft; and (3) crystalline–clast breccias and cataclastic gneiss of the impact structure are present between depths of 2,150 ft and 2,699 ft.

Contents

• Figures
• Tables
• Conversion Factors
• Abstract
• Introduction
• Background
• Drill Site
• Drilling Operations
  • Drilling Equipment
  • Drilling and Logging History
  • Drilling Rate
  • Coring Runs
  • Geophysical Logging
  • Well Installation
• Preliminary Site Geology
  • Crystalline–clast Breccia and Cataclastic Gneiss
  • Sediment–Clast Breccia
  • Postimpact Sediments
    • Upper Eocene Section – Chickahominy Formation (1,163 ft to 993 ft)
    • Oligocene Section – Delmarva Beds, Drummonds Corner Beds, Old Church Formation (993 to 955 ft)
    • Lower and Middle Miocene Section – Calvert and Choptank Formations (955 ft to 606 ft)
    • Upper Miocene Section – St. Marys and Eastover Formations (606 ft to 168 ft)
    • Pliocene Section – Yorktown and Chowan River Formations (168 ft to 32 ft)
    • Pleistocene Section – Nassawadox Formation (32 ft to 5 ft)
    • Modern Artificial Fill (5 ft to 0 ft)
• Acknowledgments.
• References Cited
• Appendix A: Drill–Site Staff
• Drillers
• Site Geologists and Biologists
• Geophysical Loggers

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