Identifying Fossil Shell Resources via Geophysical Surveys: Chesapeake Bay Region, Virginia

Methodology capable of identifying fossil oyster shell (FOS) buried under several meters of sediment is needed to quantitatively assess the availability of FOS for oyster reef restoration in Virginia. Evaluated here is the feasibility of using acoustic sub-bottom seismic surveys for determining the location and quantity of buried FOS. Over 280 miles of seismic surveys and 117 cores were collected in seven regions of the Chesapeake Bay and its tributaries. Traditional methods of seismic interpretation were able to successfully identify buried FOS regions throughout the geologically complex study area. The acoustic nature of buried FOS is site specific, however, and requires groundtruthing and geologic expertise to identify in the seismic data. Buried FOS deposits range in thickness from 1 to 3 ft, are located 2 to 8 ft below the seafloor, and are comprised of 12% to 55% shell. Overall, the seven sites contain a minimum of 877,300 ft3 of buried FOS sediment, of which a minimum of 288,000 ft3 is shell material. Although a purely quantitative assessment of acoustic data is possible, it is empirical and must be tuned from site to site. Ultimately, it is recommended that a combination of geologic digitizing and quantitative assessment be used to identify buried FOS regions in future seismic studies.