MARINE MINERAL RESOURCES ON VIRGINIA’S OUTER CONTINENTAL SHELF: QUANTIFYING SAND DEPOSITS FOR COASTAL RESTORATION AND OCCURRENCES OF ECONOMIC HEAVY MINERALS

Shoreline protection is vital to the regional economies of popular tourist destinations in Virginia including Chincoteague Island and Virginia Beach. Since the late 1940s, sand from inland borrow sites, channel dredge spoils and offshore deposits has been transported to these areas to help protect and restore the coastline. Beach replenishment projects have also aided in the protection of national infrastructure at NASA’s Wallops Flight Facility and at Naval Station Oceana Dam Neck Annex. Increasing constraints on the availability of on-shore and near-shore beach-quality sand resources have placed new emphasis on identifying resources on the outer continental shelf (OCS).

Following the coastal impacts of Hurricane Sandy in 2012, the U.S. Bureau of Ocean Energy Management (BOEM) partnered with the Virginia Department of Mines, Minerals and Energy (DMME) to investigate new sources of sand for beach replenishment projects, and to also identify and quantify economic minerals on the OCS. New data collected for BOEM within 3 to 8 nautical miles offshore of the Delmarva Peninsula and Sandbridge included high-resolution chirp sub-bottom profiles, side scan sonar, multi-beam bathymetry and sediment cores. Interpretation of the reconnaissance-level data has enabled mapping of Holocene-age sand shoals, sheets, and paleo-channel infill deposits above fluvial and estuarine sediments of Pleistocene age. Preliminary estimates indicate 32 million cubic yards of sand deposited in a shoal feature offshore of Sandbridge, and 19 million cubic yards of sand in deposits offshore of Wallops Island in the upper 5 feet of the seafloor. Additional data collection is needed to assess the full extent of these and other identified deposits.

Marine sediments from new and previously-collected cores and grab samples have been analyzed for heavy minerals including ilmenite and rutile, zircon, and monazite, which are sources of titanium, zirconium, and rare earth elements, respectively. To date, mineral concentrates from about 580 sediment samples have been analyzed for total heavy mineral (THM) content, with 19 percent containing >5 percent THM, and 2 percent containing >10 percent THM. Ongoing studies are focused on mineral associations, depositional factors, and likely on-shore source areas.