SCARPS, RIDGES, AND SWALES: THE ROLE OF COASTAL PLAIN GEOLOGY AT THE BATTLE OF GREEN SPRING, AMERICAN REVOLUTION

On July 6, 1781 an American army under the command of Gen. Lafayette engaged Gen. Cornwallis’ British army between Green Spring Plantation and Jamestown Island (~8 km SW of Williamsburg) on the Virginia Coastal Plain. The British army was moving its base of operation to the south of the James River, while the Americans troops were harassing the British army’s rear. American forces hoped to strike a blow to the British troops that awaited transport across the James River. The landscape played a significant role in the battle- dictating both the track that American troops took in attacking the British, and providing cover for Cornwallis to conceal his troops prior to the general engagement. We use LiDAR and borehole data to better understand the Coastal Plain landscape and the underlying stratigraphy, and relate those factors to the battle.

Green Spring, a 17^th century house and plantation, served as the center from which the American attack originated, and is located on a ~25 m upland underlain by the early Pleistocene Bacons Castle Formation. The landscape around Green Spring is stair-stepped with erosional scarps and broad flats underlain by younger Pleistocene units that form transgressive estuarine sequences associated with sea-level high stands. Green Spring Plantation is fronted to the south by the Kingsmill scarp, an erosional landform with ~10 m of relief. South of the Kingsmill scarp, American troops advanced across a ‘causeway’, a low ridge with 1-2 m of relief. This ridge, underlain in part by the Elsing Green Alloformation, was easier to traverse than the swampy abandoned meander of Powhatan Creek to the east, and the dissected terrain to the west. This subtle ridge and swale topography had likely formed through rapid shoreline progradation of the ancestral James River.

Cornwallis set a trap, stationing the bulk of his troops behind a younger late Pleistocene scarp and effectively out-of-sight to the advancing Americans. From these positions the British counterattacked, and nearly enveloped the American forces. Fresh American troops were called in to cover the American retreat to Green Spring with fighting ceasing at dusk. Tactically, the battle was a British victory, but American forces fought well, and the next day the British troops crossed the James River leaving the American army in control of the Virginia Peninsula.