The swamp was formed over the past 6,500
years by the accumulation of peat in a shallow basin on the edge of an ancient
Atlantic coastal terrace, the geological relic of a Pleistocene estuary. The
swamp is bordered by Trail Ridge, a strip of elevated land believed to have
formed as coastal dunes or an offshore barrier island. The St. Marys River and
the Suwanee River both originate in the swamp. The Suwanee River originates as
stream channels in the heart of Okefenokee Swamp and drains at least 90% of the
swamp's watershed southwest towards the Gulf of Mexico. The St. Marys River,
which drains
