SURFICIAL AND BEDROCK GEOLOGIC MAP OF HORSESHOE BEND NATIONAL MILITARY PARK: THE STRUCTURAL AND LITHOLOGICAL CONSTRAINTS ON THE OUTCOME OF THE BATTLE OF HORSESHOE BEND

Appalachian structures and lithologic sequences underlying the Horseshoe Bend National Military Park played an important role in framing a decisive American victory. The Battle of Horseshoe Bend, on March 27, 1814 effectually ended the Creek Indian War. Our studies within and around the park include: bedrock and surficial 1:24K geologic mapping; petrographic thin section analysis; statistical geometric and kinematic structural analyses, and Ar-Ar mineral cooling studies. Sheared, NE-striking Jacksons Gap Group lithologies define the Brevard zone, a fundamental Appalachian fault zone, and are much more susceptible to weathering than are the higher-grade and more thoroughly re-crystallized eastern Blue Ridge (EBR) and Inner Piedmont terranes that constrain them. The Tallapoosa River’s course followed the deeply eroding Jacksons Gap units along the southeast side of the horseshoe-shaped bend. It broke across strike of the Abanda fault, which forms the border with the EBR, as it flowed westward to form the hinge zone of the river bend. Weaker schist units in the EBR give way westward to more resistant tabular granite intrusions (Kowaliga Gneiss and Zana Granite) and the river anastomoses through these lithologies,creating islands of granite, before reestablishing a strike-parallel course that defines the northwest side of the horseshoe;. Thus, structural and lithologic control of the river’s course created the “horseshoe” peninsula used by General Andrew Jackson to corner and defeat the Creek Indians.