GEOLOGY AND GEOMORPHOLOGY OF THE ROCKY CREEK RAPIDS NEAR THE CONFLUNCE WITH THE CATAWBA RIVER, GREAT FALLS, SOUTHEASTERN CHESTER COUNTY, SOUTH CAROLINA
Near Great Falls, SC the river has cut a deep channel through saprolite exposing an extensive boulder field and bedrock of the Great Falls Metagranite (GFM). Before the Catawba was dammed, the river eroded 22-30 meters in five km. to produce the Great Falls, a series of rapids and waterfalls.
The gradient of Rocky Creek is approximately 9.6 feet/mile. Near its confluence with the Catawba River, it flows over granite boulders, rock islands, and residual rock smoothed by constant water flow. The rapids of Rocky Creek were exposed during Pleistocene sea level fluctuations, glacial and interglacial episodes, increased gradients downcut and removed saprolite along steeper slopes exposed widespread single and multiple corestones.
The (GFM ) is located in the Carolina terrane near the boundary between the Carolina Slate belt and The Charlotte belt, the area is underlain by metamorphic rocks ( gneiss, schist, phyllite, metasedimentary and metavolcanic) intruded by several types of plutonic rocks, included are granite, diorite, and diabase. Rocks are Late Proterozoic to Cambrian and they resemble igneous rocks in the Carolina slate belt, intrusive rocks with calc-alkaline affinity, and in other parts of the Piedmont.The GFM is a nearly circular, 40 square mile, 543 +/- 63 m. y. O. (Fullagar, 1971) (Cambrian or Neoproterozoic Era, metamorphosed granite composed of quartz, feldspar and mica, probably a crystallized magma chamber, forced upward into sediments, volcanic rocks, metamorphic and igneous rocks and is cut by north - northeast striking meta-mafic dikes. Tectonically, this area is an uplifted subducted boundary margin of Cambrian oceanic island arc boarded older continental crust.