Sweetwater Creek State Park - Geology

Geology

Geologic history

The historical geology of the Sweetwater Creek State Park is divided into three periods such as deposition of sediments, metamorphism and folding, and uplift and erosion.

Deposition

The rocks at the surface at the park were deposited at least 450 million years ago. A sequence of sediments formed rocks such as shales, sandstones and greywackes. When these sediments were deposited, the environment was similar to that off the coast of Georgia today. These deposits were formed constantly through layering of older deposits by younger ones. Later these deposits were covered by basaltic lava. Eventually, the lava cover was mantled by thousands feet of sediments.

Metamorphism and Folding

It is likely that the deposition continued until 450 million years before the present causing increase of weight of the sediments in the basin. When subsidence stopped uplift began due to compression of the subsidence from the sides. Due to the compression, temperature and pressure rose which led to a reformation of the rocks in the basin. Increasing temperature led to recrystallization of minerals in the rocks. As the result of recrystallization the micas were preferentially oriented, or oriented in the same position. Due to this orientation, foliation took place. Recrystallization and foliation changed the shales, sandstones, greywackes and basalts into mica schists, quartzites, metagraywackes and amphibolites. It is likely that metamorphism destroyed fossil remains that may have been in the rocks. Along with metamorphism folding and faulting of the rocks took place. There were two periods of the folding in the park. Pressure led to breach of the rocks.

Uplift and Erosion

Until approximately 250 million years ago uplift, folding, and faulting of the rocks took place. During and after uplift streams changed landscape. Streams carried away dissolved organic acids and groundwater decomposed the rocks. These processes take place today in the park. The washed sediments were found in the Coastal Plain of Georgia. Due to the erosion, the rocks below several miles are exposed to the earth's surface.