Santee Submergence, Example of Cyclic Submerged and Emerged Sequences
Subsurface geologic maps obtained through auger drilling investigation in east-central South Carolina illustrate cyclic development of terrace formations during continental submergence and emergence. Ancient estuarine deposits form part of these terrace formations. The history of filling of two valley systems, the Piedmont draining Santee River and the Coastal Plain draining Cooper River, are examined through three-dimensional stratigraphic sequences in the Illinoian-Sangamon and in the Holocene. Initial erosional disconformities are succeeded by alluvial aggraded bed load and overbank sediments, estuarine clay and marsh clay fills, shoestring channel fill sands, and deltaic sediments that prograde seaward. The Holocene estuaries are in a very early stage of the continental and marine submerged cycles, compared to the full cycle sediments of the ancient units.