COASTAL AND FLUVIAL LANDFORMS: HORRY AND MARION COUNTIES, SOUTH CAROLINA.
LOUISIANA STATE UNIV BATON ROUGE COASTAL STUDIES INST
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Horry and Marion counties have many geomorphic characteristics typical of the outer portion of the Atlantic Coastal Plain. The sequence of coastal and fluvial deposits reflects five phases coastal progradation, designated Horry, Conway, Jaluco, Myrtle, and Recent. During each phase a depositional surface has been built composed of a barrier island behind which has accumulated quite-water backbarrier-flat and fluvial sediments. A sixth depositional surface composed entirely of fluvial sediments Terrace I has also been mapped. Differences in elevation, soil development, dissection, degree of preservation of primary morphology, and stratigraphic relations indicate that four major transgressions and possibly two minor transgressions are responsible for the depositional morphology. In the periods between Horry and Conway-Jaluco, Conway-Jaluco and Myrtle, and Myrtle and Recent, major regressions of the sea occurred during which time the surfaces were exposed to fluvial dissection, soil development, and partial wind deflation. During the intervals which separate Conway-Jaluco from Myrtle and Myrtle from Recent, two minor regressions-transgressions may have taken place leading in the first instance to the development of the Jaluco surface, and in the second instance to Terrace I. The changing nature of geomorphic processes accompanying the fluctuations of sea level in late Cenozoic times has lead to a complex pattern of landforms which have been superimposed upon the primary depositional morphology. These include entrenched drainage basins, benched valley sideslopes, localized fluvial terraces, sinkholes, Carolina bays, and valley dunes. Author
- Geology, Geochemistry and Mineralogy