Please do not destroy or throw away this publication. If you have no further use for it, write to the Geological Survey at Washington and ask for a frank to return it UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. C. Mendenhall, Director Bulletin 867 ~`irr GEOLOGY OF THE COASTAL PLAIN OF SOUTH CAROLINA BY C. WYTHE COOKE ,k..r OP V-,,,, • 4., 9?, ,..k- ....,..„,„.„.....-..o...a, —..-_,.. IA ( 33 a 111 a UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1936 For sale by the Superintendent of Documents, Washington, D. C. Price 80 cents CONTENTS Page Abstract 1 Physical geography 2 Geographic provinces 2 Geographic divisions of the Coastal Plain of South Carolina 3 Coastal terraces 4 Pamlico terrace 6 Talbot terrace 7 Penholoway terrace 8 Wicomico terrace 8 Sunderland terrace 8 Coharie terrace 9 Brandywine terrace 9 Aiken Plateau 9 Richland red hills 10 High Hills of Santee. 10 Congaree sand hills 11 Drainage 11 Principal streams 11 Development of the drainage 13 Stratigraphy 14 Formations included 14 Upper Cretaceous series 15 General features 15 Tuscaloosa formation 17 Black Creek formation 25 Peedee formation 32 Eocene series 39 Correlation 39 Black Mingo formation 41 McBean formation 55 Deposits of Jackson age 72 General character 72 History of the names "Santee" and "Cooper" 73 Santee limestone 75 Cooper marl 82 Barnwell sand 89 Oligocene series 96 Flint River formation 98 Miocene series 99 General features 99 Hawthorn formation 101 Raysor marl 115 Duplin marl 117 Pliocene series 123 General features 123 Waccamaw formation 124 III IV CONTENTS Stratigraphy—Continued. Page Pleistocene series 130 Fluctuations of sea level 130 Marine formations 130 Brandywine formation 131 Coharie formation 132 Sunderland formation 136 Wicomico formation 143 Penholoway formation 147 Talbot formation 148 Pamlico formation 149 Geologic history 154 Structure 158 Mineral resources 159 Metals 159 Nonmetals 159 Phosphate rock 159 Limestone and calcareous marl 159 Clay 160 Sand and gravel 161 Mineral fuels 161 Ground water 161 Sources 162 Description by counties 164 Aiken County 164 Allendale County 165 Bamberg County 166 Barnwell County 166 Beaufort County 167 Berkeley County 168 Calhoun County 169 Charleston County 170 Chesterfield County 171 Clarendon County 171 Colleton County 172 Darlington County 173 Dillon County 175 Dorchester County 176 Florence County 177 Georgetown County 179 Hampton County 180 Horry County 181 Jasper County 182 Kershaw County 182 Lee County 183 Lexington County 183 Marion County 184 Marlboro County 184 Orangeburg County 185 Richland County 186 Sumter County 186 Williamsburg County 187 Index 189 ILLUSTRATIONS Page PLATE 1. Map showing the distribution of the Pleistocene terraces and the original extent of the Pleistocene formations in South Carolina In pocket 2. Geologic map of the Coastal Plain of South Carolina In pocket 3. A, A sand dune on Folly Island; B, Stumps on the beach at Folly Island; C, Encroachment of the sea on Folly Island___ 2 4. Land and sea in Pamlico time 10 5. Land and sea in Talbot time 10 6. Land and sea in Penholoway time 10 7. Land and sea in Wicomico time 10 8. Land and sea in Sunderland time 10 9. Land and sea in Coharie time 10 10. Land and sea in Brandywine time 10 11. A, Erosion in the Aiken Plateau exposing the Upper Cretaceous Tuscaloosa formation on upper Aiken-Graniteville road 4 miles west of Aiken; B, Tuscaloosa formation 2 miles northeast of Middendorf 18 12. A, Tuscaloosa formation 1 mile north of Langley; B, Mars Bluff, Pee Dee River 19 13. A, Tuscaloosa-Black Creek (?) contact 1 mile west of Wedge- field; B, Dewitts Bluff, Pee Dee River 26 14. A, Contact between the Black Mingo formation and the McBean formation near Bates Mill, Calhoun County; B, Marl pit at Lambs 27 15. A, Barnwell sand in railroad cut at Aiken; B, Sandstone of Barnwell age on the Dibble farm 5% miles southeast of Aiken 90 16. A, Barnwell sand near Bethel Church, Lexington County; B, Unconformity between the Hawthorn formation (f Marks Head marl) and the Duplin marl above Enochs wood landing, Savannah River, 67% miles above Savannah__ _ 91 17. Mosaic of aerial photographs of part of Horry County between Waccamaw River and the ocean 154 18. Map showing the approximate original distribution of phosphate deposits in South Carolina 154 FIGURE 1. Geographic divisions of the Coastal Plain of South Carolina 4 2. Ideal profile across the coastal terraces 6 V GEOLOGY OF THE COASTAL PLAIN OF SOUTH CAROLINA By C. WYTHE COOKE ABSTRACT The Coastal Plain of South Carolina extends from the Atlantic Ocean inland a distance ranging from 120 to 150 miles to the Fall Line, where it adjoins the Piedmont province. It includes an area of more than 20,000 square miles, or nearly two-thirds of the State, whose total area is 30,981 square miles, of which 494 square miles is water. The geographic divisions of the Coastal Plain are the marine coastal terraces, or "low country", which stand less than 270 feet above sea level, and the Aiken Plateau, the High Hills of Santee, the Richland red hills, and the Congaree sand hills. Few places in the Coastal Plain are as high as 600 feet above sea level. The coastal terraces together have an area more than twice as great as all the rest of the Coastal Plain. The landward limit of each terrace is defined by the level shore line at which the sea'and its estuaries stood when the terrace was under water. The seaward limit is the shore line of the next lower terrace. The names of the terraces and the approximate present altitude of the shore line of each are as follows: Pamlico, 25 feet; Talbot, 42 feet; Penholoway, 70 feet; Wicomico, 100 feet; Sunderland, 170 feet; Coharie, 215 feet; Brandywine, 270 feet. The present shore line, which bounds the Recent terrace, has a total length of 1,241 miles, including 281 miles of mainland and NO miles around islands. The Coastal Plain is drained by three large through-flowing, rivers—the Pee Dee, the Santee, and the Savannah—and by many smaller streams. The drainage pattern of the uplands was well established before the beginning of Pleistocene time; that of the coastal terraces is more youthful. The Coastal Plain of South Carolina is underlain by sedimentary deposits ranging in age from Upper Cretaceous to Recent, which lie unconformably on ancient crystalline rocks. There are three Upper Cretaceous formations—the Tuscaloosa formation, composed chiefly of light-colored sand and clay; the Black Creek formation, consisting in its lower part of dark-gray to black leaf-bearing laminated sand and clay and in its upper part of the sandy Snow Hill marl member, which contains marine fossils; and the Peedee formation, composed chiefly of gray sand and marl-stone. The Eocene series is represented by the Black Mingo formation, of Wilcox age; the McBean formation, of Lisbon (Claiborne) age; and the Santee limestone, the Cooper marl, and the Barnwell sand, all of Jackson age, the last apparently equivalent to both Santee and Cooper. All the Eocene formations contain marine shells. The only representative of the Oligocene series is the Flint River formation, which occupies a small area in Allendale County but extends westward across Georgia and into southeastern Alabama and northern Florida. 1 2 COASTAL PLAIN OF SOUTH CAROLINA The Miocene series includes the phosphatic Hawthorn formation, whose typical occurrence is in Florida; the Raysor marl, a shell bed that is in part equivalent to the lower part of the Yorktown formation of Virginia and to the lower part of the Choctawhatchee formation of Florida; and remnants of the Duplin marl, whose type locality is in North Carolina. The Pliocene series is represented by the Waccamaw formation, composed chiefly of marine shell beds, and by high-level terrace deposits. The seven Pleistocene formations have the same names as the Pleistocene ter- races and are limited by the same shore lines. They consist chiefly of sand, but the younger ones contain clay and marine shells. The geologic history of South Carolina records many advances and retreats of the sea during which sediments were deposited and planed off time and again. Many of the formations that were once continuous now persist only as small remnants. The shiftings of the shore line during Pleistocene time are regarded by the writer as due partly to glacial control of sea level. The dominant structural feature of the Coastal Plain of the Carolinas is the "Great Carolina Ridge", whose axis lies near and parallel to the boundary •between North and South Carolina. The downwarp of the region southwest of it during late Eocene time caused the Jackson sea to transgress across older formations and to flood the borders of the Piedmont in Georgia. Upon the beveled surface of the ridge lie thin patches of nearly horizontal Miocene and Pliocene shell beds and more extensive sheets of Pleistocene terrace deposits. Enrichment of the phosphatic marl or limestone of the Miocene Hawthorn formation gave rise to valuable deposits of phosphate rock in the coastal region of South Carolina. The principal deposits of limestone and marl are in the Santee limestone and the Cooper marl, both of which are available in large quan- tity. Valuable deposits of kaolin in the Tuscaloosa formation are worked in several counties; the Barnwell sand contains some fuller's earth; and there are extensive deposits of clay suitable for making brick and tile in terraces along the principal rivers. Sand and gravel are widely distributed. Most of the geologic formations of the Coastal Plain contain considerable water.