LATER TERTIARY (MIOCENE AND PLIOCENE). 807 



Carolina. The four species which have not as yet been reported from there occur in other 

 localities in horizons the stratigraphic equivalent of the Duplin, or in deposits of later age. 

 Bed No. 5, therefore, can be definitely correlated with the Duplin marl of North Carohna and 

 the fossUiferous Miocene marls of Darlington and Mayesville, S. C. 



"The Marks Head marl, which was first named by Sloan and is represented by bed No. 4 

 of the section, contains specimens of the genus Carolia, which suggests an Oligocene age, but 

 every other identifiable species may be Miocene, and only three of them range downward into 

 the Oligocene. Nine of the species are not known below the Miocene, and of these nine, six are 

 confined to the Miocene. The horizon is, therefore, Miocene, while the presence of TurriteUa 

 sequistriata Conrad, Calliostoma apJielium Dall, Ostrea mauricensis Gabb, and Peden marylandicus 

 Wagner definitely points to a horizon low in the series, approximately equivalent to the Calvert 

 formation of Maryland. 



"The recognition of the stratigraphic position of this horizon is of importance, as it is the 

 only low Miocene horizon known south of Virginia. Farther south in Florida, along the western 

 extension, on the Ocklockonee and Apalachicola rivers, the Miocene rests upon the eroded sur- 

 face of the upper Ohgocene. The Miocene deposits of these locaHties represent a horizon high 

 in the series. Therefore, the Marks Head Miocene is the equivalent in part to the erosion 

 interval between the upper Oligocene and the Miocene of western Florida. 



"Bed No. 2 of the section at Porters Landing contains fossils indicative of an upper Oligo- 

 cene age. Bed No. 3 is very likely of Miocene age, and the line of rounded pebbles at the base 

 suggests that the Miocene may rest upon the eroded surface of the upper Oligocene. It seems 

 probable that along the Savannah River an erosion interval occurred between Oligocene and 

 Miocene depositions, but the interval was of shorter duration than in western Florida." 



The Marks Head marl is the oldest Miocene known south of the Hatteras axis. Sloan has 

 applied the name Edisto marl to the indurated phosphatized marl in the vicinity of Charleston, 

 the source of the rich phosphate deposits of that area. This material overlies the Cooper marl 

 (Eocene) and underlies the Pleistocene and is only 2 or 3 feet thick. Although the identifiable 

 fossils from it are few, stratigraphic equivalence with the St. Marys formation of Maryland and 

 Virginia is deficnitely suggested. The Edisto marl is overlain by a softer, yellow sandy marl 

 near the old Cohen plantation, three-fifths of a mile west of Goodrich station. To this marl 

 Sloan has apphed the name Goose Creek marl. According to Sloan it is overlain by the Duplin 

 marl. The following section at Davis Landing, on Peedee River 16| miles N. 75° E. of Lake 

 City, shows the relations of the beds : 



Feet. 



5. Pleistocene sands and loam 8 



4. Indurated ledge of dirty yellow marl containing Pecten eboreus, especially at the base 16| 



3. Compact yellow marl with large numbers of Chama striata and Area incile 8 



2. Friable yellow marl, containing Amusium mortoni and Pecten eboreus (Goose Creek marl of 



Sloan) 4i 



1. Dark blue-green marl, with Cretaceous fossils 23 



60i 



Beds Nos. 3 and 4 represent the Duplin marl. The faunal affinities of the "Goose Creek" 

 marl have not yet been positively determined. The Duplin marl is an extension of the marl 

 of the same name in North Carolina southward into South Carolina, where it is well developed 

 along Peedee River and in the vicinity of Darlington, Mayesville, and Porters Landing, the 

 last-mentioned locality being on the Georgia side of Savannah River. 



Otto Veatch, in the manuscript of a report that has been published since this discussion 

 was compiled, gives the following account of the Miocene in Georgia: 



"Miocene strata have been discovered in the bluffs of Savannah River in Screven and 

 Effingham counties; on Altamaha River near Doctortown, Wayne County; at Brunswick; and 

 at Owens Ferry, on Satilla River in Camden County. 



"The Marks Head marl is typically exposed near Porters Landing, on Savannah River, 

 Screven County. It has not been differentiated at other localities than the bluffs of this river. 



