on the Geological Survey of South Carolina. 67 



Older secondary rocks. — New Red Sandstone. — This rock, 

 which is found at intervals from Massachusetts south, finally ter- 

 minates in South Carolina, four or five miles from the northern 

 boundary, overlying in this State the clay slates unconformably. 

 Trap dikes penetrate it, and the sandstone is much altered by it, 

 sometimes so as to resemble porphyry, having crystals of feldspar 

 imbedded in a black gangue. Veins of carbonate of lime are also 

 found in the sandstone. 



Upper secondary or cretaceous rocks. — The cretaceous 

 formation of South Carolina next conies under the notice of our 

 author, for as he remarks, " there is a wide gap in the geological 

 series of South Carolina, extending from the metamorphic rocks 

 to the upper secondary, and unfortunately among the missing 

 rocks, we find the carboniferous system, with its coal measures." 



The cretaceous deposits are described as appearing upon the 

 surface in Horby district, where the strata dip beneath the sands 

 of the coast and are covered by tertiary beds, also at a number of 

 other localities in this and the neighboring districts. They are 



composed generally of marl, marl stone, and shales. It is re- 

 markable that the green sand so characteristic of this formation 

 HI New Jersey and Delaware, is absent in the beds of the same 

 age in South Carolina, and still appears again in deposits of a 

 later period. 



The fossils of these deposits are not numerous, the following 

 list comprising all yet known. 



Carcharodon, (species?) Pectunculus liamula, Mort. 



Lamna, (species?) Anomia argentifera, " 



Ammonites placenta, Dekay. Trigonia thoracica, 



Belemnites vertebroides, Morton. " crenulata. 



Natica petrosa, " Cardium altum. 



Ostrea cretacea, " " (species?) 



Exogyra costata, Say. Crassatella vadosa, Mort. 



Plagiostoma dumosum, Mort. Hamulus onyx, Mort. 



Cuculla?a ovata. 



Tertiary series.— The tertiary deposits of South Carolina are 

 distinguished from those of the cretaceous, not less in their mm- 

 eralogical than in other characters. Instead of the dark marls 

 and marl stone which prevail in the latter, we find in the tertiary 

 deposits, thick strata of limestone, highly calcareous marl, with 

 beds of loose sand, clay aud gravel. From the coast, they cover 

 th e surface of the slate inland, with the exception of the small 

 patches of cretaceous rocks, for a distance of more than one hun- 

 dred miles, occupying about two-thirds its whole extent. Along 

 a 'me from the Savannah near Hamburg, to Thompson's creek, 

 ^ vh ere it enters the slate from North Carolina, is found their 

 boundary, and they are here observed resting immediately upon 



