516 PROCEEDINGS OF PHILADELPHIA MEETING. 



exposures in many small side branches, particularly in those which flow from' 

 the southward. These head in a plateau of Eocene overlain by the Lafayette 

 formation, and they cat more or less deeply into clays and sands of the Potomac 

 formation before they reach the low, swampy flats adjoining the river. At Fort 

 Motte there is a high bhiif h'ing a short way back from the river, in which the 

 Potomac beds are seen overlain by the Eocene marls and dark clays containing 

 abundant fossils. 



In my trip down the Peedee river from Cheraw I traveled in a small skifl", and 

 although I made a careful search for outcrops I found very few. It was not long 

 after a freshet and the water was still quite high, so that possibly a greater num- 

 ber of exposures would have been seen at low water. Low banks of Columbia 

 formation and wide areas of swamps were the only features that I observed except- 

 ing a short scarp at Gardners bin tt', 10 miles below Cheraw, and Hunts bluff, 20 

 miles farther down. In Gardners blutt' the following section was noted : 



1. Orange and buff sand loam 5 feet 



2. Orange sand with pebbles, cross-bedding 6 " 



3. Coarse gray sand with buff streaks 5 " 



4. Coarse gray sand, somewhat cross-bedded; lines of clay and quartz 



pebbles 10 " 



5. Fine gray sandy clay, massive ; contains indistinct lenses of purer clay. . 8 " 



Numbers 2 and 3 are sharply separated throughout by a slightly waving line ; 

 numbers 4 and 5 are separated by a moderately sharp break, which is quite irregu. 

 lar at several points. Beds 1 and 2 are probably Lafayette in age and the under- 

 lying deposits are undoubtedly Potomac formation. At Hunts bluff there is a 20- 

 foot exposure for about 200 feet along the northeast bank of the river. At its base 

 it exhibits gray, cross-bedded sands, with a few scattered (inartz pebbles; next 

 there is an irregular bed of pebl)ly sands and then stratified gray to brown sands, 

 merging upward into brown-buff loams at the surface. The basal beds ai)i)('ar to 

 be Potomac, but the evidence is not conclusive. A short distance eastward in the 

 higher lands about Bennettsville there are observed the marls of marine Cretaceous 

 age, which overlies these Potomac beds. The marls come to the river l)ank at 

 Mars bluff, below the railroad bridge, 10 miles east of Florence, in a fine series of 

 exposures which have been briefly described by Tuomey. The Potomac beds there 

 are sands and clays of the usual character, and they pass ])eneath the river a short 

 distance below. The marine Cretaceous marl and marlstone contain abundant 

 distinctive fossils, and they are in turn overlain by fossiliferous Eocene marlstone 

 for some distance. 



Several deep wells in South Carolina have penetrated the Potomac beds and 

 their records throw some additional light on the relations. The well in the village 

 of Aiken was bored thfough the formation at a point near the western edge of the 

 Eocene, and consequently it exhiljits the fall thickness of the Potomac. The fol- 

 lowing record is given : 



0-45 feet red clay. Lafayette. "] 



45-100 " sand. • | 



100-1.)0 *' "chalk." Mixture of flue white sand and kaolin. [Potomac. 



130-405 " sand and soft sandstone ; some clay. | 



465-741 " granite. J 



A well at Florence, having a depth of 1,335 feet, passed through Miocene, marine 

 Cretaceous and Potomac formations, and at 608 feet entered typical red sandstone 



I 



