GEOLOGY OF CAROLINA SAND-HILL COUNTRY. 33 



The next paper was entitled : 



GEOLOGY OF THE SAND-HILL COUNTRY OF THE CAROLINAS 



BY J. A. HOLMES 



- [Abstract] 



The coastal plain region of the south Atlantic and Gulf states is covered almost 

 everywhere with a thin mantle of loose material, mostly loam, clay or sand, the 

 latter predominating, and the general surface is either nearly level or gently undu- 

 lating. Near the inland border of the region the topographic features and the 

 sand-covering are more pronounced. In the Carolinas the sand-covered ridges and 

 hills reach an elevation of 400 to 600 feet, while the brooks at their bases, within 

 half a mile of the summits, run at a level of 100 feet, more or less, below, and the 

 larger streams which separate the ridges and divides are but little above tide-level. 

 Hill and valley alike are covered with a mantle of sand, which varies in thickness 

 from 1 to 20 or 30 feet. This pronounced topography and sand-covering have 

 given rise to a somewhat general use of the expressions " sand-hill country " and 

 'among the sand-hills." These expressions are sometimes applied locally to sec- 

 tions of the coastal plain region near the sea, where the wind-action has produced 

 dunes, but such usage is local. 



That part of this region which lies between the Neuse and Savannah rivers has 

 been examined more particularly, and in this region the following sections will 

 indicate fairly well the geologic structure: 



a. A series of cross-lidded, medium to coarse arkose sands lying on the irregu- 

 larly eroded surface of the crystalline rocks. These beds, which are classed pro- 

 visionally as Cretaceous, Contain in the upper layers in places lenses of clay and 

 occasional thin beds and seams of lignitic material. They have been deeply 

 eroded, their present surface rising nearly to the tops of the highest hills and sink- 

 ing to the level of the deeper valleys. 



6. Overlying these arkose sands near the tops of a few of the higher hills are to 

 be found small patches of older Eocene deposits, remnants of a once extensive 

 formation. 



c. Overlying with marked unconformity the deeply eroded Cretaceous surface 

 and the Eocene remnants are the loams and ferruginous sands of the Lafayette 

 formation, which in turn have been deeply eroded and entirely removed over con- 

 siderable areas in the drainage basins of the larger streams. 



d. Spread out over this deeply and irregularly eroded surface, resting in places 

 on the Lafayette or the Eocene or on the Cretaceous, or where all of these have 

 been removed, even on the crystalline rocks, lies the mantle of sand and loam 

 which is classed as Columbia. 



Among the features in this region deserving special consideration may be men- 

 tioned the following : 



1. The arkose sands, here classed as Cretaceous, which have a thickness in this 

 region of several hundred feet, and near the coast a thickness of possibly more 

 than 1,000 feet, indicate the removal of a large amount of material from the adja- 

 cent Piedmont plateau during Cretaceous time while this plateau was being reduced 

 to base-level. The origin of the extensive beds of typical arkose material has not 

 yet been satisfactorily explained. 



V— Bum.. Geoi,. Soc. Am., Vol. 5, 1893. 



