58 Bulletin 15 368 



the Chattahoochee limestone and the overlying sandy clays (As- 

 palaga clays). 



In the clays, at a height of about 30 feet, the base of a PeElen 

 and Placuna bed was observed, and, separated from this by sandy 

 clays, another PeBen bed was found at a height of about 50 feet. 



Average dip of the Pe£len arid Plaaina layer. If we suppose 

 the layer containing Peflen and Placuna to be the same at Aspal- 

 aga, Camp Scott and Rock Bluff, we find a dip of 118 feet during 

 the five miles between Aspalaga and Rock Bluff, or an average 

 descent, southward, of 23 feet in a mile. That this dip is steeper 

 toward the north is shown by the following rate of slope: 



Aspalaga to the ravine, yk mile, 10 feet, or 80 feet per mile. 

 Aspalaga to Camp Scott, 2 miles, 70 " "35 " " 

 Camp Scott to Rock Bluff, 3 " 48 " " 16 " " 



The sedlion of the bluff corresponds nearly with one made by 

 Dr. Dall.* In the latter, however, a somewhat greater thickness 

 is assigned to the limestones and clays. 



Sellion at Alum Bluff {see page 37). At Alum Bluff, 3 miles 

 below Rock Bluff, a se<ftion was also made. The total height of 

 the bluff above water level at the time of se<5lioning was found to 

 be 148 feet. The Chattahoochee limestone is no longer visible, 

 and the fossiliferous Chipola sands, obscured in part by a talus, 

 are found a few feet above the river. These sands are overlaid by 

 some 19 feet of cross-bedded sands, constituting the Alum Bluff 

 transitional beds, and underlying the fossiliferous Chesapeake 

 Miocene. The se(ftion, in general, agrees with that of Dr. Dall.f 



The Chipola marl. The Chipola marl is a compacfl mixture 

 of broken shells, sand and clay. At Alum Bluff, the color of this 

 deposit is dark red, owing to the presence of iron peroxide, but 

 usually, at other localities, it is light yellow. 



Chipolan species from Alum Bluff. The following species| 



"'^ Bull. Geol. Soc. Amer., vol. 5, 1895, p. 156. 

 '\ Ibid., p. 157. 



X For original descriptions and references, see Dall, Trans. Wag. Free 

 Inst. Set., vol. 3, pts. 1-6. 



