166 BALL AND STANLEY-BROWN — APALACHICOLA RIVER GEOLOGY. 



already shown, that an elevation took place which raised the area of 

 the marl to a point where the deep-water fauna forsook it, where vege- 

 table matter was deposited, and where finally the water w^as so shoal as 

 to admit of cross bedding from wave-action. These features are charac- 

 teristic of the beds at the point A-B, figure 2, where our chief section was 

 made ; but, following them northward in the face of the bluff for about 

 a third of a mile, we perceive that a change takes place in the character 

 of the sediments of which the bed is composed. They become more 

 clayey and the sand is finer; the color changes from pale yellow to 

 Avhitish, and finally to a pale gray or even a greenish tint. At point C, 

 figure 2, the transformation is complete, and the yellow color and cross- 

 bedding have disappeared entirely. In the bed at this point we did 

 not observe any fossils, but its thickness is about the same as at B. 

 Five miles further north, in the Rock bluff antichne, this bed reappears 

 with a thickness of 63 feet, and here contains oyster-bed fossils, Ostrea, . 

 Peden, Balanus, Anomia and Ticrritella, and it is again seen with the 

 same fossils at Aspalaga. At Old Chattahoochee landing it is again 

 unfossiliferous. It is also reported under the Chesapeake, at Jacksons 

 bluff, on the Ochlockonee river, where it has the same fossifg as at Rock 

 bluff. This deposit clearly belongs to the Chipola series and represents 

 that part of the latter which was deposited in shallow water, before the 

 incursion of the Chesapeake fauna, during an epoch of elevation. The 

 greatest thickness of the Alum bluff beds observed at Rock bluff is 

 63 feet. They were subsequently named the "Aspalaga marl " by John- 

 son,* and referred to his " Waldo formation," but they are physically 

 continuous with the sands of the Alum bluff beds. 



Farther west, at Oak Grove, on the Yellow river, Florida, what appears 

 to be this same fauna occurs in a fine incoherent gray sand, with a 

 number of species not found in the Chipola marl, including the Turriiella 

 (n. sp.), referred to as occurring at Rock bluff. It would seem, there- 

 fore, that this same zone is represented at that point, though the matrix 

 is different. With a large number of these essentially old Miocene fossils 

 collected at Oak Grove were sent by Professor E. A. Smith specimens of 

 Pecten madisonius, Panopsea goldfassii and several other fossils, which latter 

 occur in the Chesapeake at Alum bluff, but not in Maryland. These 

 may represent a stratum above that in which the old Miocene fossils 

 occur, or these species may be the precursors in that part of the Alum 

 bluff beds of the advancing Chesapeake fauna. At present, owing to 

 various circumstances, which need not be recapitulated here, we incline 



* Bull. Geo!. Soc. Am., vol. 3, p. 130. On page 129 they are called in a foot-note the "Aspalaga clays," 

 but clay is not predominant in them. The Waldo horizon is that of the newer Miocene (Chesapeake) 

 at the typical locality, but its author in defining it combined with it beds at other localities belong- 

 ing to the old Miocene. 



