170 ' DALL AND STANLEY-BROWN — APALACHICOLA RIVER GEOLOGY. 



theless a continuation of the more homogeneous formation to the north- 

 ward, the modifications having been brought about by the agencies to 

 which it was subjected in its seaward extension. There would seem to 

 be no question as to the propriety of referring it, as we have done, to the 

 Lafayette of Hilgard and McGee, and from the studies of the fossil- 

 bearing beds alone it can be stated with a reasonable degree of certainty 

 that it is not earlier than the Pliocene. 



PLEISTOCENE. 



In almost every instance there was observed resting upon the preced- 

 ing formation a veneer 3 or 4 feet thick of incoherent, superficial sand, 

 which in nearly all cases has the appearance of such fine sandy mate- 

 rial as is deposited in the sea by the sluggish southern rivers. At Alum 

 bluff it presents more the aspect of washed beach-sand, but in all ex- 

 posures examined bowlders and large pebbles were conspicuously absent. 

 The opportunities for studying this surface bed were too limited to war- 

 rant the presentation of any positive opinions as to its relation to similar 

 materials of the region to the eastward or westward. It is probably, 

 however, a remnant of the Pleistocene Columbia, which, along the sea- 

 ward portion of North Carolina, South Carolina and Georgia, has been 

 found by McGee and others to cover the Lafayette as a mantle of vary- 

 ing thickness. 



Correlation. 



The following preliminar}^ correlation of the Miocene beds differs 

 slightly from that of Bulletin 84, United States Geological Survey, and 

 also from that of Mr Foerste, owing to the receipt of additional material 

 and our personal later observations on the ground. More knowledge is 

 required both of the fossils and the stratigraphy before a finality can be 

 reached in the correlations, but as far as the Apalachicola section itself 

 is concerned, we believe it now rests upon a solid foundation. 



Apalachicola Section. Correlatives. 



Aluminous clay Pascagoula clays (?) 



Chesapeake marl Chesapeake of Virginia and Maryland. 



f Hattiesburg phase of Grand Gulf beds. 



t Oak Grove sand. 



/ Roberts, Alabama, sand. 



\ Bainbridge residual beds, Georgia. 



r Bainbridge, Georgia, residual beds. 



< Altamaha grits. 



[ Ellisville phase. Grand Gulf (?) 

 L r Typical Grand Gulf 



\ Hawthorne beds of Georgia and Florida. 

 Vicksburg Eocene Vicksburg Eocene. 



Alum bluflt beds n^ 



Chipola marl ^ 



O 

 ITppei: Chattahoochee beds '^ 



Lower Chattahoochee beds ^ 



The total thickness of this Miocene will hardly exceed 200 feet along 

 the Apalachicola river. 



