THE ROCK BLUFF SECTION. 155 



The section here was taken at the highest part of the bluff rising from 

 the river and about midway between the two ends. 



There is below low-water level probably 10 or 12 feet more of the 

 Chattahoochee limestone, worn vertically or nearly so by the action of 

 the current. 



Ocheesee. — About three miles below Aspalaga, on the opposite side of 

 the river (right bank), is Ocheesee landing, marked by several buildings, 

 one of which was once a fine large frame house built on piers. The 

 lower floor was apparently nearly twenty feet above the level of the 

 water at the time of our visit, yet we were told that skiffs had been pad- 

 dled in at the front door and out the back door, through the central hall, 

 during one of the freshets. As the land is very level and not high 

 within sight of the river, it would seem as if an incalculable amount of 

 water would be required to raise the level to the height mentioned. 



Rock Bluff and Section. — Below Ocheesee is a long stretch of river nearly 

 straight, known as " Seven-mile reach," On the left bank, about two 

 miles below Ocheesee, in township 2 north, range 7 west, section 19, 

 rises Rock bluff", the f^ice of the third principal anticline cut by the river 

 below the Florida line. It creates a slight bend and off'ers an excellent, 

 clean section. The settlement named Rock Bluff is four or five miles 

 inland from the river-bank, and should not be confounded with the 

 landing. 



The lower part of the bluff" formed by the Chattahoochee limestone 

 is vertical, rising twelve feet above the water, and presumably nearly as 

 much below it, at low stages of the river. Above this is a mass of marl 

 varying from bluish green to gray in color, weathering white, more are- 

 naceous Ijelow and more marly above, replete with oyster-shells, a fine, 

 large Anomia, a pecten, like young madisonius (but, as observed by 

 Foerste, onl}^ four-sevenths the size of that species ; it is really a Chipola 

 species) ; a Tttrritella and many Balani This assemblage of species in- 

 dicates a shallow water oyster-reef fauna, unquestionably belonging to 

 the old Miocene and forming the shoal-water equivalent of the Chipola 

 and Alum bluff beds, especially the latter. Above this marl lie the red 

 Lafayette clays and gravels — in this case worked-over materials — vari- 

 able in thickness, owing to denudation, but apparently averaging about 

 fifteen feet, and covered with a thin layer of superficial soil and sand. 

 This section was carefully measured with a steel tapeline, due allowance 

 being made for the inclination of the tape from the vertical. It shows 

 the finest and thickest section of the greenish marl exposed anywhere 

 on the river. The contact of the marl with the Chattahoochee limestone 

 is distinct and without apparent unconformity or transition beds of any 

 kind. 



XXI— Bull. Geol. Soc. Am., Vol. 5, 1893. 



