Foerste — Eocene and Miocene of Georgia and Florida. 41 



Aet. VIII. — The Upper Vicksburg Eocene and the Chatta- 

 hoochee Miocene of Southwest Georgia and adjacent Florida ; 

 by Aug. F. Foekste. 



The Boundary Line between the Vicksburg Eocene and Chatta- 

 hoochee Miocene in S. W. Georgia. 



The chief topographical feature of southwestern Georgia 

 is the line of demarcation between the Eocene lowlands and 

 the margin of the Miocene red clay plateau.* This line enters 

 the State about 5 miles north of its southwest angle, follows 

 the bluffs along the southern side of the Flint River for about 

 12 miles, continues in its direction across the country as far 

 as Roseland Plantation, 1 miles south of Bainbridge, passes 

 immediately to the north of Gasteropod Gully, Glenn's Well, 

 and Powell's Limesink, the last locality being about 10 

 miles east of Bainbridge on the Thomasville road, and then 

 turns more strongly toward the northeast, so as to leave the 

 limesink and the Barrows plantation coral locality on the right. 

 From its western extremity to Roseland Plantation this line is 

 quite direct ; it may be easily followed as far as Powell's lime- 

 sink ; beyond that point it seems to become more crooked and 

 has so far not been accurately determined. 



Method of Exposure of the Vicksburg. 



On the northern margin of the red clay plateau the Vicks- 

 burg is found in limesinks, underlying the Chattahoochee, or 

 Lower Miocene. In the lowlands extending from the plateau 

 to the Flint River it occurs in the bottom of wells. Away 

 from the river, very few surface exposures, which are evidently 

 in situ, occur. Along the Flint River large blocks of siliceous 

 Vicksburg rock are fairly abundant but it is evident that the 

 greater part are only residual remains of the Vicksburg ; the 

 softer limestones and marls have disappeared or gone over into 

 red clays, and in most places only the broken fragments of the 

 silicified beds remain, let down as huge bowlders and slabs to 

 the present limit of degradation, — the lower levels of the river 

 banks. 



At first it seemed impossible to use these blocks for strati- 

 graphical purposes. However, during a trip down the Flint 

 River, with Prof. Raphael Pumpelly, the localities where the 

 bowlders occur were carefully platted on a sketch map of the 

 river, and it became evident that these bowlders were distrib- 



* That part of the plateau region lying south of Bainbridge is more fully de- 

 scribed by Prof. Raphael Pumpelly, in this Journal, Dec., 1893, page 445. 



