GEOLOGY BETWEEN APALACHICOLA AND OCKLOCKNEE RIVERS. 53 
ford, a distance of 3 miles. On the line of the Georgia, Florida and 
Alabama railway the belt of heavy sands extends from 2 miles south 
of Tallahassee to Wakulla county line, having here a width of 8 or 
9 miles. 
The location and direction of this belt of sand, extending from 
slightly north of west to somewhat south of east, suggests that it 
may represent either a beach deposit or the outcropping of a very 
sandy horizon of the underlying formation. 
Loose surface sands are found in many other places within this 
area under conditions that seem to indicate, that they are residual. In 
many instances the sand has, no doubt, been moved more or less by 
wind or by stream action.* On slopes where surface wash is pro- 
nounced, these loose sands are wanting, as they are removed as rap- 
idly as formed. On the other hand, on level lands the sand often 
accumulates to a considerable depth. 
GEOLOGIC HISTORY. 
The geologic history recorded in this area, as already noted, 
is that from the Oligocene time to the Recent. During the later 
part of Oligocene time, if the Chattahoochee formation is correctly 
referred to that period, this part of Florida as well as parts of 
Georgia, was submerged beneath a sea of moderate depth. The 
deposits that accumulated in this sea, making up the. Chattahoochee 
formation, were chiefly calcareous, although in addition to the cal- 
careous material there was included a very considerable proportion 
of fine clay carried in from the land. Relatively little sand was 
washed into this formation, which indicates either that the shore 
line was some distance away or that the currents were very mild. 
The change in conditions in passing from the. Oligocene to the 
Miocene in this area were gradual. The predominately calcareous 
materials of the Chattahoochee formation give place gradually to 
the sandy calcareous materials of the Alum Bluff formation. Dur- 
ing the period of accumulation of the Alum Bluff formation, lower 
and middle Miocene, the shore line was much nearer. In the type 
* In the railway cut at Lowry, on the Apalachicola Northern Railway, there 
is exposed, about 4 feet below the present 1 surface, an old swamp deposit with 
many tree stumps in place. This swamp had been obliterated by the shifting 
of the sands, and there was on the surface at this place no evidence of a 
swamp, the swamp growth having been replaced by “scrub” vegetation. 
