26 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
the material indicates conflicting currents such as occur in shallow 
water or in deltas formed at the mouth of streams, or in the fan-like 
deltas formed by streams on land. The character of the material, 
including quartzitic fragments, quartz sand, mica, and probably 
originally feldspar, indicates the original source as the granitic 
rocks of the Appalachian Mountains, although possibly several 
times reworked in the course of their removal to the present loca¬ 
tion. 
The age of the deposits is difficult to establish owing to the 
absence of fossils. On the Apalachicola River these deposits are 
found overlying both the Oligocene and the Miocene, thus fixing 
their age as later than Miocene. 
On the other hand, the considerable amount of erosion and dis¬ 
integration that has occurred since the material was accumulated 
implies a lapse of time that reaches back well into the Pleistocene 
if not into the Pliocene age. The disintegration that the deposits 
have undergone includes the formation of the surface accumulation 
of the loose residual sand representing complete decay; the forma¬ 
tion of the red loams representing an advanced stage of decay; the 
blotched sandy clays representing partial decay, and the formation 
of the kaolin or ball clay, representing incipient decay affecting the 
least stable of the minerals. The length of time required for this 
amount of disintegration is difficult to estimate. Merrill states,* 
on the authority of Lindgren, that Pliocene andesites in the Sierra 
Nevadas in California are in places decomposed to a depth of 20 feet, 
and adds further, that the region is one of heavy annual precipita¬ 
tion, the rainfall being limited almost wholly to the winter season. 
The climate in Florida is warm and moist, and the rainfall heavy, 
amounting to about 53 inches annually, more than one-half of which 
falls during the three summer months. 
The erosion that has taken place since these deposits were formed 
is extensive and affords a more satisfactory standard of measure¬ 
ment. This erosion is evidenced in the development of stream chan¬ 
nels by surface erosion and the formation of valleys and lake basins 
by underground solution. In many of the limestone sections these 
deposits have become completely disintegrated, remaining merely 
as a residue intermixed with other materials. This condition is 
seen over large areas of peninsular Florida, including the limestone 
and the hard rock phosphate producing part of the peninsula. The 
lake basins of the lake region are believed, as shown in a previous 
paper, to result from underground solution. The sink holes in the 
*Rocks, Rock-Weathering and Soils, p. 262. 
