THE SOILS OF FLORIDA. 
13 
although variable is prevailingly an impure clayey limestone. As a 
rule strata of an impure limestone alternate with softer and more 
clayey layers, the latter being scarcely other than calcareous clays. 
Upon exposure this stratum weathers in a characteristic manner, 
breaking into octagonal blocks varying from two to six inches in size. 
Further weathering is by exfoliation and crumbling. The final prod¬ 
uct of weathering is a green sticky clay, the calcareous material hav¬ 
ing been largely removed. Numerous excellent exposures of the Chat¬ 
tahoochee formation occur along the Apalachicola River from the 
State line to Rock Bluff. The formation dips to the south and at 
Rock Bluff passes beneath later formations. Some good exposures 
of the Chattahoochee formation are seen on the Chipola River, the 
rapids of the river near Altha, in Calhoun County, being formed by 
this limestone. West of the Chipola River the formation is not 
extensively exposed and the limestone phase of the formation is 
probably not well developed. However, Matson and Clapp* note the 
occurrence of this limestone at Knox Hill, in Walton County, and on 
the Choctawhatchee River, at Caryville, in Washington County. To 
the east of the type exposure the formation comes to the surface at 
several places along the Ocklocknee River. A limestone probably of 
this formation is seen just above the crossing of the Georgia, Florida, 
& Alabama Railway between Tallahassee and Havana, and near the 
crossing of the Seaboard Air Line Railway between Tallahassee and 
Quincy. A similar limestone is very generally seen in the sinks and 
lake basins of the northern half of Leon, Jefferson, and Madison 
Counties. 
Although the limestone disappears by dipping beneath the sur¬ 
face at Rock Bluff on the Apalachicola River, and not far below the 
Seaboard Air Line Railway crossing on the Ocklocknee River, yet 
from this latter point the line of surface exposure bends southeast 
and reaches to the coast in the vicinity of St. Marks. From St. 
Marks east to the Suwannee River a similar limestone is frequently 
exposed or lies near the surface. The channel of the Suwannee 
River, as previously stated, cuts through Upper Oligocene forma¬ 
tions. The distribution of the Chattahoochee Limestone east of the 
Suwannee River has not been determined. 
; 
TAMPA FORMATION. 
The Tampa formation is similar in character to the Chattahoo¬ 
chee, and consists of clayey limestones and clays. The type expo¬ 
sure of the Tampa Limestone is along-Tampa Bay. The silex beds 
*Florida Geological Survey, Second Annual Report, p. 84, 1909. 
