SECOND ANNUAL REPORT—STRUCTURE OF FLORIDA. 
49 
below the surface north of Live Oak and Lake City and the forma¬ 
tions comprising the Apalachicola group appear in the valley of the 
Suwanee River. The southern end of the arch sinks gently beneath 
the younger formations so that the limestones of the Vicksburg group 
lie several hundred feet below the surface in Lee County and at Key 
West, where they were encountered in drilling wells. 
The varying depths to rocks of Oligocene age along the east coast 
of Florida are probably due, in part, to local variations in the rate of 
dip and to various minor folds. There appears to be little doubt that 
any upheaval which produced the broad arch which forms the penin¬ 
sula of Florida would also produce minor arches or folds parallel to 
the direction of the main uplift, as well as minor folds transverse to 
the main arch. The satisfactory discrimination of these minor folds 
calls for a large amount of detailed stratigraphic work based upon a 
knowledge of the fossils representing different horizons. It is possible 
that the ridges mentioned by Dr. Dali are really minor folds, but he 
does not appear to have eliminated the possibility of their being due 
to circumdenudation. That there are many minor folds in Florida 
cannot be denied. Good examples of such folds are those which Dali 1 
mentioned on the Caloosahatchee River. These small folds are not 
more than ten to twelve feet in height and are usually not more than 
one-quarter of a mile wide. They are of more than usual interest be¬ 
cause they involve marls of Pliocene age and hence are probably of 
Pleistocene or even of Recent age . 2 
1 Dali, Wm. H., Notes on the geology of Florida. Am. Jour. Sci., 3d series, 
vol. 34, 1887, p. 168. 
Dali, Wm. H., Tertiary fauna of Florida. Trans. Wag. Free Inst, of Sci., 
vol. 3, pt. 6, 1903, p. 1604. 
Dali, Wm. H., Neocene of North America, Bull. U. S. Geol. Survey No. 84, 
1892, p. 143. 
2 For evidence of minor folds in the Chattahoochee limestone and in the 
Alum Bluff formation, see paper on “Fuller’s Earth Deposits,” by E. H. Sellards 
and Herman Gunter (pp. 277-284). 
