146 Papers from the Marine Biological Laboratory at Tortugas. 



AREAL DISTRIBUTION OF THE GEOLOGIC FORMATIONS. 



This subject may be introduced by reference to the Table of Geologic 

 Formations given on page 126 of this paper and to plate 4. For strati- 

 graphic descriptions the " Preliminary Report on the Geology of Florida" 

 by Messrs. Matson, Clapp, and Sanford l may be consulted. 



OLIGOCENE. 

 VICKSBURG GROUP. 



The rocks belonging to this group, the oldest geologic formation 

 known on the Peninsula, form the surface of the area from Sutherland 

 in the northwest corner of Hillsboro County northward to the vicinity 

 of Newberry and Gainesville. The western boundary is almost on the 

 water front at Sutherland and lies only 5 or 6 miles from the shore of 

 the Gulf from that place to Crystal River, beyond which it curves to the 

 northwest, roughly paralleling the shore at a distance of 6 to 12 miles 

 from it, to 6 miles south of the latitude of Cross City. This boundary 

 is slightly concave toward the west and is separated from the shore of 

 the Gulf by a narrow fringe of Quaternary deposits, ranging from 1 to 12 

 miles in width. The northern boundary of the area is a slightly sinuous 

 line running in an easterly direction from opposite. Pine Point through 

 Old Town, Newberry, just south of Gainesville, to Lockloosa. From 

 the last -mentioned town, the boundary bends southward and passes 

 through Sumterville, whence it extends southwestward to Sutherland. 

 The eastern boundary is strongly convex to the east. North of this 

 main area there are outlying small areas almost as far north as the 

 latitude of Lake City. If the boundaries of the main area were 

 extended so as to include the outliers, they would still retain a con- 

 cavity on the west and a convexity on the east. 



APALACHICOLA GROUP. 



As is implied in the preceding paragraph rocks of the Apalachicola 

 Group are not present between the western boundary of those of the 

 Vicksburg and the Gulf. The rocks of the main Vicksburg area pass 

 beneath the Apalachicola rocks on all sides except on the west, and all 

 outlying areas of the former are surrounded by rocks of the latter group. 

 The Apalachicola rocks continue northward into Georgia where outcrops 

 of the Vicksburg limit their northern extension. They extend to the 

 westward, separated from the coast by a margin of Pleistocene deposits, 

 to the vicinity of the mouth of St. Marks River, where they reach the 

 coast through a stretch of several miles. Thence they extend westward 

 to the Ocklockonee River near Sopchoppy, from which place the bound- 

 ary bends northward, passing west of Tallahassee; there it is sharply 

 flexed to the west and crosses the Apalachicola River at Alum Bluff. 

 Westward of a point 9 to 10 miles west of Tallahassee an area of Miocene 

 (the Choctawhatchee formation) intervenes between the Apalachicola 

 and the coastal fringe of Pleistocene deposits. 



1 Florida Geol. Surv., 2d Ann. Report. 



