Introduction Topo-Eco Divisions Geology - General Features - Miocene Deposits - Pliocene Deposits - Pleistocene Deposits - Recent Deposits - Structural Interpret. - Ground-Water Occurrence > Correlation Studies   -  Logs of wells   -  Fauna in wells References PDF version

Correlation Studies

General Statement

The correlations illustrated in the cross sections (fig. 2, fig. 3) are based chiefly on lithologic similarity of the sediments. Vertical changes in lithology, although usually gradational, take place rapidly. There is almost no horizontal continuity of the beds, which makes exact correlation impracticable. Exposures of all of the formations along and near the western edge of the Everglades are scarce and therefore are of little use in substantiating the correlations.

The section which follows contains the logs of the 43 test wells drilled by the U. S. Engineers. Each test well was drilled to a depth of 30 feet; thus the bottoms of the wells range from 8.5 feet below mean sea level in well 3 in northern Hendry County to 22 feet below mean sea level in well 41 near the Tamiami Canal. Also included is a list of macrofossils collected at various depths throughout the 30-foot core sections. The lists were prepared by F. S. MacNeil of the U. S. Geological Survey. Collections were made wherever a relatively large assemblage occurred; not all core holes are represented because the areal distribution of shelly material was very inconsistent. If diagnostic fossils were noted, then that portion of the section was assigned to the indicated geologic age. Many of the species listed are of long stratigraphic range and were of little use in differentiating formations. Several forms occur in great numbers in both Pliocene and Pleistocene deposits; thus the boundary between the Caloosahatchee marl and the formations of Pleistocene age is usually indefinite unless a lithologic break or an unconformity is evident. Scarcity of these fossil forms in certain assemblages from the lower parts of the holes may be considered negative evidence of Miocene age. Unfortunately, identifiable specimens were not found in the cores in some critical areas. Boundaries between formations are tentative, for the writers believe that other interpretations are possible.