munication, A.L. Odom and R. Taylor, Sohio, 1986). An alternative data interpretation suggests that the aforementioned Triassic section is Paleozoic (G. Winston, personal communication, 1988).
The Apalachicola Embayment and smaller north Florida basins are successor basins within the Suwannee basin (Figure 12). On a more regional scale, the Apalachicola Embayment is the southwest extension of the larger South Georgia basin (Chowns and Williams, 1983). The eastern portion of the South Georgia basin consists of the Southeast Georgia Embayment. These two embayments are separated by the Suwannee Saddle, which is a northwestern extension of the Peninsular Arch. The Peninsular Arch is a positive feature containing upper Precambrian-Lower Cambrian continental crust overlain by Suwannee basin sediments. Intrusions of Mesozoic diabase as well as basalt flows are located within the Suwannee Basin sediments.
The southeastern subcrop limit of the Suwannee basin is bounded by a central Florida igneous complex. Barnett (1975) has subdivided the igneous terrane into a northern felsic volcanic and southern felsic to intermediate plutonic province, the latter of which is termed the Osceola Granite (Chowns and Williams, 1983). Radiometric data indicate that the Osceola Granite is Middle Cambrian in age (approx. 527 Ma, Bass, 1969; 527-534 Ma, Dallmeyer et al., 1987). Both Chowns and Williams (1983) and Dallmeyer et al. (1987) propose that these older crystalline basement rocks are part of the Pan-African Rokelide fold belt. A core from St. Lucie County (Figure 1, corehole location number 31), south of the Osceola Granite, is reported to contain Pan-African metamorphic rocks overlain by a felsic igneous sequence and Mesozoic (?) basalt (Bass, 1969; Chowns and Williams, 1983). Bass (1969) reports an approximate age of 530 Ma (Rb-Sr, biotite) for dioritic gneiss in this core.
The South Florida basin shown on Figure 12 is a Mesozoic stratigraphically defined basin centered in the Gulf of Mexico. The portion of the basin located on Peninsular Florida is approximately the northeastern third of the entire basin. Within this portion of the basin, Jurassic and younger sediments overlie a predominantly mafic volcanic basement (Winston, 1971; Barnett, 1975). Cuttings from a deep oil test well in Collier County (Exxon, W-15095, P-1042), however, reveal felsic igneous rock directly below the top of the basement surface at the depth of approximately 17,000 feet. An unpublished K-Ar, whole rock age determination from the cuttings suggests Middle Jurassic emplacement (164 + 7 Ma, Amoco, 1985). Also in Collier County, a "rhyolite porphyry" in Bass well No. 12-2 (W-12838, P-778) has been dated at 189 + 5 Ma (Rb-Sr whole rock, Shell Oil, 1978). Radiometric dating of basalts in the basin indicates that their emplacement was during the Early to Middle Jurassic (Table 1). Note, however, that caution should be used when interpreting any of these data (see "Age" section in Part One of this report).
Since the early comprehensive works of Applin (1951) and Barnett (1975), numerous studies have focused on geophysical, radiometric, paleontologic, petrologic and tectonic aspects of the deep subsurface of Florida. Although new data and theories arise, several unanswered questions and occasional conflicting interpretations still exist. Additional work in all of the above disciplines is needed in order to further refine our knowledge of the Florida Basement.
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