Basement Structure of Florida and its Tectonic Implications

ABSTRACT Geologic data from nearly eighty recent wells in Florida and Georgia permit substantial refinement of earlier interpretations of Florida basement structure. Upper Jurassic, Cretaceous, and Tertiary sediments in Florida onlap the eroded surface of a basement complex which varies from Precambrian to Jurassic in age. As determined by previous workers, the main structural feature underlying Florida is the Peninsular Arch. This is a large Precambrian block covered by Paleozoic sediments. A similar, smaller crustal block, centering on Jackson County, occupies the Florida panhandle. In both blocks, Ordovician to Devonian clastic rocks overlie a deeply truncated Precambrian complex which was affected by Cambrian igneous intrusion. The Paleozoic rocks were subjected to Late Paleozoic uplift with some volcanic activity followed by uplift with tilting, block faulting and post-orogenic igneous intrusion during the Triassic Period. The new data presented here clarify the succession and areal distribution of some of the volcanic and hypabyssal rocks, showing that Jurassic basalt flows covered the Peninsular arch below the 28°N parallel. The entire Florida portion of the Florida-Bahama platform probably represents crust which has been continental through Phanerozoic time. Subsurface data from Florida do not support the more speculative hypotheses about the history of the Florida-Bahama Platform and the Gulf of Mexico region. Published and new geologic data are consistent with responsible attempts to reconstruct the history of the Gulf of Mexico region by rifting during the opening of the North Atlantic Ocean basin. This agreement so far represents circumstantial evidence for the operation of plate tectonic mechanisms rather than direct, conclusive proof. The evidence, such as it is, favors the hypothesis outlined by Freeland and Dietz (1972). The circumstantial nature of evidence for the former activity of place tectonic mechanisms in Florida need not hinder the application of new tectonic theories to petroleum exploration in Mesozoic rocks of the Florida-Bahama region and the outer continental shelf of the Atlantic coast.