Reasessment of Tectonic Style and Crustal Character in Foundation of South Florida and Western Florida Shelf: ABSTRACT

Abstract

Interpretation of seismic reflection data forces a number of constraints on their initial working hypothesis regarding the nature of the crust beneath the Western Florida Shelf. Rather than blocks of pre-Mesozoic continental crust separated by zones of extension or spreading underlain by extensively refitted, transitional, or Jurassic oceanic crust, seismic and well data indicate a vast expanse of paleozoic rock that essentially underlies the entire platform north of 26/degrees/N. Highs and lows (arches and basins) within this region do exist, but both positive and negative areas appear to be underlain by substantial thicknesses of predominantly sedimentary or metasedimentary Paleozoic rocks. It follows that if any oceanic crust is present in the foundation of the Western Florida Shelf, it must be Paleozoic or older in age and must lie below the depth of penetration of their 8-sec records. Rift-style faulting of pre-Jurassic rocks is most common in the Apalachicola basin and northern part of the Middle Ground arch. This style of faulting, consisting of half graben formation, is not restricted to basinal settings nor to Late Triassic-Early Jurassic age of formation. One of the best examples seen on their records appears to be Paleozoic in age. However, enough of the faultmore » activity is identified as Late Triassic to Early Jurassic to justify the inference that this region was involved in the initiation of the Atlantic-Gulf sea-floor spreading event.« less