REINTERPRETATION OF THE PENINSULAR FLORIDA OLIGOCENE - AN INTEGRATED STRATIGRAPHIC APPROACH

A very thick (>300 m) nearly continuous Oligocene section exists in so uthern peninsular Florida, as revealed by lithostratigraphic, biostrat igraphic (mollusks and dinocysts), chronostratigraphic (Sr isotopes) a nd petrographic analyses of twelve cores and two quarries. The Oligoce ne deposits in the subsurface of southern Florida are the thickest doc umented in the southeastern U.S., and they also may represent the most complete record of Oligocene deposition in this region. No major unco nformities within the Oligocene section are detected in the southern p ortion of the peninsula; hiatuses at the Eocene-Oligocene boundary, th e early Oligocene-late Oligocene boundary, and the late Oligocene-Mioc ene boundary, are of limited duration if they exist at all. No signifi cant disconformity is recognized between the Suwannee Limestone and th e Arcadia Formation in southern Florida. However, on the east coast of Florida a hiatus of more than 12 m.y., spanning from at least the mid dle of the early Oligocene to early Miocene is present. The Suwannee L imestone was deposited during the early Oligocene. The top of the Suwa nnee Limestone appears to be diachronous across the platform. The 'Suw annee' Limestone, previously identified incorrectly as a late Oligocen e unit, is herein documented to be early Oligocene and is encompassed in the lower Oligocene Suwannee Limestone. An unnamed limestone, found on the east coast of the peninsula is, at least in part, correlative with the Suwannee Limestone. The Arcadia Formation, basal Hawthorn Gro up, accounts for a large portion of the Oligocene deposition in southe rn Florida, spanning the interval from the middle of the early Oligoce ne to at least the early Miocene. Comparisons of the depositional patt erns, and the distribution of dolomite and phosphate within the Suwann ee Limestone and the Arcadia Formation, suggest fluctuating sea levels and that the paleo-Gulf Stream played a role in determining the natur e and extent of Oligocene deposition in peninsular Florida.