Facies and Provenance of Basal Clastics in the Eastern Gulf of Mexico

Abstract

The South Florida Basin (SFB) half-graben is one of several basins along the western margin of Florida that formed during initial opening of the Eastern Gulf of Mexico (EGOM), which may have served as sediment pathways for large volumes of clastic influx in to the EGOM. The basal clastic section of the middle Jurassic Wood River Formation overlies Paleozoic basement in the SFB, and records initial syn-rift clastic sedimentation into the South Florida Basin following the breakup of Pangea in the Jurassic. Eighteen well logs that penetrate the Wood River Formation were studied in order to characterize the major facies of the Wood River Formation in the South Florida basin. Four major lithofacies were identified: microcrystalline dolomitic limestone with anhydrite, sandy shale red beds, red shales, and well sorted sandstone. The Wood River Formation consist of a basal clastic section that is generally 100 to 300 feet thick, which is overlain by an upward coarsening succession of alternating sand/shale sequences. Upsection, the Wood River typically coarsens from a shale to sandstone, followed by a gradual transition into a dolomitic limestone. Based on facies and cutting descriptions, the depositional environment of the Wood River has been interpreted as a marine sabkha shoreline. In addition, preliminary detrital zircon provenance analysis of Triassic syn-rift graben-fill clastics of the northen EGOM in the Tallahassee Graben and South Georgia Basin has been conducted to compare with provenance results from the gas bearing Upper Jurrasic Norphlet Formation in the EGOM region. Triassic syn-rift graben-fill clastics contain a mix of 500-700 Ma zircon likely derived from rocks of the Suwannee terrane, and 900-1300 Ma zircon derived from erosion Laurentian Grenville rocks. Detrital zircon ages from the Tallahassee Graben are similar to detrital zircon ages reported for Norphlet Formation in the Destin Dome lease block, which contains a mix of Grenville and Suwannee sources. It is therefore possible that Norphlet Formation clastics in the Destin Dome area were derived from a similar source area as clastics in the Tallahassee Graben. Further studies will compare zircon signatures of the Wood River in the SFB and Norphlet to establish a possible connection. Results from this study may expand the known extent of the Norphlet reservoir, characterize the reservoir potential of the Wood River, and establish a possible sediment pathway between the two formations.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016