--> ABSTRACT: Depositional History of Sunniland Limestone (Lower Cretaceous), Raccoon Point Field, Collier County, Florida, by James A. Richards; #91036 (2010)

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Depositional History of Sunniland Limestone (Lower Cretaceous), Raccoon Point Field, Collier County, Florida

James A. Richards

The Sunniland Limestone (Lower Cretaceous), consisting of carbonate rock and anhydrite, bears the only oil and gas production in southern Florida. Raccoon Point field, Collier County, Florida, is one of 13 fields discovered along the Sunniland producing trend, producing from paleotopographic highs associated with shelfal patch reefs and high-energy bioclastic deposits.

Deposition of the Sunniland Limestone, as determined from detailed stratigraphic and microfacies analysis (using core, thin sections, and well logs), occurred in three transgressive-regressive packages or sequences: the lower, middle, and upper Sunniland. Each sequence is further divided into successive shallowing-upward intervals or parasequences. The end of each sequence is marked by an interpreted basinward shift in coastal onlap, representing a major fall in relative sea level. The end of the middle Sunniland is marked by a prolonged drop in relative sea level. During this lowstand a restricted basin developed within the Florida Embayment where a thick subtidal anhydrite was deposited. The drop in relative sea level at the end of the middle Sunniland and the dominance of intertida -flat and supratidal-sabkha environments in the upper Sunniland are interpreted to have greatly influenced reservoir development at Raccoon Point field.

The dolomite reservoirs at Raccoon Point field occur at the top of the middle Sunniland and within the upper Sunniland. They are interpreted as high-energy deposits formed from bioclastic debris and as a network between rudist mounds. Reservoir development in the middle Sunniland is most likely due to the diagenesis associated with restrictive hypersaline conditions and subaerial exposure when sea level dropped at the end of middle Sunniland deposition. Creation of upper Sunniland reservoir was probably influenced by diagenetic fluids derived from the restricted conditions associated with intertidal-flat and supratidal-sabkha environments, in which the overlying sediments were deposited. Anhydrite and dolomitized carbonate rock from these environments dominate the upper Sunniland and orm the overall top seal.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.