--> ABSTRACT: Rebecca Shoal Barrier Reef Complex of Gulfian and Paleocene Age--Onshore and Offshore Florida, by George O. Winston; #91022 (1989)
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Previous HitRebeccaNext Hit Shoal Barrier Reef Complex of Gulfian and Paleocene Age--Onshore and Offshore Florida

George O. Winston

Surrounding the Florida Peninsula and the offshore portion of the South Florida basin is a 1,300-mi long dolomite barrier reef complex that occupies a 3,800-ft composite interval spanning most of the Gulfian and Paleocene. Forty-four wells have penetrated various aspects of this complex.

Growth began with the Card Sound facies (some 1,400 ft thick) in the lower Gulfian, shortly after the end of the Early Cretaceous. This facies is present in only two wells, 4 mi apart on Key Largo.

The appearance of the Previous HitRebeccaNext Hit Shoal reef in the earliest Gulfian indicates that the Florida Straits were then present, as deep water would have been necessary to support a growing reef of this magnitude.

During the late Gulfian, the reef (Plantation equivalent) expanded northward along the East Coast and westward along the Keys. The width now was over 6 mi. By the beginning of the Paleocene, the reef (Tavernier facies) had completely surrounded the peninsula, resulting in the deposition of the Cedar Keys dolomite-anhydrite lagoonal facies. The width of the complex was now as much as 20 mi.

At the close of the Paleocene, the Previous HitRebeccaTop Shoal reef ended abruptly. It was overlain by an orange/brown anhedral dolomite characteristic of the basal Eocene.

The lithology of the outer region of the reef complex is characterized by a light-colored, porous, fine to medium crystalline euhedral dolomite. Large cavities, including a 60-ft cavern, have been reported. Two core samples show a taluslike rubble texture with vug porosity between the square-sided fragments.

Behind the Tavernier reef, this facies is gradually replaced by nonporous anhedral and cryptocrystalline dolomite. Father lagoonward, these three lithologies become interbedded with typical Cedar Keys, a very fine microcrystalline to microcrystalline dolomite.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.