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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 12. (December)

First Page: 2571

Last Page: 2593

Title: Stratigraphy and Structure of Southern Blake Plateau, Northern Florida Straits, and Northern Bahama Platform from Multichannel Seismic Reflection Data

Author(s): R. E. Sheridan (2), J. T. Crosby (2), G. M. Bryan (3), P. L. Stoffa (3)


Approximately 2,100 km of 24-fold multichannel seismic reflection data reveal much about the subsurface geology for a large part of the continental margin east of Florida. Discordance between the westward-dipping pre-breakup sediments and the eastward-sloping basement along the edge of the Blake Plateau is interpreted as an effect of a splinter of continental margin derived from the African plate by a spreading-center jump in the Middle Jurassic. Early rifting centered under the main part of the Blake Plateau became inactive, as a spreading-center jump shifted the active rift to east of the present Blake Escarpment along the Blake Spur magnetic anomaly.

In the northern Florida Straits the data reveal that the breakup unconformity, underlain by Triassic-Lower Jurassic(?) arkosic volcaniclastics, extends from southern Florida to the western Bahama Banks. These volcaniclastics are associated with the rift-crust of intermediate nature formed just prior to and during breakup of the North American and African continental plates.

Back-reef platform deposits of limestones, dolomites, and evaporites of Late Jurassic to Albian age extend from the Blake-Bahama Escarpment westward beneath Florida. These deposits formed what once was a megabank extending over a wider area than the present smaller isolated Bahama Banks. The formation of the Florida Straits and Bahama channels occurred during the Cenomanian transgression. Only on the present Bahama Banks and Florida platform did shallow-water carbonate deposition persist to maintain a shallow-bank environment.

Evidence of recurring scour by current erosion is found in the Florida Straits. Erosional events apparently occurred in the middle Cenomanian, middle Paleocene, early-middle Eocene, and Eocene-Oligocene, which coincidentally are times of lower eustatic sea level according to Vail et al (1977a). This evidence of Florida current scour indicates that the current was present as far back as the Cenomanian.

Major faulting appears to have dropped the Northeast Providence Channel relative to the western Bahamas after the Albian. Submarine erosion and bank buildup created the channels and smaller relief features like Great Abaco Knoll beginning in about the Cenomanian.

A carbonate bank margin and reef complex was present along the Bahama Escarpment since the Middle Jurassic. Apparently these organic buildups seeded on originally shallow structural relief on oceanic basement created during the spreading-center jump to the position of the Blake Spur magnetic anomaly. The bank margin apparently has retreated at least 15 km from a Late Jurassic-earliest Cretaceous position now marked by a bench below the Au unconformity.

Active faulting occurred along the Great Abaco fracture zone at least through the Late Cretaceous and perhaps into the Tertiary. These relatively young tectonic events, together with the post-Albian faults in Providence Channel, indicate interactions between the Atlantic and Caribbean plates and that extensions of faulting have taken place far to the northeast of Cuba and the Greater Antilles.

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