ABSTRACT: Evolution of the Blake Plateau Basin from Rift Basin to Carbonate Platform to Present Eroded Continental Borderland

W. P. Dillon, P. A. Battuello, C. W. Poag, K. O. Klitgord, A. M. Trehu

Multichannel seismic profiles, well and submersible diver samples, and GLORIA long-range sonar data disclose the evolution of the Blake Plateau Basin (BPB) off the southeastern United States The BPB contains strata more than 16 km thick and is roughly 350 km wide. At the postrift unconformity, the northern and western sides of the basin are relatively steep, whereas the southern and eastern sides slope more gently. The entire region probably was a shallow-water carbonate platform during most of the Late Jurassic and Early Cretaceous; the depocenters of the BPB slowly migrated westward during this period, probably due to thermal or magmatic variations in the lithosphere. Although subsidence slowed during the Late Cretaceous, carbonate deposition failed to maintain the surf ce near sea level, and chalks and marls blanketed the sinking platform. During the Cenozoic, the Gulf Stream scoured the top of the present plateau and restricted clastic deposition to the westernmost part of the BPB region, where a narrow shelf is formed. Southerly deep-water thermohaline currents have eroded the old continental slope/reef front into a steep escarpment except for an area having relict canyons. Deep-water erosional retreat of platform deposits forms steep, smooth, or stepped cliffs east of the northern and central BPB; but to the south, erosional cliff retreat occurs by collapse of huge (<10 km) blocks, probably initiated by faults that bound the south side of the BPB. These faults may be reactivated due to differential loading caused by growth of the Bahama platform. /P>

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990