Correlation of key seismic reflectors with the lithlogic, biostratigraphic, and paleobathymetric logs of the Chevron COST B-3 well shows that this part of the Atlantic continental slope changed from a platform-fringed shelf in the Middle to Late Jurassic and Early Cretaceous to a deep-water slope in the Late Cretaceous and early Tertiary. Closely matching paleobathymetric and eustatic sea-level cycles indicate that sea-level fluctuations strongly regulated deposition by cyclically shifting the loci of deposition among the shelf, slope, and rise. At the same time, the alternate loading and unloading of the shelf may have accentuated the relative change in sea-level by producing corresponding cycles of isostatic subsidence and rebound.

Some major seismic reflectors beneath the shelf appear to coincide with erosional disconformities formed during early Oligocene, early Paleogene, early Turonian, and early Barremian. Reflectors of Late Cretaceous through early Tertiary age are continuous from the present shelf to beneath the present rise; their continuity, seismic character, and structural geometry support the idea that the margin was broadly constructional during this interval and that the shelf break was poorly defined. Beneath the rise, reflectors are mainly conformable; their character suggests onlapping fill and slope-front fill facies. Broad downslope channels were cut during the middle Tertiary and late Quaternary presumably in response to major drops in sea level.

End_of_Article - Last_Page 781------------