Stratigraphy and Depositional History of Baltimore Canyon Trough, Mid-Atlantic OCS: ABSTRACT

Abstract

Examination of exploration wells, COST wells, and CDP reflection seismic lines reveals many details of the stratigraphy and depositional history of the Baltimore Canyon Trough. Two stratigraphic test wells penetrated about 1,500 m of Cenozoic sediments, 900 m of Upper Cretaceous strata, 1,200 m of Lower Cretaceous strata, and bottomed in Upper Jurassic beds at depths greater than 4,850 m. Criteria used in determining depositional environments of strata include lithology and texture (from electric logs, cuttings, and cores) as well as facies relations and biologic indicators. Seismic stratigraphy and correlations with other basins indicate that Upper Triassic-Lower Jurassic basal strata probably include red beds with basalt flows, dolomite, anhydrite, and salt deposited in arid continental and supratidal sabkha environments. Progradation of carbonates during a Middle-Late Jurassic marine transgression resulted in the formation of reefs and banks on the shelf edge which grade shoreward to terrigenous deposits overlain by limestone on the shelf. During the Early Cretaceous, prograding deltaic wedges built the shelf seaward and covered it with a thick blanket of sandstone and shale. Marine influence gradually increased, and the end of the Early Cretaceous is marked by a broad, thick, nearshore sandstone (Albian-Cenomanian). The transgression continued into the Late Cretaceous as worldwide sea level reached a maximum. Calcareous sheet sands, mudstone, and limestone were deposited across the continental shelf and slope and spilled into the ocean basin. Regional unconformities characterize the Turonian, the Tertiary-Cretaceous boundary, the lower Oligocene, and lower Miocene strata. The Cenozoic sequence of limestone, shale, and sand represents progressively shallower waters. End_of_Article - Last_Page 1658------------