Abstract: Stratigraphic Synthesis and Hydrocarbon Potential of Central North Atlantic Mesozoic

L. Jansa

The Mesozoic sedimentary sequences of the western and east-central North Atlantic basin have very similar ages, faunal assemblages, and petrographic composition, even though they are separated by the volcanic rocks of the Mid-Atlantic Ridge. Seven sedimentary formations can be recognized in the central North Atlantic basin. In ascending order, they are: Cat Gap Formation (Oxfordian greenish-gray limestones), Cape Verde Formation (Oxfordian-Kimmeridgian reddish-brown argillaceous limestones), Maio Formation (Portlandian-Hauterivian light-gray chalks), Hatteras Formation (Aptian-Cenomanian black bituminous shales and marls), Dacia Formation (Valanginian-Albian greenish-gray claystones with intraclast turbidites), Boa Vista Formation (Upper Cretaceous greenish claystones), and Bermuda Rise Formation (upper Cenomanian-Maestrichtian to Paleocene varicolored zeolitic clays).

The oldest sediments were deposited in an epibathyal environment, above carbonate compensation depth (CCD). The sea bottom subsided below the CCD in Aptian time.

As to the hydrocarbon potential of the Atlantic basin Mesozoic, even though good source rock for hydrocarbon generation is present in black bituminous shales of the Hatteras Formation, the basinal and lower rise deposits, as indicated by results of the Deep Sea Drilling Project in the central North Atlantic basin, lack reservoir rocks. Other negative factors are low to moderate depositional rates, lateral sediment dispersal, bioturbation, lack of tectonic activity, and early diagenetic to epigenetic cementation of turbidite beds. The probability of major hydrocarbon accumulations in the basinal part and continental rise of the central North Atlantic (excluding gas clathrates) thus is thought to be minimal.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC