Sequence Stratigraphy of Lower Cretaceous Mixed Carbonate-Siliciclastic Passive Margin Sediments, Southeastern U.S.A.

Richard F. Sunde¹ and Brian P. Coffey^2
1 Simon Fraser University, Burnaby, BC
² Exxon-Mobil, Houston, TX

A lithology-based sequence stratigraphic framework for the Lower Cretaceous mixed carbonate-siliciclastic sediments of the subsurface North Carolina coastal plain is being generated using well cuttings from selected hydrocarbon exploration wells. Stained thin-sections produced from cuttings with abundant carbonate material were analysed using petrographic methods to better characterize fossil components, facies, lithologies, and cements. This data was then used in conjunction with wireline logs to document the facies abundance, stacking patterns, and diagenetic events of the little studied Albemarle Basin. Correlation between wells was aided by the use of public domain seismic data sets and published biostratigraphic studies. Additional biostratigraphic and strontium isotopic analyses are being conducted. Preliminary results from Marshall Collins no.1 well (DR-OT-3-65) indicate the following dominant lithofacies (listed in an approximate basin ward position of deposition): sandstone, skeletal sandstone; siltstone; unfossiliferous and diatomaceous shales; skeletal wackestone; sandy and sand-free mollusk-dominated skeletal packstone/grainstone; variably sandy (quartz and glauconite) lime mudstone, and marl. Comparison of observed facies with cores and wireline logs from the Baltimore Canyon and S.E. Georgia Embayment suggest the sequences consist of upward shallowing siliciclastic shorefaces, with down shelf mollusk rich carbonate build-ups.

Results of the study will be compared with reference sections from the U.S. Gulf coast, Western Europe, Georges Bank, and emerging data from the Scotian Shelf. The depositional and diagenetic models generated from this research provide valuable insight into the distribution of potential hydrocarbon reservoir facies along frontier exploration areas offshore of the Atlantic coast of the U.S. and Canada.