A Sequence Stratigraphic Framework for the Lower Cretaceous North Carolina Coastal Plain, Southeastern U.S.A

Sunde, Richard¹, Brian P. Coffey² (1) Simon Fraser University, Burnaby, BC (2) Simon Fraser University, Vancouver

A lithology-based sequence stratigraphic framework for the little studied Lower Cretaceous mixed carbonate-siliciclastic sediments of the subsurface Albemarle Basin is presented. Thin sections produced of well cuttings from exploration wells were analyzed to characterize lithology, fossil components, depositional facies, and diagenetic events, because the study interval is entirely confined to the deep subsurface in a basin lacking core control. Data was then used in conjunction with wireline logs to document the facies abundance and stacking patterns. Integration of 2D seismic data and biostratigraphic control allowed regional correlation of major transgressive-regressive events between wells, resulting in the generation of a sequence stratigraphic framework for the onshore basin.

Results show the following dominant lithofacies (listed from shallow to deep): sandstone, skeletal sandstone; variably sandy mollusk packstone/grainstone; siltstone; unfossiliferous and diatomaceous shales; skeletal wackestone; variably sandy (quartz and glaucony) lime mudstone, and marl.

Comparison of observed facies with cores and wireline logs from the Baltimore Canyon and S.E. Georgia Embayment confirms the sequences consist of upward shoaling siliciclastic shorefaces, with basal open shelf mollusk-rich carbonates often marking transgressive events. Basin-scale depositional trends indicate greater accumulation of the carbonate facies in the southern basin, with increased fine siliciclastic material to the north. This trend may reflect a major siliciclastic point-source in the vicinity of the ancestral Chesapeake region.

The depositional and diagenetic models generated from this research provide valuable insight into the facies and reservoir properties in coeval offshore units comprising frontier exploration targets along the Atlantic coast of the U.S. and Canada.