Subsurface Geology of the Pamlico Sound Area, Coastal North Carolina: ABSTRACT

Abstract

The subsurface of the Pamlico Sound area in North Carolina contains the state's thickest drilled succession of Mesozoic-Cenozoic strata. The subsurface geology of approximately 1,800 mi2 of northern Pamlico Sound was investigated using logs and cuttings from seven wells and about 135 mi of multichannel reflection seismic line. Crystalline basement rocks dip about 1.2° east-southeast. The overlying strata, which range in thickness from 5,145 ft (Albemarle Sound area) to 9,860 ft downdip (Cape Hatteras), are not significantly affected by faulting. Jurassic(?) through Eocene sediments all appear to have accumulated within a gently subsiding, marine-shelf environment. Four distinct lithofacies characterize these strata. The basal Unit 1 (La Casitan-Trinitian) reflects a westward transgression of coastal sandstone, outer shelf mud, and carbonate across shallow shelf to lagoonal deposits. Unit 2 (Trinitian-Washitan) is an upward-coarsening detrital sequence which terminates with discontinuous, marine-shelf sandstones that reflect a northerly source. An abrupt transition into marine-shelf mudstones and limest nes marks the base of Unit 3 (Woodbinian-Austinian); these are abruptly overlain by interbedded shelf sandstones that merge to the southwest. Unit 4 (Tayloran-Claibornian), the uppermost interval studied, is characterized by thick, widespread marl, which grades into glauconitic sandstone and finally marine limestone. Continuous seismic reflectors occur at the basement interface and the top of Units 2 and 4. A reflector, possibly a stratigraphic discontinuity, occurs at the top of the Cretaceous in Unit 4. Well-developed prograding seismic sequences occur above Unit 4. End_of_Article - Last_Page 1442------------