SEISMIC STRATIGRAPHIC FRAMEWORK AND FLUVIAL PALEO-VALLEYS OF THE NORTH CAROLINA COASTAL SYSTEM

High resolution, single-channel seismic data are being used to define the seismic stratigraphic framework of Albemarle and Pamlico Sounds, adjacent tributaries, and inner continental shelf of North Carolina. These data reveal the regional geologic framework, distribution and character of Pliocene and Quaternary depositional sequences and associated highly complex incised paleo-drainage systems.

Albemarle Embayment (AE) is a structural basin constrained by the Norfolk Arch to the north and the Miocene Cape Lookout High to the south. During the latest Quaternary, the AE has been constrained by a relict interstream divide to the east, now occupied by the Outer Banks barrier islands. The paleotopography on top of the Miocene is mappable in seismic data and appears to exert a structural control on the modern geomorphology of the relict drainages and associated estuarine system. Pliocene and Quaternary sequences dip and thicken toward the center of the basin, beneath northern Pamlico Sound. At the southern end of Pamlico Sound, the sequences thin onto a Pliocene(?) antecedent high. At least fifteen seismic sequences can be defined within the Quaternary section alone. Sequence boundaries and flooding surfaces are being mapped to provide a three-dimensional perspective on the evolution of the basin fill. Correlation of seismic sequences is complicated by numerous complex fluvial valley incisions that occur in association with sequence boundaries. The incised valleys correspond to the Roanoke, Pamlico Creek, Tar, and Neuse paleo-drainage systems. The paleo-Roanoke River Valley Complex (PRVC) is a late Pleistocene to Holocene valley incised to approximately 35 m below present sea-level in Albemarle Sound, and is approximately 9 km wide. The PRVC meanders to the east, passing beneath the northern Outer Banks at Kitty Hawk. Seismic data from Pamlico Sound show multiple large (30 m deep, 2 to 4 km wide) incised valleys and smaller incised channels within the Quaternary section. The paleo-Pamlico Creek exhibits a dendritic, meandering pattern that drains to the southwest and is bounded to the east by the Outer Banks relict interstream divide. The paleo-Tar and Neuse river valleys trend to the southeast. These valleys merge with the Pamlico Creek valley in a major confluence beneath Ocracoke Inlet and northern Core Banks.