An extensive network of high-resolution uniboom subbottom seismic profiles in combination with 9-m vibracores was obtained across the North Carolina continental shelf in Onslow Bay. Resulting data delineate an extremely complex depositional pattern of the Neogene sediments around the east and southeast flank of the Carolina platform. This major broad platform structure trends southeast across the Mid-Atlantic shelf and consists of Paleogene and Cretaceous sediments. The Neogene section, dominated by the Miocene Pungo River Formation, forms a complex clinoform sediment package which dips and thickens eastward and southeastward from the platform margin. This sediment package consists of numerous depositional sequences which are abruptly truncated by erosional surfaces and a sociated channels. Each channeling system was subsequently filled during the following depositional regime. The depositional sequences, which may reflect third- and fourth-order cyclical events, are characterized by interbedded lithologies consisting of phosphorite sands, phosphatic foraminiferal muds, dolosilts, and calcareous quartz sands. Deposition of the Pungo River Formation reflects deposition on a major second-order transgressive cycle. Thus, the upper part was deposited over the edge of the Carolina platform filling numerous erosional channels in the underlying sedimentary units. Postdepositional folding followed by subsequent erosional cycles severely truncated the sediments again. This resulted in a series of flexure basins and channels, filled with Pungo River sediments, lyin on top of the Carolina platform as isolated outliers. The complex depositional erosional patterns of the Pungo River sediments reflect several orders of complex cyclical sedimentation taking place on the continental shelf during the Miocene.

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