| Summary |
Seismic and core analysis of the Roanoke Island area. Dare County, North Carolina have revealed a complex late Quaternary stratigraphy. The over-all stratigraphy and time relationships of the stratigraphy were acquired by analyzing 1) 585 km of 7kHz acoustic sub-bottom profiles, 2) 100 km of high resolution Uniboom seismic sub-bottom profiles, 3) 59 vibra-cores, 4) 37 rotary-drill cores, and 5) over 100 carbon-14 age dates from material in cores. Seismic profiles reveal a highly channeled sub-surface throughout the study area. Most shallow channels within the estuaries are Holocene in age while deeper inshore and offshore sub-surface channels are Pleistocene in age except for offshore channels of the Albemarle system which is Holocene. The channels were formed during episodes of emergence of the area and subsequently infilled with sediment during the following transgression over the area. The general stratigraphy consists of a repetitive series of low angle, eastward dipping, imbricate, barrier island sand sheets with associated facies; these sand sheets rest atop an earlier widespread marine unit. The stratigraphic units have been divided into five depositional sequences. The first is the basal nearshore marine facies. The remaining four sequences are barrier island-estuarine systems consisting of one or more of the following facies; (1) nearshore marine facies, (2) barrier island facies, (3) back-barrier estuarine facies, (4) inlet channel facies, (5) filled lateral estuary facies, (6) filled trunk stream facies, and (7) peat facies. Each depositional sequence is the result of eustatic sea-level fluctuations; each sequence was deposited during a transgressive cycle and eroded and reworked during the subsequent regression. The transgressive maximum for each depositional sequence is marked by the westernmost position of the barrier island facies. The resulting barrier ridges may be correlatable to similar barrier island ridge systems in southeast Virginia. All but the last of the depositional sequences are late Pleistocene in age. The last and present depositional sequence is a product of the Holocene and Recent transgressive cycle. |
