305 Stratigraphy (Posters)

Quaternary Stratigraphic Framework of the Eastern Coastal Plain and Outer Banks of North Carolina, USA

Paper number: 305-8
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

The late Pleistocene Quaternary landscape of eastern North Carolina consists of low-relief, flat, eastward dipping marine terraces (ramps) that are dissected by a series of nested paleovalley complexes. In this terrane, the USGS's North Carolina Coastal Cooperative drilled 28 rotosonic cores (max. depth=80m) through Quaternary deposits in an area that includes the Suffolk paleoshoreline (MIS5e), the paleo-Roanoke, Tar-Pamlico, and Neuse River valley systems, and the Outer Banks barrier island chain. Landscape features on the mainland include marine, estuarine and fluvial terraces at elevations below 12m.

Regional-scale cross sections were prepared by an integration team that worked through consensus to establish correlations using multiple lines of evidence – process sedimentology, facies analysis, foraminiferal biofacies, amino acid racemization and carbon-14 ages, geomorphology, and offshore geophysics. The profiles are oriented parallel to: 1) the strike of the barrier island chain; 2) regional strike on the mainland; and 3) a dip section that transects the Suffolk Scarp. Facies identified in core include fluvial, estuarine, barrier island, shoreface, and shelf deposits. Regional reflectors (Q0, Q30, Q50, Q99), mapped along adjacent offshore and backbarrier seismic lines, were projected into cross sections and correlated with unconformities in cores, to define major boundaries and establish the stratigraphic framework.

Q0, Q30, and Q50 are respectively interpreted as the bases of early (1.8 or 2.6ka), middle (780ka) and late (130ka) Pleistocene deposits, and also correspond (respectively) to the lower boundaries of aminozones 4, 3 and 2. Regional correlation models (Mixon and others, 1989) suggest that these reflectors rise and merge landward with early, middle and late Pleistocene shoreline maxima that are associated (respectively) with the Surry Scarp (31m), an unnamed scarp at 14m, and the Suffolk Scarp (10m). Q99 marks the incision at the last glacial maximum, and is overlain by late Pleistocene to Holocene lowstand (LST) and transgressive (TST) deposits.