Aminostratigraphic results from Cape Lookout, N.C., and their relation to the preserved Quaternary marine record of SE North Carolina

Abstract

Aminostratigraphic data were obtained for Mulinia lateralis samples from closely spaced drillholes on the Cape Lookout, North Carolina barrier islands. Two major aminozones are recognized in the subsurface section based upon D-alloisoleucine/L-isoleucine (A/I) values. These major aminozones can each be subdivided into two additional aminozones based upon direct comparisons with Mulinia A/I data from other North Carolina localities. Correlation of the Cape Lookout Mulinia aminostratigraphy with U-series calibrated A/I data in N.C. indicates that the sampled units represent deposition during the middle to late Pleistocene. The four Cape Lookout aminozones may be assigned to late and early stage 5 (or possibly stages 5 and 7), a portion of the interval during stages 17–19, and at least one interglacial in stages 25–31 of the oxygen isotope record based on correlation to calibrated sites and kinetic model extrapolation. The aminostratigraphic data obtained from the Cape Lookout barrier islands and nearby areas indicate that there are significant differences in the extent of preservation of the Pleistocene sedimentary record to the southwest of Cape Lookout compared with that to the north-northeast. All four of the recognized Cape Lookout aminozones are present in the subsurface section to the north-northeast of Cape Lookout. In contrast, the two late Pleistocene aminozones are almost completely absent in the subsurface of the barrier islands, and in Onslow Bay, to the southwest of Cape Lookout. These aminostratigraphic interpretations are consistent with the incomplete stratigraphic record recognized by previous investigators for the Cape Lookout-Onslow Bay area. The calibrated kinetic model age estimates for the Cape Lookout aminostratigraphic data now permit quantification of these stratigraphic gaps. The detailed aminostratigraphic results from Cape Lookout also have significant consequences for regional aminostratigraphic correlations on the Atlantic Coastal Plain, and provide valuable information with which to test contrasting models proposed for regional correlation within the context of the preserved stratigraphic record.