T226 Mid-Atlantic Coastal Plain Stratigraphy and Paleontology

Wednesday, 7 November 2012
8:00 AM - 12:00 PM
203A

THE LAST GLACIAL AND DEGLACIATION: INSIGHTS FROM CONTINUOUS CORING ON THE NEW JERSEY CONTINENTAL SHELF

Paper number: T226-15
Program: Technical Sessions
Time: 11:40 AM – 11:55 AM

Authors

Abstract

Sedimentation on the New Jersey margin is highly variable, particularly during the last glacial cycle. Sea level changes impact depositional processes, leading to areas of erosion, accumulation, incision and reworking, and acoustic artifacts such as chaotic reflectors and sedimentary wedges. The record of change can provide insight into the nature of glacially driven sea level change and the stratigraphic response; however, the variability we seek to study is often an impediment to significant core recovery in this challenging sampling environment. Coring using the DOSECC AHC-800 drilling system provided continuous recovery at 3 sites on the outer shelf, and using an extensive set of high-resolution CHIRP profiles, targeted fluvial incisions, channel fill and interpreted exposure surfaces associated with glacial lowstands. Textural and benthic foraminiferal data were evaluated to determine the environments of deposition and estimate paleo-depths. Carbon dating of wood and shell material provided the temporal framework for interpretation. K-Ar dating of hornblende crystals provided insight into the source region of sediments.

The oldest sediments recovered are present above and below R, a time-transgressive regional unconformity. Estimates for formation of R on the mid-shelf are ~45 Ka, around the MIS3b - MIS3b/a transition at shallow water depths. Sediments deposited at this time were delivered from a paleo-Hudson system to a mid-shelf position, and had a bimodal source (NJ hinterland and the Hudson River drainage basin). As sea level fell within MIS2, sediments were reworked on the shelf, and channels were incised (~30 – 16 Ka). Infilling of the fluvial system occurred rapidly during latest MIS2 (16-14Ka), shortly after the shoreline began to migrate landward. The CHIRP data indicate a reinvigoration of flow around 14 Ka at the time of Meltwater Pulse 1A, although we find no evidence for jökelhlaup deposition associated with the Intra-Allerød cold period ~13 Ka. Fairly homogenous Recent reworked sediments cap the sequence, and have hornblende ages that are consistent with a NJ highlands source region, indicating a greater input by NJ rivers. Our integrated analysis complements previous studies and elucidates significant regional differences in deposition, particularly north of the Hudson Canyon system.