Abstract

High-resolution seismic profiles over a 25,000 km 2 area off New Jersey illustrate the effects of high-amplitude, high-frequency eustasy on a slowly subsiding (<0.2 mm/yr) passive margin. Analysis of 1600 km of Geopulse TM , Uniboom TM Minisparker TM and air-gun profiles reveals four depositional sequences with a maximum total thickness of 100 m at the shelf edge. Correlation of these sequences to biostratigraphic and aminostratigraphic data from drill sites suggests all of these sequences may be postoxygen isotope stage 6 ( approximately 140 ka). Sequences I and IV appear to correspond to the major glacial-interglacial sea level changes ( approximately 120 m) during oxygen isotope stages 6/5 and 2/1, respectively. Sequences II and III reflect smaller scale sea level fluctuations. All sequence boundaries are interpreted as type 1, and sequences are predominantly composed of transgressive systems tracts (TST) and lowstand systems tracts (LST). Much of the TST was deposited as incised-valley fills; parasequences in the TST commonly are isolated and fragmented. The low subsidence rate and high-frequency (20 k.y.) eustatic oscillations result in extensive erosion and reworking of previously deposited sediments, both by fluvial incision during lowstands and marine erosion during transgressions and highstands. On continental margins where subsidence rates and sediment supply are low relative to rates of eustasy, sequences are thin, fragmented, and difficult to correlate. Local effects, such as shifting river drainage, salt diapir movements, and glacial isostasy, can significantly influence sequence preservation on such margins.

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