Abstract

We use magnetostratigraphy and Sr-isotope stratigraphy to improve stratigraphic control for the Eocene to Oligocene of the New Jersey coastal plain (ACGS4 borehole). Magnetostratigraphy in many cases is complicated in outcrop sections of shallow-water (<200 m paleodepth) sediments by low remanence and weathering; we minimize these problems by analyzing large samples obtained from the ACGS4 borehole and construct a firm magnetochronology for the early to middle Eocene. Sr-isotope stratigraphy confirms biostratigraphic evidence for a previously unknown uppermost Eocene to lowermost Oligocene unit and delineates a "middle" Oligocene hiatus that is unresolvabie using biostratigraphy alone. We recognize hiatuses and associated unconformities on the New Jersey margin near the lower Eocene/middle Eocene boundary, within the middle Eocene, and in the "middle" Oligocene and correlate these events with similar hiatuses observed in other continental-shelf, slope, and epicontinental settings. In addition, a hiatus probably occurred near the middle Eocene/upper Eocene boundary. We conclude that the interregional distribution of these Eocene-Oligocene hiatuses indicates a global cause: eustatic change.

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