Cenozoic evolution of the New Jersey Coastal Plain: changes in sea level, tectonics, and sediment supply

Abstract

The New Jersey Coastal Plain Drilling Project continuously cored three boreholes at Island Beach, Atlantic City, and Cape May, New Jersey. Sequence boundaries in the cores are expressed as physical surfaces, lithofacies breaks, and paraconformities (hiatuses) recognized using biostratigraphy and Sr-isotopic stratigraphy. By drilling along dip and strike profiles, we assembled a mosaic of 29 Paleocene to Miocene sequences and dated them using integrated magnetostratigraphy, biostratigraphy, and isotopic stratigraphy. Correlation between major late middle Eocene to middle Miocene (42-10 Ma) onshore sequence boundaries and δ 18 O increases (inferred glacioeustatic lowerings) indicates that eustasy exerts a primary control on sequence boundaries. Onshore sequence boundaries also correlate with Miocene unconformities on the New Jersey shelf and slope, Oligocene to middle Miocene unconformities in Florida, early Oligocene unconformities in Alabama, and the sequence boundaries of Exxon. Such regional and interregional correlations support a eustatic control. However, early middle Eocene correlations between sequence boundaries and δ 18 O increases are equivocal, and it is not clear that glacioeustatic changes occurred at this time. In contrast, early Eocene sequence boundaries do not correlate with δ 18 O change, and we infer ice-free conditions at this time; nevertheless early Eocene sequence boundaries do correlate with those of Exxon, indicating that they may record global sea-level events. However, there is no known mechanism for explaining such large, rapid early Eocene eustatic variations other than glacioeustasy. Paleocene sequence boundaries apparently do not match the Exxon sequence boundaries, and further study of New Jersey Paleocene sequences is warranted. (...)