Abstract:
We recognized and dated Oligocene to middle Miocene sequence boundaries on the NJ Coastal Plain and slope by integrating Sr-isotopic, magneto-, and biostratigraphy (planktonic foraminifera, nannofossils, dinocysts, and diatoms). Unconformities in the coastal plain boreholes (Island Beach, Atlantic City, Cape May, Bass River) were identified on the basis of physical evidence (including irregular contacts, reworking, bioturbation, and major facies changes) and well-log characteristics. Offshore, sequences were recognized beneath the shelf based on seismic criteria (erosional truncation, toplap, onlap and/or downlap geometries) and traced to the slope where they were dated. NJ studies show that for at least the past 42 m.y., sequence boundaries correlate (within + or -0.5 m.y.) onshore and offshore. In addition, the sequences correlate with Oligocene sequences in Florida and Alabama and with Miocene sequences in Florida and the Bahamas. These comparisons indicate that Oligocene-Miocene sequences fulfill our first expectation of a global process such as eustasy: they correlate within the requisite resolution (+ or -0.5 m.y.) both regionally (e.g., onshore-offshore of New Jersey) and interregionally (New Jersey-Florida-Alabama-Bahamas). In addition, both onshore and offshore NJ sequences correlate with glacioeustatic lowerings inferred from deep-sea oxygen isotopic records obtained far from continental margins. These correlations appear to link margin erosion with glacioeustatic change on the m.y. scale. However, there are age uncertainties in the correlations among onshore, offshore, and deep-sea sites that render it difficult to demonstrate unequivocally a causal relationship between sequence geometries and glacioeustatic change. Preliminary oxygen isotopic results from NJ slope Site 904 and Bahamas Site 1006 provide direct evidence that is independent of age uncertainties for a causal connection between latest Oligocene to Miocene oxygen isotopic increases and sequence boundaries.