16. LOWER TO MIDDLE EOCENE BENTHIC FORAMINIFERAL BIOFACIES AND LITHOSTRATIGRAPHIC UNITS AND THEIR RELATIONSHIP TO SEQUENCES, NEW JERSEY COASTAL PLAINJames V. Browning,2 Kenneth G. Miller,2,3 and Richard K. Olsson2 |
ABSTRACTWe use benthic foraminifers to evaluate water-depth changes within and between eight lower to middle Eocene sequences and examine the relationship between these sequences and previously recognized lithostratigraphic units. Integrated sequence and magnetobiostratigraphic studies presented elsewhere in this volume are used to recognize and correlate these sequences in the New Jersey Coastal Plain (Island Beach, Atlantic City, Allaire, and ACGS#4 boreholes). Based on drilling at Allaire State Park, adjacent to the outcropping stratotypes, we correlate the Farmingdale and Deal Members of the Manasquan Formation to Sequences E1–lower E2 (lower lower Eocene) and upper E2–E4 (upper lower Eocene), respectively. We tentatively correlate the Squankum Member of the Shark River Formation to Sequence E5 (lowermost middle Eocene). The lower Shark River Formation correlates to Sequences E6 and E7 (lower middle Eocene), the upper Shark River Formation to Sequence E8 (upper middle Eocene), and the Toms River Member of the Shark River Formation to Sequence E9 (?upper Eocene). Nine benthic foraminiferal biofacies are distinguished, and paleodepths for each are estimated using a paleoslope modeling technique. Water depths of ~130 m existed in the boreholes examined throughout most of the early to middle Eocene, with maximum water depths of 185 ± 15 m in the early Eocene. Shallower water depths (50 ± 10 m at Allaire to 75 ± 15 m at Atlantic City) occurred in the middle Eocene. The timing and magnitude of water-depth changes in New Jersey Eocene sequences are similar to the eustatic changes inferred by Exxon. The coastal plain was not subaerially exposed during this time interval, and it is unknown what mechanism formed the unconformities found on the shelf at this time. |
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