18. UPPER EOCENE SEQUENCE STRATIGRAPHY AND THE ABSECON INLET FORMATION, NEW JERSEY COASTAL PLAIN1

James V. Browning,2 Kenneth G. Miller,2,3 and Laurel M. Bybell4

ABSTRACT

We evaluate the age, benthic biofacies, and sequence stratigraphy of thick and well-recovered upper Eocene sediments from the New Jersey Coastal Plain. These strata are herein defined as a lithostratigraphic unit and named the Absecon Inlet Formation. The formation is divided into upper and lower portions. At its type locality in the Atlantic City borehole, the lower portion of the Absecon Inlet Formation consists of 171 ft (52 m) of glauconitic silts and silty clays and is assigned to calcareous nannoplankton Zone NP 19/20 (late Eocene). At the ACGS#4 borehole, the type locality for its upper portion, the formation consists of slightly sandy clays and is assigned to Zone NP 21 (late Eocene to earliest Oligocene). The continuous stratigraphic occurrence of Hantkenina spp. in these sediments is evidence of an Eocene age for the upper portion of the Absecon Inlet Formation. Benthic foraminiferal analysis reveals five biofacies in the Absecon Inlet Formation, three of which can be related to paleowater depth: a Siphonina biofacies inhabited water depths of 75 25 m; a Cibicidoides biofacies inhabited water depths of 100 30 m; and a Globobulimina biofacies inhabited water depths of 125 30 m. In addition, a Gyroidinoides biofacies occurs only within transgressive systems tracts. A Bulimina jacksonensis biofacies is believed to be related to a circum-Atlantic paleoceano-graphic event unrelated to depth changes on the shelf. Gamma-log, lithologic, and faunal/floral data are used to interpret the sequence stratigraphic architecture of the Absecon Inlet Formation. We conclude that the timing of unconformities (sequence boundaries) and maximum flooding surfaces within the Absecon Inlet Formation is consistent with the eustatic record of Exxon and the global delta18O record.

1Miller, K.G., and Snyder, S.W. (Eds.), 1997. Proc. ODP, Sci. Results, 150X: College Station, TX (Ocean Drilling Program).
2Department of Geological Sciences, Rutgers University, Piscataway, NJ 08855, U.S.A.
3Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, U.S.A.
4Correspondence author: 926 National Center, U.S. Geological Survey, Reston, VA 22092, U.S.A. lbybell@geochange.er.usgs.gov