EOCENE-OLIGOCENE BENTHIC FORAMINIFERAL BIOFACIES AND DEPOSITIONAL SEQUENCES AT THE ACGS NUMBER-4 BOREHOLE, NEW-JERSEY COASTAL-PLAIN

Previous studies of the Eocene-lowermost Oligocene section at the ACGS #4 borehole (Mays Landing, NJ; Fig. I) recognized physical surfaces u sing litho- and gamma log- stratigraphy and inferred hiatuses using bi o-, magneto-, and isotopic stratigraphy. This study integrates Eocene to Oligocene benthic foraminiferal studies with previous work, identif ies additional paraconformities, and places benthic foraminiferal chan ges into a sequence stratigraphic framework. Quantitative and qualitat ive analyses of benthic foraminifera indicate neritic (0-200 m) paleod epths throughout the Eocene section, despite high relative abundances of planktonic foraminifera. Benthic foraminiferal assemblages at the A CGS #4 borehole indicate outer neritic (100-200 m) paleodepths in the Deal Member (lower-middle Eocene), except for an intrusion of a shallo wer (middle neritic: 30-100 m) fauna near the lower/middle Eocene boun dary. Paleodepths shallowed up-section. to middle neritic in the Shark River Formation (upper middle-lower upper Eocene) and ACGS alpha Unit (upper Eocene-lowermost Oligocene) and inner neritic (0-30 m) to marg inal marine in the Mays Landing Unit (lowermost Oligocene). Although t he ACGS #4 borehole provides a reasonably continuous Eocene to lowermo st Oligocene shallow-water record, integrated stratigraphic studies (s equence, litho-, bio-, isotopic and magneto-stratigraphy) including be nthic foraminifera document that deposition was punctuated by at least 6 hiatuses. The hiatuses are associated with unconformities that brac ket 7 sequences: Deal Member Sequences A, B, and C; Shark River Format ion. Sequences Di and Dii; ACGS alpha Unit Sequence E; and the Mays La nding Unit Sequence F. Major biofacies and paleobathymetric changes ar e associated with most of the unconformities that define the bases of the sequences. The unconformities at the ACGS #4 borehole correlate or are consistent with major sequence boundaries of Haq et al. (1987).