Upper Eocene sequence stratigraphy and the Absecon Inlet Formation, New Jersey Coastal Plain

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 paleoceanographic 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 δ 18 O record.

Bass River Site

“…There is an erosional surface at 840.1 ft (256.06 m; 840.5 ft on figure) separating glauconite clay above from brown clay below. The sequence between 840.1 and 684.9 ft (256.06 and 208.76 m) is probably Sequence E10 of Browning et al (1997a); the possible subdivision of E10 into two sequences by a surface at 770.7 ft (234.91 m) is consistent with results at Leg 150X boreholes (Browning et al, 1997a).…”

“…8). The thin sequence from 684.6 to 675.5 ft (208.67−205.89 m) may be equivalent to Sequence E11 of Browning et al (1997a).…”

“…8). A distinct erosional surface at 770.7 ft (234.91 m) may be a sequence boundary that splits Sequence E10 of Browning et al (1997a) into two possible sequences.…”

“…lower Shark River Fm. Browning et al (1997a) and Browning et al (1997c). See Figure 4 for key to symbols.…”

Two-Dimensional Paleoslope Modeling: A New Method for Estimating Water Depths of Benthic Foraminiferal Biofacies and Paleoshelf Margins

“…(See Acknowledgments section for location of archived data and factor analysis.) These biofacies were Browning et al 1997), Oligocene (ML, O1-O6; Pekar et al 1997), and earliest Miocene (Kw0 and Kw1a; Miller et al 1997) sequences and well locations projected along strike onto the dip profile from line A to AЈ (see Figure 1). The sections are hung from the base of sequence Kw1aЈ, which represents the datum line.…”