SUMMARY AND CONCLUSIONS

The Cape May Zoo corehole recovered Miocene–?Pliocene Kirkwood and Cohansey sequences and Pleistocene Cape May sequences allowing for:

Drilling at Cape May Zoo confirmed the regional significance of the following:

A major objective of the Cape May Zoo corehole was to improve the resolution of Miocene sequences between Ocean View and Cape May and the hydrogeologic framework on the Cape May Peninsula (Fig. F19). Aquifer terminology follows the usage of Lacombe and Carleton (2002). The Holly Beach water-bearing zone, an unconfined aquifer, correlates with the Cape May Formation Unit II (and possibly Unit I) (Fig. F19). Sandy sections assigned to this unit are ~60 ft (18.3 m) thick at this site (0–60 ft; 0–18.3 m), although the resistivity log suggests it might be only 35 ft (10.67 m) thick (0–35 ft; 0–18.3 m). A 34- to 57-ft-thick (10.36–17.37 m) confining bed contained within Cape May Formation Unit 1 separates the Holly Beach zone above from the Estuarine Sand aquifer below. The Estuarine Sand aquifer (Fig. F19) is ~90 ft (27.43 m) thick (93.6–180.4 ft; 28.53–54.99 m) and correlates with Sequence Ch4 and the upper part of the newly named Stone Harbor Formation. Gill (1962) incorrectly correlated this aquifer with the estuarine sand facies of the Cape May Formation; consequently, a new aquifer name might be given to this dominantly sandy interval that does not correlate with the Cape May Formation. A ~20-ft-thick (6.1 m) confining bed (180.4–200 ft; 55–61 m) in the upper part of Sequence Ch3 (and lower part of the newly named Stone Harbor Formation) separates the confined Estuarine Sand aquifer above from the confined Cohansey aquifer below (Fig. F19). The Cohansey aquifer is 60 ft (18.3 m) thick at this site. The Cohansey aquifer is separated from the Rio Grande aquifer (405–480 ft; 123.4–146.3 m) by a thick (150 ft; 45.7 m) confining bed (upper part of Wildwood-Belleplain confining unit of Sugarman, 2001) correlative with the Kirkwood-Cohansey and Kw3 sequences (Fig. F19). Within this confining bed (250–405 ft; 76.2–137.6 m) is potentially a thin unnamed aquifer from 325 to 345 ft (99 to 105 m). The Rio Grande aquifer is separated from the upper part of the Atlantic City 800-foot sand by a thick (150 ft; 45.72 m) confining unit (lower part of Wildwood-Belleplain confining unit from 480 to 630 ft (146.3 to 192 m). A thin (20 ft; 6 m) unnamed aquifer is also present within this confining unit from 530 to 550 ft (161.5 to 167.6 m). The corehole terminated in the Atlantic City 800-foot sand aquifer. At this site, the upper sand is composed of sand from Sequences Kw1b and Kw1c. The relatively thin clay from 650 to 661 ft (198.1 to 201.5 m) probably has limited capabilities as a confining bed separating the two sands within the Shiloh Marl Member of the Kirkwood Formation (Fig. F19).

The Cape May Zoo corehole focused on early–middle Miocene sequences, recovering nine dateable sequences of this age (Sequences Kw-Ch2, Kw-Ch1, Kw3, Kw2b, Kw2a3, Kw2a2, Kw2a1, Kw1c, and Kw1b) and two poorly dated upper Miocene sequences (?Ch3 and ?Ch4). Though operations during Legs 150X and 174AX drilled 11 onshore coreholes, Miocene sections progressively thin dramatically and are temporally much less complete updip. Along a projected dip profile, the most downdipping sites are Bethany Beach, Cape May, and Cape May Zoo, with ~12, ~13, and 11 Miocene sequences, respectively. Despite the success of sampling numerous sequences at the Cape May Zoo corehole, including the first verification of Sequence Kw1c, which is really quite limited, hiatuses limit our understanding of Miocene sequences onshore. For example, numerous penetrations of the Miocene section during Legs 150X and 174AX have provided a sampling of a maximum of 50% of the early to middle Miocene (~11.2–23.8 Ma). At Cape May Zoo, our age estimates suggest that as little as 2.5 m.y. of this 12.6-m.y. interval is represented (Fig. F15). There is simply more gap than record onshore. We did manage to capture one or two possible LSTs at Cape May Zoo, but LSTs are generally lacking and the sections onshore only represent a small portion of the record.

The Cape May Zoo corehole complements offshore drilling during IODP Expedition 313 (summer 2007) that will also target thick lower–middle Miocene sequences. Seismic evidence shows that the offshore sections beneath the inner continental shelf are more complete and reflect a full range of systems tracts. Though several discontinuous holes have sampled Miocene sequences beneath the inner shelf (AMCOR, ACOW), there has been no continuous sampling of these sequences where they are their thickest, the imprint of sea level change is most clearly recorded, and the ties between facies distribution and sequence architecture can be firmly established. Expedition 313 will sample these critical facies and bring the New Jersey Sea Level/Mid-Atlantic Transect to its conclusion.