This chapter is the site report for Cape May Zoo corehole (Fig. F1), the eleventh continuously cored and logged onshore site drilled as part of the NJCPDP. The NJCPDP began with drilling at Island Beach (March–April 1993), Atlantic City (June–August 1993), and Cape May (March–April 1994) as part of Leg 150X (Miller et al., 1994a, 1994b, 1996a; Miller and Snyder, 1997). Drilling at these three sites targeted Oligocene–Miocene sequences in an attempt to unravel Icehouse sea level changes tied to continental slope drilling by the JOIDES Resolution during ODP Leg 150 (Miller and Mountain, 1994; Miller et al., 1996b, 1998a).
Operations during Leg 174AX continued onshore drilling at the following locations:
• Bass River, New Jersey (October–November 1996) (Miller et al., 1998b), targeting Upper Cretaceous to Paleocene strata poorly sampled during Leg 150X.These sites provide a chronology of sequences over the past 100 m.y. (e.g., Miller et al., 2005). The Joint Oceanographic Institutions for Deep Earth Sampling Planning Committee and Science Planning Committee designated drilling at these sites as ODP Leg 174AX. In total, these previous coreholes recovered 11,685 ft (3,561 m) from 14,266.5 ft (4,348 m) drilled (recovery = 82%).
The Cape May Zoo corehole, the final Leg 174AX corehole, was selected between the Ocean View (Leg 174AX) and Cape May (Leg 150X) sites to provide insights into lower Miocene to Holocene sequences and hydrostratigraphy and to complement offshore drilling during Expedition 313. One surprise in drilling to date was the relative completeness of the lower to middle Miocene section of the Leg 150X Cape May site compared to other onshore coreholes, with at least nine sequences represented. Even the more basinal Bethany Beach site (Leg 174AX) was less complete in the early Miocene than Cape May (see Browning et al., 2006, for detailed comparison). Several of these sequences pinch out upbasin toward the Ocean View site (Leg 174AX), and it was hoped that drilling at Cape May Zoo would capture these sequences.
The Kirkwood Formation consists of sand and silty clay usually influenced by a delta. The formation has been dated as lower to middle Miocene and divided into nine sequences at the Cape May borehole (Miller et al., 1996a). Two of these sequences, Kw1c and Kw2c, have only been recognized at Cape May, and one major unfulfilled objective of drilling at the Ocean View site (Miller et al., this volume) was to validate these two sequences. Drilling at Ocean View did sample higher order sequences within the Kw1 and Kw2 sequences, but Sr isotopic studies make it clear that Sequence Kw1c pinches out in the 17 mi from Cape May to Ocean View. It also appears that Sequence Kw2c is not present at Ocean View, though this needs to be reexamined.
Drilling at Cape May Zoo targeted Kirkwood sequences, particularly Sequence Kw1c, which was estimated to lie at ~650–700 ft at this site. Because the Kw1c sequence contains a potentially useful aquifer, the NJGS funded drilling of the Cape May Zoo corehole.
An unnamed estuarine gray sand and clay unit was sampled at the Cape May corehole and dated with dinocysts as upper Miocene (de Verteuil, 1997). Coeval yellow Cohansey Formation was sampled in the Ocean View corehole and dated with dinocysts as upper Miocene Zone DN8 (Miller et al., this volume). Drilling at Cape May Zoo recovered a thick gray estuarine gray sand and clay unit that appears to correlate with the Cape May corehole.
The Kirkwood sequences at the Cape May Zoo site are well characterized lithologically and with downhole logs and contain enough shells throughout that we were able to construct a detailed Sr isotope chronology for the Miocene. Numerous Kirkwood sequences can be recognized by comparison of the preliminary descriptions with the downhole gamma ray and resistivity logs. We conducted a preliminary correlation of the Cape May Zoo Kirkwood sequences with Cape May and Ocean View boreholes and believe we have at least nine Kirkwood sequences: Kw-Ch2, Kw-Ch1, Kw3, Kw2c, Kw2b, Kw2a3, Kw2a2, Kw2a1, and Kw1c. Preliminary correlations suggest that each of these sequences is represented at two of the three coreholes, extending the validated number of lower–middle Miocene sequences to 11 (i.e., including the Kw1b, Kw1c, and Kw0 sequences). Preliminary correlations suggest that the Kw-Ch, Kw3, and Kw1c sequences may be divided into higher order sequences, further suggesting the presence of from 14 to 16 lower to middle Miocene sequences.
The following lithologic and sequence stratigraphy of the Kirkwood Formation is a preliminary interpretation based on core-log correlations between the Ocean View, Cape May Zoo, and Cape May coreholes.
The Cape May Zoo site is critical for understanding the hydrogeology of the rapidly developing Cape May Peninsula. The Atlantic City "800-foot" sand aquifer is a critical aquifer in the New Jersey coastal plain, yet its distribution is complicated in the Cape May Peninsula. At the Cape May site, three sand bodies can be mapped within the Atlantic City 800-foot sand vs. two outside of the peninsula (e.g., Atlantic City). The highest of these aquifer sands is associated with the HST of Sequence Kw1c, whereas the medial and lower aquifers are associated with the HST of Sequences Kw1b and Kw1a as they are at Atlantic City and Ocean View (Sugarman et al., 2006). The Kw1c sequence and associated aquifer sand clearly pinches out 15 km (9 mi) to the north at Ocean View (Sugarman et al., 2005). Drilling at Cape May Zoo targeted these aquifers in an effort to resolve their relative continuity and interconnectedness. Because this corehole is critical to the citizens of this region, the NJGS paid for all drilling costs for the Cape May Zoo corehole. The National Science Foundation (Earth Science Division, Continental Dynamics Program) provided support for field and subsequent analyses and ODP provided all publication support.