This chapter is the site report for Sea Girt corehole, the tenth continuously cored and logged onshore site drilled as part of the CPDP. The CPDP began with drilling at Island Beach (March–April 1993), Atlantic City (June–August 1993), and Cape May (March–April 1994) as part of Ocean Drilling Program (ODP) Leg 150X (Miller et al., 1994a,1994b, 1996a; Miller, Newell, and Snyder, 1997). These three sites targeted Oligocene–Miocene sequences and tried to unravel icehouse sea level changes tied to continental slope drilling by the JOIDES Resolution on Leg 150 (Miller and Mountain, 1994; Miller et al., 1996b, 1998).
Leg 174AX continued onshore drilling at the following locations:
These sites provided 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 Committee designated drilling at these sites as ODP Leg 174AX. In total, these previous coreholes recovered 6082 ft (1854 m) from 6991.5 ft (2131.01 m) drilled (recovery = 87%).
Despite logistic and scientific success in onshore coring to date, there is a significant gap in our understanding of Upper Cretaceous greenhouse sequences. Both Ancora and Bass River are excellent Upper Cretaceous sections, as summarized in Miller et al. (2004), but they each have important limitations. Drilling updip at Ancora recovered unaltered Upper Cretaceous strata (531 ft; 161.85 m) that were dated using integrated Sr isotopic stratigraphy and biostratigraphy, with resolution as good as ±0.5 m.y. (Miller et al., 2004). However, because of its updip location, the section at Ancora was thin and poorly fossiliferous in a few critical sections (e.g., the Cenomanian/Turonian boundary, middle Campanian Englishtown sequence). Drilling at Bass River provided thicker Upper Cretaceous sequences (700 ft; 213.36 m). Although the ages of sequences agree well between Bass River and Ancora (Miller et al., 2004), Sr isotopic values at Bass River below 1500 ft (450 m) were affected by diagenesis, resulting in greater age uncertainty than at Ancora. One or more additional sections are needed to verify the regional significance and global ages of these greenhouse sequences and attendant sea level changes. The "Goldilocks" location (neither too far updip nor too far downdip) is midway between Bass River and Ancora.
We have targeted two sites between Ancora and Bass River that should provide ideal settings for sampling Upper Cretaceous sequences. The first, along strike to the south at Millville, New Jersey, was chosen primarily to sample important aquifers and the NJGS paid for all drilling costs for this hydrostratigraphic test corehole in summer 2002 (Sugarman, et al., this volume). Because Upper Cretaceous sections thin along strike toward Millville, only 439.6 ft (133.99 m) of Cretaceous strata were recovered. Nevertheless, this site is very useful in evaluating Upper Cretaceous facies variations and provides a key location for mapping Cretaceous hydrogeologic units (Sugarman et al., this volume, 2006) and sequences (Kulpecz, 2005). Regional trends show that the Upper Cretaceous thickens toward the north of the Ancora-Bass River dip transect (Perry et al., 1975; Olsson et al., 1988) (Fig. F1). Stratigraphic sections from poorly sampled wells at Toms River, Sandy Hook, and Fire Island show that a location between Toms River and Sandy Hook will provide the thickest Upper Cretaceous marine section. Though the Upper Cretaceous thickens further toward Fire Island, there are no Cenomanian–Turonian strata there and the section is very sandy (hence poorly fossiliferous and nonmarine in parts). Thus, the NSF funded drilling of a 1600 ft (187.68 m) corehole at Sea Girt, New Jersey, along strike of Millville. This site will be tied into the nearshore seismic grid collected in May 2003 by G.S. Mountain, N. Christie-Blick, S. Pekar, and C. McHugh in May 2002 that includes Chirp sonar (1 m resolution) and high-resolution (5 m vertical) multichannel seismic data (Fig. F1), allowing us to evaluate Upper Cretaceous sequences with a resolution not previously possible.