SUMMARY AND FUTURE WORK

The Sea Girt corehole recovered expanded sections of the upper Englishtown, Merchantville, Magothy, and Bass River sequences, allowing for

1. Better resolution and dating of Upper Cretaceous sequences, which provides a test of the age and regional significance of sequences cored at Bass River and Ancora;
2. Evaluation of facies models;
3. Ties to nearby outcrop sections, particularly the Magothy Formation and its members; and
4. Evaluation of hydrostratigraphic units.

Drilling at Sea Girt confirmed the regional significance of the following:

1. The Navesink II (late Maastrichtian to earliest Danian) and Navesink I (early Maastrichtian) sequences;
2. The upper Englishtown Formation and sequence. Though the sequence remains only moderately well dated (worse than 1 m.y. uncertainty) (Fig. F18), drilling confirms that it is a distinct lithostratigraphic and sequence stratigraphic unit deserving its own name;
3. Two uppermost Santonian sequences within the Merchantville Formation;
4. Two new sequences in the Magothy Formation (Sequences IVA and IVB; Kulpecz, 2005) that were hinted at in outcrop studies but only confirmed by continuous coring;
5. The Magothy I, II, and III as distinct and differentiable sequences (Sea Girt is the first corehole to sample all three); and
6. Division of the Bass River Formation into at least three sequences and possibly five (though the BR0 and BR0.5 sequences might best be called the Potomac IIIb and IIIc sequences). Our previous synthesis of Bass River and Ancora identified 11 to 14 Upper Cretaceous sequences. With Sea Girt, we affirm 14 of these sequences and suggest that there are, in fact, at least 18 sequences.

Though facies models for Upper Cretaceous coastal plain sequences have been well described (Owens and Gohn, 1985; Sugarman et al., 1995; Miller et al., 2004), drilling at Sea Girt, because of its critical position in Monmouth County, allows ties of numerous gamma ray logs from various uncored wells into the thickest Upper Cretaceous section cored thus far. This "Rosetta Stone" has allowed the mapping of Upper Cretaceous sequences and the identification of their sediment sources. The Sea Girt corehole has clearly identified the complex facies of the Magothy Formation and allows detailed evaluation of the represented environments (Sugarman et al., 2005). This allows fairly precise pattern matching of the Magothy sequences identified at Sea Girt with members of the Magothy Formation that crop out in nearby portions of Middlesex County, specifically the Magothy IVB (probable equivalent of the Cliffwood Beds), IVA (probable equivalent of the Morgan Beds), III (probable equivalent of the Amboy Stoneware Clay), MII (probable equivalent of the Old Bridge Sand and South Amboy Fire Clay), and MI (probable equivalent of the Sayreville Sand) sequences. Though such pattern matching is risky, the fit between the corehole and the outcrop lithologies is compelling.

Numerous potential aquifers were penetrated at Sea Girt. Though relatively thin in this updip location, the Kirkwood Formation contains two medium–coarse confined sand beds at ~100 and 110 ft (30.48 and 33.53 m) that may be the updip equivalent of the Atlantic City 800-ft sand aquifer of Zapecza (1989). The upper Shark River Formation fine sands (~136–170 ft; 41.45–51.82 m) appear to be an aquifer in hydrodynamic continuity with these coarser sands. The Mount Laurel Formation (566–670 ft; 172.52–204.22 m) appears to be a good aquifer, but it is the upper Englishtown sands (691–755 ft; 210.62–230.12 m) that comprise the richest of the aquifers. The combined effects of these two aquifers on the corehole almost resulted in the loss of the hole. Several of the sands in the Magothy Formation have potential for groundwater, but the Old Bridge Sand (1212.7–1225 ft; 369.63–373.38 m) appears to be coarsest and have greatest potential. Potential aquifers within the Bass River and Potomac Formations are generally finer grained and thinner, though the possible equivalent to the Farrington Sand (1565–1580 ft; 477.01–481.58 m) is moderately coarse grained and sufficiently thick to be screened.

The Sea Girt corehole provided material needed to address the primary purposes of the coastal plain drilling project: evaluate and date sequences, obtain a paleowater depth record, and thus provide data needed to extract a global sea level record through backstripping. Work is ongoing to provide the age, paleodepth, and porosity data needed to backstrip this site and compare it with published backstripped records from Ancora, Bass River (Van Sickel et al., 2004), and ongoing backstripping studies of Millville. Miller et al. (2005) provided a synthesis that includes a global sea level estimate of the past 100 m.y. that was derived from backstripping onshore coreholes. The Cretaceous portion of this synthesis was based only on records from Bass River and Ancora; we now have the material from Millville and Sea Girt to test the Upper Cretaceous portion of the synthesis.

The Sea Girt borehole will also provide an opportunity to tie Upper Cretaceous sequence into nearshore seismic profiles. Previous seismic correlations of onshore boreholes have been largely limited to Miocene correlations from Island Beach, Atlantic City, and Cape May to the Cape Hatteras 0698 multichannel seismic (MCS) data set (Monteverde et al., 2000). While this has provided insight into the seismic expression of prograding Miocene sequences, it has not provided information on Upper Cretaceous–Paleogene sequences. The thick Upper Cretaceous section at Sea Girt, with its excellent sequence stratigraphic expression, can be tied to a grid collected in May 2003 by G.S. Mountain, N. Christie-Blick, and S. Pekar and C. McHugh in May 2002 that includes Chirp sonar (1-m resolution) and high-resolution (5 m vertical) MCS data (Fig. F1), allowing us to evaluate Upper Cretaceous sequences with a resolution not previously possible.

The Sea Girt corehole will provide material for understanding some of the more profound events in Earth history. Though the K/Pg boundary was discontinuous at Sea Girt, the PETM, late Maastrichtian, and Cenomanian–Turonian OAE2 sections are thick and bear further investigation.