BACKGROUND AND OBJECTIVES

This chapter is the site report for the Millville corehole (Fig. F1), the ninth 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) (Fig. F1). These three sites targeted Oligocene–Miocene sequences, trying to unravel Icehouse sea level changes (Miller and Mountain, 1994; Miller et al., 1996b, 1998a). Onshore drilling continued as part of Leg 174AX at

  1. Bass River, New Jersey (October–November 1996; Miller, et al., 1998b), targeting Upper Cretaceous to Paleocene strata poorly sampled during Leg 150X;
  2. Ancora, New Jersey (July–August, 1998; Chap. 1, this volume), an updip, less deeply buried Cretaceous–Paleocene section complimentary to Bass River;
  3. Ocean View, New Jersey, (September–October, 1999; Chap. 2, this volume), targeting upper Miocene–middle Eocene sequences;
  4. Bethany Beach, Delaware, targeting the thick Miocene sequences in the depocenter of the Salisbury Embayment (Chap. 3, this volume); and
  5. Fort Mott, New Jersey (October, 2001; Chap. 4, this volume), targeting the largely nonmarine Potomac Formation (Fig. F1).

In total, these previous boreholes recovered 9,313.65 ft (2838.8 m) from 11,382.5 ft (3469.4 m) drilled (recovery = 81%).

Despite the logistic and scientific success in onshore coring to date, there is a significant gap in our understanding of Upper Cretaceous "greenhouse" sequences. Drilling at Bass River provided thick Upper Cretaceous sequences (696.1 ft; 212.17 m), but the section suffered from diagenetic overprinting because of its deep burial (1956.5 ft; 596.34 m TD). Drilling updip at Ancora, New Jersey, recovered unaltered Upper Cretaceous sections that were dated using Sr isotopic stratigraphy (Miller et al., 2003, 2004). However, because of its updip location, the section at Ancora was deposited in paleodepths too shallow for sampling a few critical sections (e.g., the Cenomanian/Turonian boundary). In addition, Ancora provides our only well-dated Upper Cretaceous section and one or more additional sections are needed to verify the regional significance and global ages of these greenhouse sequences and attendant sea level changes.

We targeted two new sites located on a projected dip profile between Ancora and Bass River that should provide ideal settings for sampling Upper Cretaceous sequences. The first site is the subject of this report, Millville, New Jersey, where the top of the Potomac Group was estimated to be within the drilling capabilities of the USGS Eastern Earth Surface Processes Team (EESPT) Mobile B51 truck-mounted drill rig (1500–1600 ft; 457.20–487.68 m). This site was also chosen because of its critical location for sampling important aquifers and the absence of continuous core data from Cumberland County (Figs. F2, F3, F4, F5, F6, F7). To address these hydrogeologic objectives, NJGS paid for all drilling costs for the Millville borehole. The second site is located adjacent to the coastline at Sea Girt, New Jersey, along strike of Millville (Fig. F1). This site will be tied into a nearshore multichannel seismic grid collected in May 2003 by G.S. Mountain, N. Christie-Blick, S. Pekar, and others, allowing us to evaluate the geometry of Upper Cretaceous sequences. The Upper Cretaceous sections at Bass River, Ancora, Millville, and Sea Girt and their integration with seismic control should provide an unparalleled opportunity to evaluate and date Upper Cretaceous greenhouse sequences. The JOIDES Planning Committee (PCOM) and Science Committee (SCICOM) designated drilling at Bass River, Ancora, Ocean View, Bethany Beach, Fort Mott, Millville, and Sea Girt as ODP Leg 174AX.

Drilling at Millville will also provide needed constraints for confined aquifers and groundwater potential for the southernmost part of the state of New Jersey (Fig. F8), particularly Cumberland County. Groundwater is the primary means of water supply for Cumberland County (Cauller et al., 1999). The Kirkwood-Cohansey aquifer system, an unconfined aquifer, is the main source of water in Cumberland County. This aquifer is susceptible to water-quality problems including nitrate, radium, mercury, organic chemicals, and pesticides. As populations grow in the county, the need to understand the thickness, properties, and extent of deeper confined aquifers is essential for water resource planners. The Millville corehole was intended to target these deeper aquifers in Cumberland County.

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