This chapter is the site report for the sixth continuously cored and logged borehole drilled on the New Jersey Sea Level Transect. The JOIDES Planning Committee and Science Committee endorsed onshore drilling as an ODP-related activity. The first three sites (Fig. F1) were drilled at Island Beach (March-April 1993), Atlantic City (June-August 1993), and Cape May (March-April 1994) as Ocean Drilling Program Leg 150X (Miller et al., 1994a, 1994b, 1996a), the landward continuation of slope drilling by ODP Leg 150 (Mountain, Miller, Blum, et al., 1994). ODP Leg 174A continued the transect by drilling on the shelf (Fig. F1) (Austin, Christie-Blick, Malone, et al., 1998). Drilling continued onshore as Leg 174AX at Bass River (October-November 1996) (Miller, Sugarman, Browning, et al., 1998), Ancora (July-August 1998) (Miller et al., 1999b), Ocean View, New Jersey (September-October 1999), and Bethany Beach, Delaware (May-June 2000) (Fig. F1). Bass River and Ancora were drilled updip, targeting Upper Cretaceous to Paleogene strata, whereas Ocean View and Bethany Beach were drilled downdip, targeting younger strata. Onshore drilling of the Legs 150X and 174AX boreholes was sponsored by the National Science Foundation, Earth Science Division, Continental Dynamics, and Ocean Drilling Programs, and the New Jersey Geological Survey (NJGS).
The New Jersey Sea
Level/Mid-Atlantic Transect was designed to document the response of passive
continental margin sedimentation to glacio-eustatic changes during the Oligocene
to Holocene "Icehouse World," a time when glacioeustasy was clearly
operating (see Miller and Mountain, 1994, for summary). Legs 150X (coastal
plain) and 150 (slope) were extremely successful in dating Eocene-Miocene
sequences, correlating them to the 
18O
proxy for glacioeustasy and causally relating sequence boundaries to
glacioeustatic falls (Miller et al., 1996b, 1998). Onshore drilling was also
designed to evaluate mechanisms for sea-level change during the Late Cretaceous
to Eocene, an interval that purportedly lacked glacio-eustatic changes (e.g.,
Sea-Level Working Group, 1992) (see Miller et al., 1999a, for discussion).
The Ocean View borehole
targeted middle Eocene though Miocene sequences to document their regional
distribution and in particular, to verify the ages and significance of several
sequences that were sampled only at one previous borehole. For example, the Cape
May borehole provided the key section for Miocene sequence stratigraphic and 18O
comparisons (Miller et al., 1997) but three Miocene sequences have been
recognized only at this site (Sequences Kw1c, Kw2c, and Kw-Cohansey) and their
regional significance is uncertain. In addition, de Verteuil (1997) used
dinocysts to identify one additional upper middle Miocene sequence (Ch2) and
four upper Miocene sequences (Ch3-Ch6). These upper middle to upper Miocene
sequences have been identified only at the Cape May borehole, and additional
sampling is required to establish their regional significance.
Drilling at Ocean View and Bethany Beach was devised specifically to differentiate among potential controls on sequence distribution. The Ocean View and Bethany Beach boreholes and other onshore records (Fig. F1) provide an extensive regional database of Oligocene-Miocene sequences that can be integrated with nearshore seismic profiles (Fig. F1) (Monteverde et al., 2000). This regional view will allow mapping of regional depocenters and delineation of tectonic features (e.g., faults and differential basin evolution) and their effects on sediments. For example, the regional depocenter shifted from New Jersey during the early Miocene to Maryland (Owens et al., 1988) during the middle Miocene to Pliocene, whereas Oligocene strata show a remarkably "patchy" regional distribution (Pekar et al., 2000). Owens and coauthors (e.g., Owens and Sohl, 1969; Owens et al., 1997) argued that the Miocene pattern reflected differential warping on the basins and arches on the Atlantic continental margin, although the pattern could be ascribed to switching of sediment lobes. Similarly, the patchy regional distribution of Oligocene strata in the mid-Atlantic region have been attributed to lobe switching (Miller et al., 1997), faulting (Benson, 1994), or clinoform progradation (Pekar et al., 2000).
Drilling at Ocean View was also designed to test models of sedimentation within sequences, integrating borehole facies information with seismic facies information derived from seismic profiles collected on the continental shelf (Monteverde et al., 2000) (Fig. F1). Drilling at Bethany Beach, Cape May, Ocean View, Atlantic City, and Island Beach provides an along-strike view of numerous lower Miocene sequences that reach their maximum thickness and development in nearshore profiles (Monteverde et al., 2000). New seismic ties (Ch0698 profiles) (Fig. F1) allow direct correlation of ages and depositional environments to the nearshore grid. The boreholes also provide information on middle Miocene sequences that can be tied to the middle shelf where they are best developed (e.g., Mountain, Miller, Blum et al., 1994; Austin, Christie-Blick, Malone, et al., 1998).
The Ancora, Bass River, and Ocean View boreholes had another major objective: to evaluate the stratigraphic continuity and hydrogeological potential of aquifers and confining units. The NJGS funded direct drilling costs for Bass River and partially funded drilling at Ancora and Ocean View to address hydrogeological objectives. Bass River and Ancora targeted Cretaceous aquifers in the Mount Laurel, Englishtown, and Potomac-Raritan-Magothy (PRM) Formations (see Zapecza, 1989, for discussion of these aquifers). Ocean View targeted Miocene aquifers (e.g., the Atlantic City 800-ft sand aquifer of Zapecza, 1989) and confining units between Cape May and Atlantic City. Continuous coring in the New Jersey Coastal Plain has shown that aquifer-confining unit couplets are sequences bounded by unconformities (Sugarman and Miller, 1997). Thus, sequence stratigraphy provides a means to predict the continuity and regional distribution of aquifer-confining units (Sugarman and Miller, 1997). However, the updip-downdip and along-strike relationships of aquifer-confining units is not clear in many cases. For example, the Atlantic City 800-ft sand near Atlantic City is comprised of two sand bodies that make up the highstand systems tracts of Sequences Kw1a and Kw1b (Sugarman and Miller, 1997). However, at Cape May, there are three sand bodies that could be mapped as the Atlantic City 800-ft sand. The highest of these aquifer sands is associated with Sequence Kw1c and pinches out between Cape May and Atlantic City. Although this aquifer does not correlate with the Atlantic City 800-ft sand at Atlantic City, it has been mapped as its equivalent throughout the Cape May peninsula. Drilling at Ocean View was designed to answer outstanding questions about Cenozoic aquifers, including the Atlantic City 800-ft sand.
