COREHOLES PROVIDE GROUND TRUTH FOR THE HYDROSTRATIGRAPHIC FRAMEWORK OF THE CRETACEOUS POTOMAC-RARITAN-MAGOTHY AQUIFER SYSTEM OF THE NEW JERSEY COASTAL PLAIN

Coring New Jersey Coastal Plain (NJCP) sites by the United States Geological Survey Eastern Earth Surfaces Processes Team (Gene Cobbs, Gene Cobbs III, Jeff Grey, Don Queen, and Dennis Duty) has led to major advancements in our understanding of the hydrostratigraphy of the Potomac-Raritan-Magothy (PRM) aquifer system. Funding was provided by the New Jersey Geologic and Water Survey through Water Bond issues, the National Science Foundation, and the International Ocean Discovery Program (IODP) to support geologic mapping and hydrogeologic studies in New Jersey and IODP Legs 150X and 174AX. Beginning in October, 1984 at Mays Landing, NJ and concluding in October, 2014 at Sandy Hook NJ, approximately 23,000 ft (7 km) of continuous coring and logging was completed at 17 sites, providing in situ geologic material that significantly improved our understanding of the subsurface geology and hydrostratigraphy of the NJCP, including the age, depositional environments, geologic composition, extent and thickness of aquifers and confining beds.

The hydrostratigraphic framework of the largest aquifer in New Jersey, the PRM, was vastly improved with sampling and describing upper and lower delta-plain facies in Potomac Formation unit 1 (Barremian-Aptian), unit 2 (middle-late Albian), and unit 3 (early Cenomanian). Integration of pollen with sequence stratigraphic stacking patterns in cores and well logs provides a predictive framework suggesting surprising continuity of aquifer units deposited as fluvial sequences.

Pollen and nannofossils date the Magothy Formation as upper Turonian to Coniacian; integration of corehole and outcrop allow correlation of these lower delta plain, delta front, and prodelta facies. Mapping of the Magothy shows thickening northeastward across New Jersey toward Long Island, New York and thinning southwestward towards Delaware where estuarine environments are preserved only in incised valley fills. The widespread distribution of Magothy facies indicates stability and correlation of this modest-sized deltaic depositional system despite low-amplitude Turonian-Coniacian sea-level variations.