SUBSURFACE DISTRIBUTION OF UPPER CRETACEOUS SEQUENCES AND FACIES OF THE NEW JERSEY COASTAL PLAIN

The Upper Cretaceous strata of the New Jersey Coastal Plain consist of largely unconsolidated fluvio-deltaic, marginal marine, and shelf sediments that unconformably overlie crystalline basement. This sedimentary section records the history of eustasy, tectonics, and sediment supply on the eastern margin of North America. In this study, thirteen transgressive-regressive Upper Cretaceous sequences were correlated across the New Jersey Coastal Plain from core and well log integration. Four continuously cored boreholes (Ancora, Bass River, Millville and Sea Girt, New Jersey) established a clear link between the identified sequences (based on lithology, biostratigraphy and Sr-isotope stratigraphy) and their respective gamma ray, resistivity, and spontaneous potential well log signatures. These recurring “coarsening-upwards” sequences (transgressive clays overlain by highstand silts and quartz sands) were mapped across the coastal plain using an additional 28 well logs from industry sources. Correlation of these sequences allowed for the generation of a series of 25 isopach maps that depict sediment thickness variations from the Cenomanian through the earliest Danian. Analysis of the subsurface distribution of these sequences: (1) identified the location and migration of key onshore depocenters through time; (2) evaluated the role of the paleo-Hudson and Delaware Rivers as primary sediment sources, with the Paleo-Delaware showing similarities to the modern Niger delta and the paleo-Hudson to the modern Rhone delta; (3) refined the understanding of deltaic depositional models for the Turonian-Coniacian Magothy Formation, members, and sequences; and (4) revealed two previously unrecovered Magothy sequences that extend across the northern New Jersey Coastal Plain. The geometry of Upper Cretaceous sequences implicates the underlying basement structure (the South Jersey High, Raritan and Salisbury embayments) as an important factor in margin deposition.