DECIPHERING COMPLEX DELTAIC AND NEARSHORE FACIES USING INTEGRATIVE SEQUENCE STRATIGRAPHY, MAGOTHY FORMATION (UPPER TURONIAN-CAMPANIAN), NEW JERSEY AND DELAWARE

Recent drilling at Sandy Hook and Sea Girt in Monmouth County, New Jersey has provided continuously cored, thick delta-plain and delta-front facies of the Magothy Formation (upper Turonian-Coniacian). The Magothy thickens northward across New Jersey (NJ) toward Long Island, with a large river source and a moderate tidal influence. The formation thins dramatically southward from this deltaic source toward Delaware, where some areas appear to be incised valley fill. The Magothy Formation is informally divided into 5 members and 4 to 5 sequences in NJ. Pollen is critical in correlating these units. These members/sequences can be mapped along strike and downdip throughout the NJ coastal plain, but are best expressed at Sandy Hook, where the Old Bridge and Sayreville Sand Members are thick and show evidence of high rates of deposition. The uppermost Magothy strata, the Cliffwood Beds, show the strongest marine influence with tidally influenced interdistributary bays and swamps in lower delta plain environments, less organic-rich interlaminated sandy clays deposited in delta front environments, and slightly sandy clays in marine/prodelta environments. The Morgan Beds consist of interbedded dark clay and micaceous fine sand deposited in subaqueous levees, interdistributary bays, and bay mouth bars. The Amboy Stoneware Clay was deposited in interdistributary bays and prodelta settings. The Old Bridge Sand was deposited in tidally influenced delta front environments and the South Amboy Fire Clay in lower delta plain (estuarine?) environments. The basal member, the Sayreville Sand, was deposited in fluvial environments and are excellent aquifer sands. The widespread distribution of Magothy sequences hints at the stability of deltaic depositional systems despite known variations in eustasy during the Turonian-Coniacian.