Foraminiferal biostratigraphic data indicate that the stratigraphic history of the Upper Cretaceous rocks of the coastal plain of New Jersey can be considered in terms of four main depositional phases which in turn reflect major transgressive-regressive cycles.
The first depositional phase can be seen against the backdrop of the well-known Cenomanian eustatic rise of sea level. A new stratigraphic unit, the Bass River Formation, is proposed for the calcareous clayey silts deposited during this initial encroachment of the sea into the region. The Bass River Formation ranges in age from earliest Cenomanian (Washitan) to early Turonian (Eaglefordian), and contains the following planktonic foraminiferal zones: Rotalipora greenhornensis/Praeglobotruncana delrioensis Zone, Rotalipora cushmani Zone, and Marginotruncana helvetica Zone. Its age equivalents in outcrop are the upper Patapsco and Raritan Formations. The Bass River is restricted to the subsurface with only a marginal-marine facies in the Woodbridge Clay Member of the Raritan. This transgression apparently reached its climax in the early Turonian during which the Woodbridge Clay Member was deposited.
Phase two marks the only major regression in the coastal plain. The Sayreville Sand Member and the South Amboy Fire Clay Member of the Raritan were deposited during this phase which also is represented by a probable hiatus in which part of the Coniacian is missing. Toward the center of the Salisbury embayment continuous marine sedimentation took place.
During phase three another widespread marine transgression occurred in which the Merchantville and Magothy Formations were laid down. This transgression established the strandline for the deposition of subsequent Cretaceous units. The Woodbury Clay is the shoal facies which marked the end of this phase. The Merchantville in the subsurface contains the following early Santonian to early Campanian planktonic zones: Marginotruncana concavata Zone, Globotruncana fornicata Zone, and Archaeoglobigerina blowi Zone. The Woodbury contains part of the A. blowi Zone and the Ventilabrella glabrata Zone.
Finally, the oscillation of the shoreline during the late Campanian and Maestrichtian produced the familiar alternation of greensands (Marshalltown, Navesink, and basal Hornerstown), with regressive sand units (Englishtown, Wenonah-Mount Laurel, and Redbank-Tinton).