Depositional sequences in the Cretaceous post-rift sediments on the New Jersey Atlantic margin

Abstract

Deposition of the Cretaceous post-rift sediments of the New Jersey Atlantic margin was controlled by numerous cycles of sea-level change. The strata deposited within each cycle constitute the depositional sequence of the cycle. Two types of deposits are identified in the depositional sequences of the New Jersey coastal plain, transgressive deposits and highstand deposits. The transgressive deposits formed when sea level was rising at its greatest rate, which led to rapid inundation of the margin. The highstand deposits formed when sea-level rise slowed and began to fall. Unconformities developed in the coastal plain during lowstand of sea level at the end of a cycle and during the initial slow rise of sea level at the beginning of the next cycle. As a consequence, the depositional sequences are unconformity bounded and are separated by hiatuses of varying time dimensions. In the coastal plain the transgressive deposits are characterized by their fine-grained nature and by containing authigenic glauconite, often in abundance. They have sharp basal contacts where they unconformably overlie a lower sequence. The highstand deposits are sands and silts that grade from the underlying transgressive deposits. Nine depositional sequences are recognized in the Lower and Upper Cretaceous on the basis of these criteria. Each of these sequences is time constrained by biostratigraphic distribution of various microfossil groups (foraminifera, pollen and spores, dinoflagellates, and coccoliths). An additional four depositional sequences are suggested in the non-marine Lower Cretaceous on the basis of the interpretation of highstand deposits. Two major unconformities, five minor unconformities, and their accompanying hiatuses are recognized. A major Coniacian to early Santonian hiatus can be traced from the coastal plain to wells in the Baltimore Canyon Trough.