TECTONIC AND SEDIMENT SUPPLY EFFECTS ON EUSTATICALLY CONTROLLED SEQUENCES OF THE MID ATLANTIC REGION

Global sea-level change is a primary control on passive margin stratigraphy and sequences (unconformity bounded units) are the main product of eustatic changes. By analyzing sequences in New Jersey onshore coreholes, we developed a eustatic estimate for the past 100 m.y., documenting 18 Late Cretaceous and 33 Cenozoic sea-level fluctuations of 30-50 m. Our eustatic estimate was developed by: 1) dating sequences at 5 onshore New Jersey coreholes (ODP Legs 150X and 174AX); 2) estimating paleowater depth histories in the coreholes by integrating lithofacies and biofacies; and 3) backstripping the corehole records, progressively accounting for the effects of compaction, loading, and simple thermal subsidence. The backstripped records from the different coreholes yield similar sea-level estimates. These estimates agree with those derived from global oxygen isotopic records, suggesting we have produced a valid eustatic estimate. Superimposed on this global pattern are regional and local differences that are attributable to tectonic and sediment supply variations. Differences among sequences in Virginia, Maryland, Delaware, and the eustatic model developed in New Jersey reveal minor tectonic overprints: 1) relative uplift of 10's m occurred in Virginia and Maryland ca. 33-18 Ma; 2) relative subsidence of 10's m occurred in the Delmarva peninsula ca. 18-12 Ma; and 3) relative subsidence occurred in Virginia and Maryland ca. 8-2 Ma (Eastover-Yorktown time). Changes in sediment supply strongly influence sequences: 1) large river systems influenced New Jersey with deltaic deposits during the Cretaceous (120-71 Ma) and latest Oligocene-Miocene (27-14 Ma); 2) Delaware and Virginia/Maryland lack this strong influence during the Late Cretaceous and Miocene; 2) sediment starvation and pelagic sedimentation generally dominated much of the mid-Atlantic region from 71-27 Ma. As a result of the interaction of eustasy, tectonics, and sediment supply, aquifers in New Jersey occur are primarily Cretaceous (the “PRM”) and Miocene (Kirkwood) in age.