A CHRONOLOGY OF PLIOCENE SEA-LEVEL FLUCTUATIONS - THE UNITED-STATES MIDDLE ATLANTIC COASTAL-PLAIN RECORD

The sequence of marine and marginal-marine silts and sands of the U.S. Middle Atlantic Coastal Plain preserves a relatively complete record of Pliocene sea-level highstands. A general chronology for the deposition of these units has been developed previously from studies of the microfossil biostratigraphy complemented by a limited number of paleomagnetic and radiometric dates. Within this broad temporal framework it is currently difficult to assign ages to individual transgressive events with a resolution much better than 0.5 Ma. The age model proposed here attempts to refine the depositional history of the Atlantic Coastal Plain by correlation with the more continuous deep-ocean record. The model assigns probable ages to the Pliocene transgressions onto the Atlantic Coastal Plain based on evidence for sea-level highstands inferred from high-resolution deep-ocean delta-O-18 records. At least five major transgressive-regressive events can be correlated with presumed eustatic fluctuations. The temporal resolution for the timing of the transgressive events is greatly improved over that of the biostratigraphy alone. Many aspects of the proposed chronology require verification by more detailed field study, but it is offered as a testable working hypothesis.