GEOLOGIC MAPPING OF MIOCENE TO PLEISTOCENE PALEOCHANNELS ACROSS THE MID-ATLANTIC COASTAL PLAIN REGION: RECORD OF SEA LEVEL, PALEOCLIMATE, AND STRUCTURAL INFLUENCES
Pliocene paleochannels vary from broad (1.6-2.2 km) and shallow (up to 15-m-deep) with outwash or braided river fluvial coarse arkosic sand and gravel fills (Pensauken and Beaverdam Fms.) to broad (~1.5-2.5 km) and deep (up to 70-m) with regressive fluvial sand and gravel fills overlain by transgessive-highstand estuarine-clay, silt, and sand to occasionally open bay to marine deposits with dinoflagellates, diatoms, and silicoflagellates (Kent Island Fm.). The Exmore paleochannel (paleo-Susquehanna) has a cosmogenic burial isochron age (~1.7 Ma) derived from basal gravels. Microflora and fauna provide depth of incision ages.
The age and location of individual paleochannel systems reflects the interplay of the following regional-to-local variables: tectonic influences that affected location of sediment source (uplift-erosion Appalachian Mountains) and drainage patterns (including fluvial meander bends); sea level (tied to climate and tectonics, effects base-level, erosion, deposition); and climate which includes glacioisostatic driven subsidence-deposition across the proposed glacial bulge area and beyond. These paleochannels preserve sea-level and paleoclimate data that provide constraints on the timing and magnitude of glaciations and are essential to unraveling the subsidence and sea level oscillation record of the past and provide potential possible insights into the future.