Paper No. 93-9
Presentation Time: 10:45 AM
DISTRIBUTION AND TENTATIVE AGES OF AN EXTENSIVE PALEOCHANNEL NETWORK OFFSHORE OF THE DELMARVA PENINSULA, U.S.A
Paleochannels are ancient fluvial beds that provide information on paleoclimate and continental shelf evolution. Here we present preliminary analysis of chirp and 16-channel boomer seismic reflection profiles, swath bathymetry, acoustic backscatter data and sediment samples collected in 2014 and 2015, from 5800 km2 of the inner continental shelf off the Delmarva Peninsula. A 3-km-spaced grid of seismic reflection profile data extending 30 km offshore coupled with a high-resolution (200-m spaced lines) nearshore survey resolve a series of large paleochannels 3-10 km wide, with bases occurring roughly between 50-70 mbsf. These infilled channels are interpreted as ancient courses of the Susquehanna River formed during times of major sea-level lowstands and are incised into Tertiary marine sediments. In addition to channels previously mapped by Colman et al. (1990) and Foyle and Oertel (1995) (i.e. Cape Charles, Eastville, and Exmore) we resolve at least two paleochannels within and just south of Chincoteague Bight trending east, south-east. These channels may be the offshore expressions of the Salisbury and Metomkin paleochannels, identified previously in boreholes collected beneath the present-day southern Delmarva Peninsula. These paleochannels and associated transgressive infills provide ample coring targets for sea-level indicators and are associated with modern inlets and erosional hotspots in the Delmarva Peninsula.