PALEOCHANNEL INCISION AND INFILL ON THE NEW JERSEY SHELF: TIMING, CHARACTER AND DEPOSITIONAL ENVIRONMENT
Major geologic features of the NJ shelf include a mobile, sandy surface layer, numerous shallowly buried paleochannels with associated infill and a time-transgressive regional unconformity (previously termed R). Three sites were drilled into the middle and outer NJ shelf to examine patterns of incision and infill. Site 1, in 130 m of water and penetrating the outer shelf wedge, shows that the upper ~1 m of the seafloor is actively being reworked (with C-14 ages ranging from modern to ~7kyrs). Age control indicates that sediments overlying R on the outer shelf wedge are ~30 to 40 K cal y BP and foraminiferal as well as sedimentological indicators suggest a marine environment, consistent with deposition during Stage 3. At sites 2 and 3 on the midshelf (~80 m of water), muddy sediments into which the channel is incised, whether above or below R are old, ~35-45K cal y BP. The timing of infilling is much later, ~14K cal y BP, constraining downcutting to between 3545K cal y BP and 14K cal y BP. This is consistent with a recent study indicating regional continental downcutting (Reusser et al., 2004) between 35 and 13-14 Ka. Foraminiferal and sedimentological evidence suggest that infilling with sea level rise was not a simple deepening depositional sequence from estuarine to open ocean conditions, but can be shown to have been a series of repeated depositional sequences, alternating between restricted, estuarine and open, inner-shelf environments.