PLEISTOCENE CHANNELS ON THE NJ CONTINENTAL SHELF AS A RECORD OF REGIONAL UPLIFT AND SUBSIDENCE: INSIGHTS FROM 3D SEISMIC IMAGING

Previous studies have shown the stratigraphy of the New Jersey (NJ) continental shelf of eastern North America records Pleistocene changes in relative sea level driven by changes in global mean sea level, glacial isostatic adjustment (GIA), and mantle dynamic topography (MDT). Over the last six marine isotope stages (MIS 1-6; since ~185 kyr), the relative sea level on the NJ margin has varied by ~125 m. During periods of low relative sea level the margin was dominated by fluvial systems and widespread erosion; during periods of high sea level, barrier islands and estuaries were common. Complex interplay between these end-member regimes coupled with minimal accommodation space resulted in limited sediment accumulation over the past 185 kyr. This, combined with poor age control, makes it challenging to date and trace seismic surfaces across the margin. This study integrates existing high-resolution subbottom profiles and core data with a new 555 km² high-resolution 3D seismic survey (MGL1510) offshore NJ to investigate the relationship between channel development and regional processes of vertical motion of the crust associated with sea-level variability.

Previous studies have identified a Hudson paleochannel trending ~160º, significantly different from the ~120º trend of the modern Hudson Shelf Valley. We have examined the morphologies and trends of other paleochannels of the inner to mid-continental shelf to determine if regional processes (GIA and MDT) caused the shift. MGL1510 data show Pleistocene channel systems range from mature u-shaped to immature v-shaped incisions, associated with highly sinuous to straight fluvial systems respectively. We have measured incision depths during each identifiable lowstand (MIS’s 2, 4, and 6) to determine if they varied systematically across the margin as a function of proximity to the glacial front. We use the spatial distribution of relative incision depths at each of the glacial stages as control points to test GIA models where other controls are sparse.