Foraminiferal implications for the formation of New Jersey shelf sand ridges

To investigate the genesis and evolution of New Jersey shelf sand ridges, foraminiferal assemblages were collected by vibracoring four shelf sand ridges (shoreface-attached, inner-shelf mid-shelf deeper mid-shelf). Stratigraphic units delineated by seismic and sedimentologic data can also be recognized micropaleontologically. However individual stratigraphic units recognized in, the four ridges are shown via multiple discriminant analysis to vary from ridge to ridge based on their foraminifera-the foraminifera show greater inter-ridge variation than the sedimentologic/seismic units. For example, a Holocene back-barrier unit shows significantly more marine influence in ridge 3 (deeper-mid shelf) than in ridge 2 (mid-shelf). Similarly, swale/inlet fills in ridges 1B (shoreface-attached), 1A (inner shelf), 2 and 3 show considerable foraminiferal variation due to variable mixing of back-barrier and open. marine faunas. Comparison, of foraminiferal assemblages from the upper parts of vibracores with those of surface samples from box-cores indicates taphonomic loss of the more delicate specimens. However after taking taphonomic loss into acount, the foraminiferal assemblages in surface sand are essentially identical to those in the underlying ridge sands which differ from ridge to ridge. Thus the ridge sands reflect time-averaged reworking. The foraminiferal data most closely support the hypothesis that ridge sand; accumulated in a nearshore setting but was significantly reworked by inner to mid-shelf processes during the Holocene transgression.