FORAMINIFERAL CONSTRAINTS ON VERY HIGH-RESOLUTION SEISMIC STRATIGRAPHY AND LATE QUATERNARY GLACIAL HISTORY, NEW-JERSEY CONTINENTAL-SHELF

Internal stratigraphy of a Late Quaternary sediment wedge on the New J ersey outer continental shelf has been investigated using regional and 3-D seismic surveys, sediment cores and foraminiferal biofacies analy sis. Results from the study help constrain Late Wisconsinan glacial/de glacial history in this area. Three major reflectors (channels, S and R) define 5 stratigraphic units: S1-modern sediments; S2-sands overlyi ng a channelized surface (Channels reflector); S3-muds, clays and sand y muds below the channelized surface and above reflector S; S4-an unsa mpled unit between reflectors S and R; and S5-sands underlying reflect or R, the fatter surface defining the base of the sediment wedge. Mult ivariate quantitative analysis delineates four major faunal groups cha racterizing these stratigraphic units. Faunal patterns are interpreted in terms of modern foraminiferal distributions, planktonic/benthic ra tios and faunal abundance patterns. Group A dominates units S2 and S5 and is characterized by Cibicides lobatulus and Cassidulina islandica. The fauna indicates middle neritic water depths, moderate to high cur rent energy, and moderate accumulation rates. Group B dominates unit S 3 (muddy unit) and is characterized by Elphidium excavatum s.l., Bucce lla frigida, Fursenkoina fusiformis and miliolid spp. This fauna repre sents an environment with no modern analogue on the New Jersey contine ntal shelf reflecting middle neritic, low-energy conditions and the ac cumulation of predominantly muddy sediments. Group C dominates the mod ern sediment veneer (unit S1), and its diverse fauna is consistent wit h modern faunal distributions and environmental conditions. Group D co nsists of a low-diversity fauna dominated by Fursenkoina fusiformis an d Nonionella sp., which characterizes a few samples in unit S3. Enviro nmental conditions are probably similar to those described for faunal group B. The distribution and interpretation of these faunas, combined with preliminary C-14 AMS dates, indicate that the Quaternary history of the outer-shelf sediment wedge involves a middle Wisconsinan uncon formity (R), overlain by an unsampled unit (S4) and several meters of mud (S3). This relationship may represent a middle Wisconsinan outwash event. The muddy deposit was later incised by the ''Channels'' horizo n, possibly reflecting the Late Wisconsinan maximum lowering of sea le vel. This horizon is overlain by sandy transgressive deposits associat ed with rising sea level, presumably during the Holocene.