PLEISTOCENE AND RECENT DEPOSITIONAL ENVIRONMENTS OF THE NEW JERSEY MARGIN: PRELIMINARY RESULTS FROM LONG CORING

Sedimentation on the Pleistocene NJ margin is defined by glaciation. On the slope, where accommodation space is adequate for sediment accumulation, sediment physical properties vary with proxies for global sea-level change. Sediments deposited during Pleistocene glacial periods reflect the lower sea-level and proximal fluvial source and are recognized by the high content of sand, wood, and mica, and transported neritic benthic foraminifera. However, the pattern on the shelf is not as clear. On the modern shelf, sediments are dominantly relict, the region is incised by a complicated system of sediment- filled channels, and successive glacial events destroy previous events. Previous attempts at drilling continuous section through the highly variable lithology of the NJ shelf (e.g., ODP Leg 174A) have met with only limited success.

Long cores with good recovery were recently drilled on NJ shelf. Analysis of core-catcher samples from Site 2 (~80 m w.d.) indicates deposition varied between an inner – middle neritic paleoenvironment (Elphidium spp.), and an environment proximal to a fluvial source (pebbles, metamorphic rock fragments, abundant mica, and wood and shell fragments). The lithology is dominated by fine sands containing occasional shell hash. The sands near the base are inter-bedded with clays containing abundant pyrite, and wood and metamorphic fragments.

Site 1 (~129 m w.d.) lithology is dominated by stiff bioturbated clays, overlain by an uppermost unit of muddy sands containing shell hash. The clays yielded a diverse benthic foraminifera assemblage containing abraded likely transported miliolids as well rare sub-rounded quartz grains. Planktonic foraminifera include G. truncatulinoides and G. inflata, interpreted as a mixed interglacial and glacial assemblage. Site 3 (~76 m w.d.) is composed of three major lithologic units: an upper unit of thixotropic coarse shelly sands; a thick interval of stiff gray bioturbated muds with occasional sand lenses; and a lower unit of shelly sands. Shell lags bound the sands and clay layers. The lowermost shell lag correlates with a major regional seismic reflector (R). Elphidium spp. dominate the sandy unit, indicating a likely inner- middle neritic depositional environment. Foraminifera are absent when abraded shell material and large (>2 mm) pebbles are present.