A sedimentological study of the dredged material deposit in the New York Bight

Abstract

A variety of sediment types were identified in sediment cores taken at the dredged material dumpsite in the New York Bight. Black sandy mud is characteristic of dumped dredged material while glauconitic and quartzose sands are typical of the naturally deposited sediments underlying the deposit. The sedimentological investigation indicates that largescale differentiation of dumped material occurs at the dumpsite. Laminated sediments and discrete beds are typical of the central part of the deposit, the area that receives the bulk of direct dumping. Relatively homogeneous, fine-grained sediments, presumably derived from the area of direct dumping, are characteristic of the material present at the periphery of the deposit. Preferential transport of fine-grained material to the fringes of the deposit may be an important contaminant transport mechanism in the area. Incursion of glauconitic sand, derived from surrounding areas, onto the edges of the deposit is also believed to occur. Based on bathymetric surveys of the area conducted in 1936, 1973, and 1978, rates of dredged material accumulation at the dumpsite have been estimated for the period 1936–1978. The calculated rates range from 50 cm/yr at the apex of the deposit to 6 cm/yr at the periphery.