GEOCHRONOLOGY AND SEDIMENTOLOGY OF THE LOWER PASSAIC RIVER, NEW-JERSEY

In an attempt to characterize localized rates of sediment accretion, 1 0 sediment cores were collected from the lower reach of the Passaic Ri ver, a major tributary of Newark Bay, New Jersey. Sediments were assay ed for Pb-210 activity at predetermined depths and the rate of sedimen t accretion (cm yr(-1)) was estimated from the least squares regressio n of the log of unsupported activity versus depth. Sediment accretion rates derived from Pb-210 measurements (R(Pb)) were used to predict th e depth interval within the core containing sediments deposited around 1954; subsequent Cs-137 analyses were focused on this depth interval. Sediment accretion rates derived from Cs-137 measurements (R(Cs)) wer e extrapolated from the depth of the 1954 horizon. Lead-210 derived se diment accretion rates in cores collected from a sediment bench extend ing along the inside bend on the southern shore of a meander in the ri ver, ranged from 4.1 cm yr(-1) to 10.2 cm yr(-1) and averaged 6.8 cm y r(-1). The R(Cs) estimates for cores from this area ranged from 3.8 cm yr(-1) to 8.9 cm yr(-1) and averaged 6.6 cm yr(-1). The R(Cs) for cor es collected in a more hydrologically dynamic reach of the river upstr eam of the sediment bench, were only 0.41 cm yr(-1) and 0.66 cm yr(-1) . The results of this investigation indicate that this reach of the lo wer Passaic River is an area of high sediment accumulation, retaining much of the sediment load deposited from upstream and downstream sourc es. The rates of sediment accretion in the lower Passaic River are amo ng the highest reported anywhere in the Newark Bay estuary.