DISCHARGE AND SEDIMENT TRANSPORT CHANGES IN THE HUDSON RIVER ESTUARY FROM 6,500 YEARS TO PRESENT

Paleosalinity estimates and rates of sedimentation inferred from cores taken in the Hudson River between Alpine, NJ, and Haverstraw Bay, NY, were used to constrain sediment transport in the Hudson River and climate variability for the Hudson River watershed during the past 6,500 years. Paleosalinity estimates were made by integrating several proxies: benthic foraminiferal biofacies and oxygen and carbon stable isotopes and Mg/Ca ratios from juvenile bivalves species, Gemma gemma. Carbon-14 age models were developed to evaluate the rates of deposition. Sediment transport and deposition patterns were based on sedimentation rates, grain size variability, and sedimentary structures.

Recent studies showed that bathymetric changes were minor within the segment of the Hudson River studied except on the western margins of the Hudson River, which experienced high rates of sedimentation. This zone of high sedimentation migrated seaward in the Hudson River during the last 5,000 years and is consistent with a paleo-expression of the Estuarine Turbidity Maximum (ETM). Paleosalinity estimates indicate a decrease between 4,000 and 2,500 years ago. Since salinity changes in the Hudson River are due to changes of fresh water into the river (i.e., river discharge), constraints can be made on climate variability of the Hudson River Watershed. These records suggest that summertime discharge in the Hudson River, which is influenced by precipitation rates, was lower during the period 6,500 to 4,000 years ago in the Hudson River.