Paper No. 5
Presentation Time: 4:20 PM
STRONTIUM ISOTOPE RECORD OF SEASONAL SCALE VARIATIONS IN SEDIMENT SOURCES AND SEDIMENT TRAPPING IN LOW-ENERGY, SUBTIDAL AREAS OF THE LOWER HUDSON RIVER ESTUARY
Strontium isotope (87Sr/86Sr) profiles in two sediment cores collected from two low-energy, subtidal harbor slips in the lower Hudson River estuary exhibit patterns of variability that suggest different sources of sediment to these sites over time. Evidence from sediment Sr/Ca ratio, rare earth element (REE), Fe, Mn, total organic carbon (TOC), and CaCO3 profiles at both sites suggests that the observed variability reflects differences in the relative input and trapping of fine-grained sediment from seaward sources vs. landward sources linked to seasonal-scale changes in freshwater flow. Trapped sediments are primarily derived from the same parent material but, during low (base) flow conditions, a higher fraction of mature material (resuspended sediment) from seaward sources deposits and accumulates. During high flow conditions, a larger fraction of immature, newly eroded basin materials are trapped. Results show that high-resolution, multi-geochemical tracer approaches using strontium isotope ratios can be used to distinguish sediment sources and constrain (quantify) seasonal scale variations in sediment trapping in dynamic estuarine environments. Low-energy, subtidal areas in estuaries serve as natural recorders of local, short-to-medium term sedimentary processes over seasonal-to-yearly time scales.