ANNUAL LAYERS IN THE HUDSON RIVER

We have been studying a sediment core taken from the Hudson river just south of Piermont Marsh. The core, numbered LWB1-08, is kept at the Core Repository at the Lamont-Doherty Earth Observatory. ITRAX X-Ray Fluorescence (XRF) data showed large peaks in silica that corresponded with large erosional events in the core. XRF data also showed regular peaks in manganese, which we are fairly confident are annual, due to the redox-sensitive nature of manganese and the annual fluctuation of oxygen levels in the Hudson. A chronology based off of the manganese peaks from three XRF scans matched a large flood event in 1913. Lead data from the same XRF scans showed a sharp increase around the year 1860, according to our manganese chronology, which corresponds with when coal burning became especially prevalent in New York City and the surrounding Hudson River area. There was also a smaller lead peak in the early 1760’s, right near the bottom of the core. We will be inspecting samples from the bottom of the core for slag from coal burning to ensure that the lead reading is not a result of flow-in, or water rushing into the bottom of the core during extraction. We are waiting for results back from ¹⁴C dating and ¹³⁷Cs dating for added stratigraphic markers to confirm that our manganese-based chronology is accurate.