SEDIMENTOLOGICAL RECORD OF FLOODING IN THE WESTERN MOHAWK VALLEY RECORDED IN AN OX BOW LAKE NEAR UTICA NEW YORK

Records of past climate can be acquired from numerous proxies such as ice cores, corals, and lake and ocean sediments, all which show that climate has fluctuated over the past millennia. Predictions of changes in the frequency and severity of flooding in response to human-induced climate change require that we develop accurate records of prehistoric flooding from natural archives. Sediment cores from floodplain lakes can provide continuous, high-resolution, and radiometrically-dateable archives of flooding that span centuries to millennia. This study is focused on the record of flooding in the upper (western) Mohawk Valley in central New York State. In March 2014, we extracted an ~3-meter-long core from a small (~0.40 km²) ox-bow lake near Utica NY (43.1064°N; 75.1901°W; 120 m asl) that is hydrologically connected to the Mohawk River. Cores were acquired with a Livingstone square-rod piston corer from an inflatable raft. Cores were split, described and analyzed for total inorganic carbon (TIC), total carbon (TC), magnetic susceptibility (MS), biogenic silica (bSiO₂), and major element composition. Flood events are recorded as laminae that are high in MS and Ti, and have low concentrations of organic carbon and bSiO₂, whereas the opposite is true of non-flood derived sediment. Accordingly, flood laminae dominate the basal 100 cm of the core and are overlain by approximately 125 cm of non-flood sediment. Much of the upper 75 cm of the core is dominated by multiple flood layers. Unlike cores from the lower Mohawk Valley, this core does not contain flood laminae associated with Hurricane Irene (29-30 August, 2011). Sediment cores from floodplain lakes in the western Mohawk Valley primarily record floods associated with snowmelt events whereas those in the eastern Mohawk Valley record tropical storms that impact the Catskill region and Schoharie Valley. The combination of records from the eastern and western Mohawk Valley can be used to delineate the history of snowmelt floods from floods triggered by tropical storms.