CHARACTERIZING HOLOCENE SEDIMENT ACCUMULATION AND HUMAN IMPACTS IN AN UPLAND KETTLE POND IN EASTERN CONNECTICUT

Lakes contain valuable sedimentary archives that can be used to understand landscape and environmental change through time. Here, we present the results of a project focused on examining Echo Lake in eastern Connecticut. Echo Lake (elevation ~78 m) is a kettle pond located within the upper reaches of the Thames River watershed. It lies adjacent the Fenton and Mount Hope Rivers and lake levels are controlled by groundwater - there are no side streams flowing in and no dam. A high-resolution sonar scan of Echo Lake indicates that lake bathymetry is characterized by an elongated bowl shape, maximum water depths of 4.8-5.5 m, and steep edges. To characterize sediment in the lake, we collected 3 shallow surfaces cores ranging 65-90 cm in length, one deeper push core that recovered sediments lying ~1m to 5m below the sediment-water interface, and 10 lake bottom grab samples. The long core was sampled for ¹⁴C dating and all samples were analyzed for organic content (measure by loss-on-ignition) and heavy metals such as Pb, Zn and Cu (measured by handheld XRF). Surface and shallow cores highlight the influence of human activities, with high levels of Pb, Zn and Cu in all surface sediments and the uppermost 40 cm of sediment cores marking regional industrialization and other activities over the past 150 years. Deeper stratigraphy (>1 m) highlights a transition from high sediment input in the late Pleistocene/early Holocene to high organic input punctuated by small sand lenses inferred to reflect storms that mobilized sediment from nearby kettle walls into the deepest areas of the lake. The Holocene stratigraphy observed at Echo Lake reflects either a transition from colder environment to a warmer one that supported nearby lake vegetation, or shifting lake levels through time.