MULTIFACETED ANALYSIS OF DRIFT B, LAKE CHAMPLAIN

Two lacustrine sediment drifts were located in Lake Champlain. Sediment drifts contain a nearly continuous sediment record, therefore providing significant paleoclimate data, which has been utilized in marine environments for decades. With few documented lacustrine sediment drifts, these Lake Champlain datasets will contribute new paleoclimate data for the lacustrine environment and continental North America. Drift B was studied in the summer of 2011 using a Compressed High Intensity Radar Pulse survey of 28 seismic lines, four piston cores, and five subsurface moorings equipped with Acoustic Doppler Current Profilers (ADCPs), temperature sensors, sediment traps, and Laser Suspended Sediment Sensors (LISSTs). Drift B is located atop a structural high and classified as a detached elongate drift. The sedimentation rates range between 0.10-0.13 cm/yr utilizing sediment trap accumulations. When compared to the thickness found by the seismic profile, these sedimentation rates, along with published sedimentation rates of 0.15 cm/yr, give an age range of 8,200-12,600 years for Drift B. The LISSTs recorded higher volumes of sediment and finer grains on the west side of the drift, as compared to the east. This sediment distribution is potentially due to high velocity currents recorded on the east side of the drift (maximum: 54.6 cm/s). The center of the drift had the lowest maximum velocity (35.8 cm/s), making it conducive to sedimentation. Velocity differences across the drift are explained by impingement due to bathymetric highs north of the drift. The sedimentation within Drift B provides information on the past 8,700 years of Lake Champlain’s climatic history and provides a baseline from which to examine current and future climate changes.