HOLOCENE SEDIMENT VOLUME DETERMINED BY GROUND-PENETRATING RADAR AND SIDESCAN SONAR IN MAINE, USA

Estimates of post-glacial sediment transport volume can be useful when investigating watershed-scale denudation in formerly glaciated landscapes. In New England, anthropogenic activities such as forestry, farming, and construction of transportation and water management infrastructure, have further altered the near-surface sediment record. Unfortunately, these surface dynamics are difficult to constrain, both in space and time. Rate analogs used to estimate erosion and deposition in New England have typically been derived from lake bottom sediment cores. Reliance on core records assumes that derived sedimentation rates are representative of rates across the broader lake-bottom, despite being only a single point measurement. Geophysical surveys suggest that this assumption can be highly erroneous and unrepresentative of the entire lacustrine geological record. Herein, we conducted ground-penetrating radar (GPR) and side-scan sonar (SSS) surveys of multiple lakes in Maine, which are representative of different basin types, to estimate sedimentation rates and volumes since Laurentide retreat. Subsequent age constraints from cores on multiple GPR-imaged horizons could be used to refine estimates of sedimentation rate change caused by evolving physical, biological, and chemical processes that control erosion, transport, and re-deposition. This presentation will provide a summary of GPR and SSS data collection methods, assumptions and limitations, structural and surficial interpretations, key findings from multiple lake basins, and the story they tell of upland denudation from the last deglaciation through human alteration of Maine.