Nesbitt, Ian M.; Campbell, Seth; Arcone, Steven; Smith, Sean MC
Geological Society of America Abstracts with Programs (2017)doi: 10.1130/abs/2017AM-306235
Post-Laurentide Ice Sheet erosion and re-deposition has had a significant influence on the geomorphology of New England. Anthropogenic activities such as forestry, farming, and construction of infrastructure such as dams and associated lake reservoirs, have further contributed to near surface changes. Unfortunately, these surface dynamics are difficult to constrain, both in space and time. One analog that can be used to estimate erosion and deposition, lake basin sedimentation, is typically derived from lake bottom sediment core samples. Reliance on core records assumes that derived sedimentation rates are representative of the broader watershed, despite being only a single point measurement. Geophysical surveys suggest that this assumption can be highly erroneous and unrepresentative of an entire lake basin. Herein, we conducted ground-penetrating radar surveys of multiple lakes in Maine, New Hampshire, and Vermont which are representative of different basin types to estimate sedimentation rates 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 data collection methods, assumptions and limitations, structural interpretations, and key findings from multiple lake basins in New England. Results show that GPR is an efficient, cost effective, and relatively accurate tool for helping to constrain lake erosion and deposition.
Although we don't know exactly what it looked like in the past, New England looks much different now than it did prior to the last glacial period. Human activities such as farming, logging, and construction of dams and lake reservoirs have also had aextensive impact on the earth's surface. However, it is difficult to know exactly how different the earth's surface looks as a result of these changes. One analog that can be used to estimate rates of change is lake basin sedimentation, which is typically calculated using material from the bottom of lakes. The method for getting this material, called coring, is an imperfect snapshot of a single point in a lake's often-complex sedimentary structure. Geophysical surveys suggest that sediment cores can be unrepresentative of sedimentation across an entire lake-bottom. In order to establish an idea of sediment structure and volume in New England since the last glacial period, we conducted ground-penetrating radar surveys of multiple lakes with different basin types in Maine, New Hampshire, and Vermont. This presentation provides a summary of GPR data collection on lakes, assumptions and limitations, structural interpretations, and key findings from multiple lake basins in New England. Results show that GPR is an effective way to help constrain sediment deposition volume and structure.