Sedimentary architecture and accumulation rates of two lakes in Maine

Nesbitt, Ian; Campbell, Seth; Arcone, Steven; Smith, Sean; Koffman, Bess

From the abstract: "The sedimentary architecture of lakes in previously-glaciated landscapes records geomorphological history that can shed light on the nature of late-glacial, periglacial, postglacial, and anthropogenic landscape change. Unfortunately, the sedimentary architecture of most lakes is not well understood, since they are most often studied using point-source sediment collection. Maine's lakes are especially interesting given the wide variety of geologic settings they encompass, particular among them the influence of lowland postglacial marine transgression. We conducted ground-penetrating radar (GPR) and side-scan sonar (SSS) surveys of multiple lakes in Maine, including The Tarn in Acadia National Park, representative of different basin types and landscape histories since the retreat of the Laurentide Ice Sheet. Combined with coring, the results suggest very slow (on the order of 0.1 m / kyr) accumulation over the majority of the Holocene north of the marine transgression, faster accumulation south of the transgression, and on the order of 100 m / kyr over the last century in some disturbed areas like The Tarn, likely related to farming, logging activities, construction, and increased trap efficiency of reservoirs due to dam emplacement. Geophysical results suggest accumulation may also have been faster in the late-glacial and periglacial periods, though the age and duration of these periods are difficult to constrain without further coring and geophysical work. Maines many lakes and ponds likely provide a buffer to sediment and solute transport from inland to coastal areas. This presentation will summarize GPR, SSS, and core collection methods, assumptions and limitations, structural and surficial interpretations, and key findings including accumulation rates and implications for historic and prehistoric landscape change."