GLACIOLACUSTRINE AND HOLOCENE STRATIGRAPHY OF RANGELEY LAKE, MAINE

The stratigraphic record of paraglacial lakes provides detailed information on paleoenvironmental changes and potentially their climatic origins. Lakes are ideal for paleoecological analysis because their sediments are generally undisturbed and contain continuous stratigraphy with proxies such as fossils that record syndepositional climate conditions. Determining rates and intensity of global climatic changes due to natural and recent human influences requires widespread analysis of these and other proxy records. In addition, characterization of the lake floor is of use to fisheries biologists and other users. Stratigraphic and geomorphologic investigations at Rangeley Lake, western Maine aim to elucidate a past lake-level change timeline and to isolate potential mechanisms driving these climate changes. Digital sidescan sonar was used to image the morphology and composition of the lake bottom, showing deep basins, bedrock outcrop, extensive till and wave-washed bottoms, and sandy coves. Springs are present in the muddy basin floors. High-resolution boomer seismic reflection profiles reveal stratigraphy of the lake from patches of till, ubiquitous glaciolacustrine draping deposits, basin muds, and sandy shallow-water deposits. Geophysical results show submerged former shorelines, possibly indicating a drier period during the Holocene. Complementing the geophysical data are four sediment cores. Radiocarbon dating of the four cores yields timing of shoreline emplacement and sediment accumulation rates. Preliminary results indicate ages of 10,450 ± 80 ¹⁴C yr BP immediately above the glacial lacustine surface, and estimated accumulation rates of 0.126 mm/yr.