TALUS-DERIVED ROCK GLACIERS OF THE DEBOULLIE LAKES ECOLOGICAL RESERVE, NORTHERN MAINE, USA

We present geomorphic evidence for talus-derived rock glaciers in the Deboullie Lakes Ecological Reserve (DLER), northern Maine, USA. Parabolic profiles, temperature dataloggers, vegetation cover, and perennial subsurface ice characterize a series of coarse talus accumulations in the DLER as inactive and relict rock-glacier forms representing periods of prior growth. Comparison to the modern alpine permafrost distribution indicates that a ~6°C mean-annual temperature lowering is required to promote active rock-glacier growth. AMS ¹⁴C dates from the basal deposits of a lake sediment core suggest that the DLER was free of glacial ice prior to the beginning of the Younger Dryas chronozone (YD). Taken together, we interpret these data to imply that DLER rock glaciers formed under periglacial environmental conditions of the late-glacial period.