Inactive and relict rock glaciers of the Deboullie Lakes Ecological Reserve, northern Maine, USA AARON E. PUTNAM 1 * and DAVID E. PUTNAM 2 1 Department of Earth Sciences and Climate Change Institute, University of Maine, Orono, Maine, USA 2 School of Science and Mathematics, University of Maine at Presque Isle, Presque Isle, Maine, USA Putnam, A. E. and Putnam, D. E. 2009. Inactive and relict rock glaciers of the Deboullie Lakes Ecological Reserve, northern Maine, USA. J. Quaternary Sci., Vol. 24 pp. 773–784. ISSN 0267-8179. Received 28 May 2008; Revised 20 November 2008; Accepted 23 November 2008 ABSTRACT: Lobate talus slopes in the Deboullie Lakes Ecological Reserve (DLER) of northern Maine exhibit parabolic profiles characteristic of inactive and relict talus-derived rock glaciers. Vegetated rock glacier surfaces suggest that the landforms are no longer active, and lobes comprising two DLER rock glaciers document periods of past growth. Observations of perennial subsurface ice are supported by datalogger temperature measurements, indicating that sporadic permafrost exists throughout the DLER. We compare the DLER rock glaciers, along with similar features elsewhere in New England and adjacent Que ´bec, to the modern alpine permafrost distribution. Results indicate that a mean annual temperature cooling of 68C is required to promote active rock glacier growth. Ages of plant remains recovered from the basal sediments of a local pond constrain deglaciation to before 11 320 14 C a BP, and core stratigraphy and organic content reveal that a periglacial environment persisted during the early postglacial era. Thus, we hypothesise that the DLER rock glaciers were active during Lateglacial time despite the lack of glacier activity in the region. We take this to suggest that north-eastern US rock glaciers formed in response to mean annual temperatures skewed towards the frigid winters of the Younger Dryas chronozone. Copyright # 2009 John Wiley & Sons, Ltd. KEYWORDS: rock glacier; talus; permafrost; Lateglacial; New England. Introduction Relict permafrost-related landforms, particularly permafrost- derived rock glaciers, have become important tools for decip- hering the climatic manifestation of the abrupt climate changes of the last deglaciation (Kerschner, 1978; Sailer and Kerschner, 1999; Paasche et al., 2007). At present, active rock glaciers are typically associated with rugged glacial and periglacial land- scapes where the climate maintains air temperatures suffi- ciently low to sustain continuous permafrost (Wahrhaftig and Cox, 1959; Barsch, 1996; Humlum, 1998). Most active rock glaciers occur at sites where mean annual air temperature (MAAT) is less than 48C (Humlum, 1998; Paasche et al., 2007). Therefore, inactive and relict (or ’fossil’) rock glaciers can be used to reconstruct previous episodes when the MAAT was favourable for active rock glacier growth. Rock-glacier- inferred MAAT can also complement summertime temperature proxy records, such as those based on glacier behaviour and palaeo-snowlines, to gauge the seasonality associated with past climate changes (Kerschner, 1978; Denton et al., 2005). The north-eastern USA and adjacent Canada form the western boundary of the North Atlantic, and is an important region for tracking the spatial influence of Lateglacial abrupt climate events that are thought to have originated from rapid changes in the North Atlantic thermohaline circulation (e.g. Broecker, 1998; Alley, 2000). Although much research has focused on the Lateglacial history of relict rock glaciers in Europe, there is a paucity of recent information from the north- eastern USA. In this study, we document previously unrecog- nised relict and inactive permafrost-derived rock glacier landforms in the remote Deboullie Lakes Ecological Reserve (DLER) of northern Maine, north-eastern USA (Fig. 1). Several talus slopes located in the DLER have the characteristic lobate topography of landforms that are variably defined as ’protalus lobes’ (White, 1976; Washburn, 1980; Harrison et al., 2008), ’lobate rock glaciers,’ (Wahrhaftig and Cox, 1959), ’talus glaciers’ (Smith, 1973), ’talus-derived rock glaciers’ (e.g. Kirkbride and Brazier, 1995; Brazier et al., 1998; Ikeda and Matsuoka, 2002) and ’valley-wall rock glaciers’ (e.g. Millar and Westfall, 2008). Over the course of four field expeditions conducted between 2004 and 2007, we carried out topographic surveys, temperature datalogger measurements and geomorphic mapping to describe these landforms and determine possible linkages to present and past climate. In addition, a new radiocarbon-dated lacustrine record of sedimentation and organic content affords insight into the timing of deglaciation, the age of rock glacier initiation, and the potential environ- mental conditions that may have accompanied rock glacier formation. The rock glaciers of the north-eastern USA and adjacent Canada offer important regional palaeoclimatic JOURNAL OF QUATERNARY SCIENCE (2009) 24(7) 773–784 Copyright ß 2009 John Wiley & Sons, Ltd. Published online 17 February 2009 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jqs.1252 * Correspondence to: A. E. Putnam, Department of Earth Sciences and Climate Change Institute, University of Maine, 228 Bryand Global Sciences Center, Orono, ME 04468, USA. E-mail: aaron.putnam@umit.maine.edu