Periglacial Appalachia: palaeoclimatic significance of blockfield elevation gradients, eastern USA

• Published in: Permafrost and Periglacial Processes
• Main Authors: Kim J. Park Nelson, Frederick E. Nelson, Michael T. Walegur
• Format: Article in Journal/Newspaper
• Language: unknown
• Subjects: permafrost
• Online Access: https://doi.org/10.1002/ppp.574

Locational data for 96 allochthonous blockfields distributed throughout the Appalachian Mountains of eastern USA were obtained using TerraServer, an online resource for viewing air‐photo and satellite imagery. The elevation of Appalachian blockfields south of the Last Glacial Maximum (LGM) border parallels regional gradients of contemporary mean July, summer and annual temperature. Mean July temperature reductions inferred from palaeoecological studies indicate that the median elevation of blockfields throughout the Appalachians lay at or above timberline during the LGM. Palaeotemperatures calculated using known Appalachian lapse rates and published LGM temperature departures indicate that most blockfields in the study area were formed under climatic conditions conducive to permafrost. Allochthonous blockfields in the Appalachians appear to be constituent elements of periglacial ‘form communities’. Internet‐based map products can be used to create generalised reconnaissance‐level geomorphic data bases over large areas. Complementary use of these resources and spatial‐analytic techniques holds considerable potential for addressing the broad‐scale problems with which traditional climatic geomorphology is concerned. Copyright © 2007 John Wiley & Sons, Ltd.