Periglacial landforms of Dartmoor: an automated mapping approach to characterizing cold climate geomorphology

Abstract

A systematic mapping approach characterizes Dartmoor periglacial landform signatures using the geomorphology of nine summit areas displaying well developed tor and blockfield landforms. This combines manual vectorisation with automatic classification and surface boulder identification, using spectral signatures to reveal patterns and distribution. Tors were classified using a three-fold scheme: T0 - summits with no tors; T1 - summits with castellated and high relief tors; T2 - summits with subdued or low relief tors. Clitter (blockfield and blockstream) features identified by automated mapping include boulder lobes and stripes and boulder-fronted lobes and terraces, arranged according to distance downslope from parent tors. This zonation of periglacial landforms is proposed as a landsystem signature for areas exposed to periglacial and permafrost processes for significant time during the Quaternary. It represents a process-form regime in which cold climate processes, acting on partially deeply weathered and pneumatolysised granite, produce castellated tors, cryoplanation benches and autochthonous blockfield (clitter), and permafrost creep develops boulder lobes that elongate and evolve downslope as allochthonous blockslopes with boulder stripes and boulder-fronted lobes and terraces. This demonstrates that automated mapping can be applied to areas of upland periglacial landforms to rapidly and systematically compile quantifiable patterns of landform assemblages.