18.104.22.168. Periglacial features
Periglacial features are morphological features which are associated with continuous (permafrost) or discontinuous (diurnal or seasonal freezing) periods of sub-zero temperatures. Such features on which palaeoclimatic inferences can be based include: fossil ice wedges; pingos; sorted polygons; stone stripes; and periglacial involutions. Detailed descriptions of these features may be found in Washburn (1979). Unfortunately, palaeoclimate reconstructions based on such phenomena are subject to a fair degree of uncertainty. First, the occurrence of periglacial activity during the past can only indicate an upper limit on palaeotemperatures, not a lower one (Williams, R.B.G., 1975). Second, periglacial features are generally difficult to date accurately; dating of the sediments with which they are associated provides only a maximum age estimate.