Propositions for the legend of a map showing the distribution of fossil periglacial phenomena as evidence for permafrost at the maximum of the last glaciation

Abstract

An annotated legend for a map at the scale of 1 : 1,000,000 showing the distribution of fossil periglacial forms and structures indicative of permafrost during the maximum of the last glaciations is presented. It is the result of proposals made by the authors and discussions among members of the IGU Working Group: Coordination of Periglacial Research in collaboration with the INQUA Commission for the Palaeogeographic Atlas of the Quaternary. The background of the legend is shortly summarized in the introduction.

In the annotations the general content of the map and criteria concerning the compilation of the map are discussed: the legend is based on the opinion that out of the whole range of fossil periglacial phenomena only ice-wedge casts, fossil sand wedges, deep fossil frost cracks, pingos and pingo-like scares and fossil permafrost depressicms are reliablee indicators of former permafrost. Other fossil periglacial structures as e. g. fossil ground wedges, sorted forms, cryoturbations and involutions are regarded as unreliable indicators of former permafrost and plotted on.the map only on special condiions. Geomorphological forms (e. g. dry valleys, cryoplanation terraces) which are less well suited for palaeoclimatic reconstructions or whose formation does not necessarily require permafrost are not plotted on the map.

Recommendations are being made as to how to key the plotted features to specific references from which they are taken and with regard to an annotated list of graphical representations accompanying the map and showing in which way the plotted features are indicating permafrost during the maximum of the last glaciation.