Late Weichselian permafrost distribution and degradation. A pingo based reconstruction for the Netherlands
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Permafrost was present throughout the Netherlands during the Late Pleniglacial. Evidence of this permafrost consists of several periglacial features of which pingo remnants are the most prominent. Permafrost distribution, minimum depth and characteristics of decay of permafrost throughout the Netherlands during the Weichselian Late Pleniglacial and the following Weichselian Late-glacial was reconstructed by information derived from pingo remnants. Relict pingos provide not only an indication of the (minimal) depth of former permafrost, but might also contain a unique lithological and botanical record of environmental change since the last deglaciation. While relict pingos are abundant in the northern Netherlands, few have been recognized in the southern part of the Netherlands. Based on Lidar indicated circular depressions, together with fieldwork in the area of Heeze-Leende, the presence of relict pingos in this region has been investigated. From a previously investigated relict pingo, Klein Hassels Ven, a new core was obtained in order to reconstruct regional environmental changes in the area since the Last Glacial Maximum. It is concluded that permafrost occurred throughout the northern, central and southern Netherlands during the Late Pleniglacial. Minimum depth of permafrost varied between 5m and 16 meters in the northern and middle Netherlands while permafrost depth was shallower in the southern part of the Netherlands, with a minimum depth of 2m to 5 meters. Southern Netherlands pingo remnants contain a comparable Late-glacial vegetation development as indicated by pingo remnants in the northern Netherlands. Based on the presumable hydraulic origin of the pingos throughout the Netherlands, permafrost is concluded to be discontinuous during pingo formation. Decay of permafrost in the Netherlands occurred simultaneously throughout the Netherlands due to climatic warming at the onset of GI-1e (correlating to Bølling), as indicated by the basal infill of the investigated pingo remnants.