Relict cryogenic structures in the landscapes of Orenburg region, Russia

Abstract The evidence of Neo-Pleistocene and possibly Holocene paleopermafrost was found in Orenburg region, Russia. Large polygons are clearly visible in relief, which indicate the existence of continuous low-temperature frozen rocks in the past. We found and studied the structure of the ground wedges formed in sediments of different composition and genesis. Ground wedges in loess-soil formations indicate several stages of permafrost expansion at the end of the Neo-Pleistocene. Freezing of ground was accompanied by the formation of polygonal-wedge ice and initially-ground wedges. During the warming periods the permafrost melted and pedogenesis restarted together with active thermokarst processes and formation of pseudomorphs along the wedge ice.