Structural and textural features of genetic types of the massive and ice wedges, and the conditions of their formation in the lower reaches of the Gyda River

Abstract

In the structure of the frozen thickness of the 2nd lake-alluvial terrace of the Gyda River were detected polygonal-wedge, lens massive and lensoid ice were. A detailed analysis of structural and textural peculiarities in the layers was carried out for the first time for these morphological types of underground ice. Based on the cryolithological structure of host rocks and structural-textural features of ice, the main mechanisms of deposit formation – polygonal-wedge, infiltration-segregational, and congelation were determined. The development of polygonal-wedge ice occurred in an alluvial floodplain setting of sedimentation accompanied by the climate fluctuations in the end of the Late Pleistocene and Holocene. The growth of ice wedge in the second half of the Sartan Period was interrupted under the reservoirs with shallow talik waters, after freezing of which there formed infiltration-segregational lensoid formation ices. The structure of frozen thickness was complicated by the lenses of congelation ice formed in thermoerosive niches in the Holocene optimum of about 6.5 thousand years ago. At the present time is possible the formation of similar types of ice on various sections of the relief. The established peculiarities of cryogenic structure are important for the creation of paleogeographic reconstructions and forecasting the dynamics of permafrost-facies environments accompanied by the modern changes in the depth of the seasonal thaw layer and the development of thermokarst.