Methane in massive ice beds in Eastern Chukotka as an indicator of their origin

The study of massive ices is of interest both for the purposes of paleogeographic reconstructions, and for solving engineering and geocryological problems. Despite the widespread distribution of massive ice beds in the cryolithozone, the problem of spatial identification of them and mapping has not yet been resolved, which is mainly due to the difficulty of determining and understanding the processes of their formation. The paper presents the results of studying the methane content as a genetic trait in massive ice beds along the coast of Eastern Chukotka. In 2016–2022, our team studied variations in the methane content in 4 massive ice beds and host deposits using the “headspace” method. The CH₄ concentration in ice and air bubbles ranged from 1 to 1582 ppmv, which made it possible to suggest the genesis of each bed and compare it with previously proposed hypotheses of their formation based on the earlier made cryolithological and oxygen isotope analyses. The study has confirmed the intra-ground (median methane concentration of 432 ppmv) and buried (2 ppmv) genesis for two beds. For the third one, the issue of its genesis remained debatable, and in the fourth bed, the obtained results have thrown doubt on the previous hypothesis about the intra-ground genesis of ice, since the recorded methane concentration was found to be close to the atmospheric one. Despite the limitations of the “headspace” method shown in the paper, it was manifested as the adequate way for the field studies when transportation of frozen samples to the laboratory is impossible.