Formation of the yamal crater in Northern West Siberia: Evidence from geochemistry

Abstract

In the framework of this work, studies on the Yamal crater formed as a result of a cryogenic eruption of a water-gas fluid were carried out. The structure and variations of the composition of the geochemical field along the section of the upper horizons of permafrost are considered on the basis of field work, including the drilling of boreholes near the crater. The obtained regularities of the distribution of chemical elements, and gases between the mineral component of the soil and meltwater, suggest that permafrost at the site of the funnel are the remains of a sub-lake paleo-talik, from which mineralized water and gases were expulsed into the yet unfrozen reservoir that previously existed at this place. The component composition of gases suggests that they are products of biochemical processes similar to those that occur in modern peatlands. The δ13C value for methane extracted from the sediments of the near-contact zone of the Yamal crater was found to be −76%. The predominance of high molecular weight normal alkanes in frozen bitumen indicates that the original organic substrate which was buried contained remains of higher vegetation. The Yamal funnel was formed by the sediment’s “explosion” while the water-gas fluid was released. The volume of the ejected sediment amounted to about 220 thousand m3.