Home – Home – Jornals – Earth’s Cryosphere 2021 number 6

The purpose of the article is to reveal the conditions of occurrence and formation of subpermafrost waters, which have been exposed by wells in the Paleozoic, Triassic terrigenous rocks and the Lower Cretaceous granitoids of the Chukotka Upland. In the Paleozoic strata, the confined subpermafrost waters were exposed at depths from 223 to 340 m. The specific yield of wells varies from 0.01 to 0.5 L/(s·m), the composition is predominantly chloride, mineralization ranges from 0.2 to 1.3 g/dm³. In the Triassic rocks at depths from 100 to 300 m, the piezometric surface of waters is higher than the wellhead levels by 3-4 m and up to 58.4 m. The specific yield of wells varies from 0.00001 to 0.25 L/(s·m). The waters are chloride, hydrocarbonate and sulphate, salinity ranges from 0.1 to 3.1 g/dm³. In granitoid massifs, the thickness of permafrost near the sea coast is about 100 m; on the watersheds, it is about 450 m. The specific yield of wells varies from 0.0001 to 0.013 L/(s·m). The obtained data, confirmed by the magnetotelluric sounding, indicate the development of hydrogeological massifs composed of igneous and metamorphosed rocks in the upland. Structures with quasi-stratum fracture reservoirs, associated with overthrusts and faults, were formed in the terrigenous Triassic strata. The impermeable fault planes divide the quasi-strata into sections, which are poorly interconnected hydraulically. For this reason, in the Triassic subpermafrost strata, the stagnant or extremely impeded water exchange predominates persisting for more than 400 thousand years; in the hydrogeological massifs, the water exchange is more active.