TERRESTRIAL AND OFFSHORE PERMAFROST EVOLUTION OF THE LAPTEV SEA REGION DURING THE LAST PLEISTOCENE-HOLOCENE GLACIAL-EUSTATIC CYCLE

摘要

The terrestrial permafrost of the Laptev Sea Region (LSR) is continuous and between 500-800 m thick. The mean annual ground temperature (t_(ma)) decreases northward from -5°C to the south of the coastal lowlands to -15°C north of Kotelny'i island. An important component of the upper permafrost is the 40-50 m thick "ice complex". It is a basement for thermokarst lake and alas formation. Offshore ice-bonded permafrost (IBRP) is relic, continuous to isobate -65 m, and discontinuous from there until isobate 100-120m. The thickness of IBRP decreases at equal sea depth northward and is greater on tectonic depressions than on uplifts. With its maximum thickness north of Kotelny island (450-530 m), the IBRP layer thickness decreases with increasing sea water depth to about 80-50 m between isibath -100-120 m. A map of IBRP thickness has been compiled for eastern part of Laptev Sea Shelf.