No part of Manchuria was glaciated during the Quaternary, but the surface geology of most of the lower-lying and more fertile parts of Manchuria consists of very deep layers of loess, which have been formed by wind-borne movement of dust and till particles formed in glaciated parts of the Himalayas, Kunlun Shan and Tien Shan, as well as the Gobi and Taklamakan Deserts.[34] Soils are mostly fertile mollisols and fluvents except in the more mountainous parts where they are poorly developed orthents, as well as in the extreme north where permafrost occurs and orthels dominate.[35]