Periglacial conditions in the Western Karakoram

Abstract

Article in French.

ORIGINAL TITLE: Le périglaciaire dans le Karakorum de l'Ouest

Exploration was carried out during the 1958 Austrian expedition to the Karakoram, in the Haramosh region (7,400 m above sea level, Saltoro Karakoram) and the Ladakh Karakoram, as well as in the valleys of the Gilgit and Indus rivers. In the periglacial zone of the Karakoram, physical weathering and frost denudation were very intense during the glacial periods. Consequently, many slopes are covered with a thick layer of scree, strongly cemented by solifluction debris. Below the solifluction zone, runoff operated to a much greater extent than today. In the lower levels of the Karakoram, the Pleistocene glacial periods were also pluvial periods. As a result of increased rock weathering, solifluction and surface water runoff caused the valleys to fill with massive sediments, with terraces carved out during interpluvial periods. Three series of Quaternary sediments were identified and correlated with the Würm, Riss and Mindel glaciations. The oldest Pleistocene series reaches a thickness of over 800 metres, and valleys were cut into it to their present depths even before the Mindel series formed. Contemporary periglacial formations appear only above 3,000 meters above sea level. No structural soils were identified but, rather, turfed steps, tuffets and numerous scree tongues sliding down the bottom of the cirques. In all of these formations, the penetration of meltwater into the ground plays a significant role.