The Western End of the Tibetan Plateau

Abstract

The Tibetan plateau terminates between the NW-SE oriented, right-lateral strike slip Karakorum fault and the E-W oriented, left-lateral strike slip Altyn-Tagh fault, forming a wedge from wich Tibet is now being extruded eastwards.

The Plio-Pleistocene Sutlej basin, the Garpo pull-apart, the Purang and the Shiquanhe grabens are associated with the late Tertiary displacement of the Karakorum fault system.

In this western part of the plateau, the S (Lhasa) and N (Qangtang) Tibetan Blocks can be subdivided into four zones (fig. 1):

• 1- The Ladakh — Kailas zone is bounded to the S by the Indus —Yarlung suture and to the N by the Shiquanhe ophiolitic melange.The latter can be followed along the Karakorum fault, dismembered, and correlated westward with the Shyok melange (fig. 2).

• 2- The South-East trending Bancong Lake zone consists mainly of early to middle Cretaceous sediments intruded by huge (?)late Cretaceous granitic bodies. This zone can be correlated with the Saltoro belt appearing W of the Karakoram fault, between the Shyok and Nubra valleys (fig. 2).

• 3- The East Changchemno zone belong to the Qangtang Block, bounded to the S by the late Jurassic Bancong — Nujiang suture and is separated from the Loqzung zone to the N by the SW-NE oriented, left-lateral strike slip Changchemno fault. We correlate the Bancong -Nujiang suture with the N Saltoro suture in Ladakh and the Northern suture in Pakistan. To the NW, the East Changchemno zone can be followed into the Aghil — Shaksgam sedimentary belt of the Karakorum Tethys.

• 4- The Loqzung zone consists of a curved NW to E trending belt of folded late Paleozoic to late Cretaceous mainly shallow water sediments.