Sequences of the Quaternary Glacial Sediments and Their Preparatory Chronology in the Tomur River Valley,Tianshan Mountains

The Tomur River originates on the southwestern slopes of the Tomur Peak,the largest modern glaciation centre in the whole Tianshan Mountains.Five sets of moraines are well-preserved in this valley during the Glacial-interglacial cycles in Quaternary,recording a complex history of Quaternary glacial landscape evolution.ESR dating technique was applied to determine the first and the second glacial terraces(The tills distribute from the Tomur Bridge to the confluence of the Guwar River and the Tomur River) and the oldest glaciated plateau of this valley.The ages of the first and the second glacial terraces and the glacial plateau are 18.7~20.1 ka BP,20.8 ka BP and 418.9 ka BP,respectively.Considering the principles of geomorphology and stratigraphy and these preliminary dating results,the following conclusions could be drawn: the tills deposited in Little Ice Age,Neoglaciation,Last Glaciation,MIS 6 and MIS 12,respectively.The glacial landforms indicate the ancient glacier was about 47 km,60 km,≥70 km in length at their maximum extent in Neoglaciation,Last glaciation and MIS 6.The age of the oldest glaciated plateau demonstrates that at least this segment of Tianshan Mountains began to develop glacier in MIS 12.