ESR dating of the sediments of the Last Glaciation at the source area of the Urumqi River, Tian Shan Mountains, China

Abstract

Electron spin resonance (ESR) dates were obtained from glacial quartz sands formed during the Last Glaciation at the source area of the Urumqi River, Tian Shan Mountains, northwestern China. ESR dating of a basal till, interpreted as a subglacial melt-out till deposited in an end moraine which was produced in the late stage of the Last Glaciation, is consistent with ages determined through the AMS 14C method. However, dating of the overlying sediment, interpreted as supraglacial melt-out till associated with the same moraine, produced a result that differs from that determined using the AMS 14C method. Subglacial comminution could reset the ESR signal, thus making ESR dating of basal till possible. The Lower Wangfeng Group, formerly of controversial age, was formed ca. 50–70 ka, during the early stage of the Last Glaciation. It was deposited throughout the main valley as low as 2300 m a.s.l., over a length in excess of 19 km. Fluvial sandy gravel was deposited in the interstadial between the early and late stages of the Last Glaciation.