ESR Dating on Tills and the Last Glaciation at the Headwaters of the rmqi River, Tianshan Mountains, China

Using Ge center of quartz grains of size 0.06～0.25 mm, ESR (electron spinning resonance) dating on the glacial quartz sands formed in the Last Glaciation was made at the headwaters of the rumqi River in the Tianshan Mountains, Northwest China. ESR dating on a basal till (subglacial melt-out one) of an end moraine formed in the late stage of the Last Glaciation is consistent with the dating under AMS 14 C method. But dating on the overlying till (supra glacial melt out one) of the same moraine is different from the dating under AMS 14 C method. The underlying till contains much more silt than the overlying till. High content of silt implies a strong subglacial comminution. Based on an experiment, Ge signal in quartz grains decreases by one third after artificial grinding for ten minutes.The till was formed in 50～70 ka BP, the early stage of the Last Glaciation. It was spread in the main valley as low as 2300 m a.s.l. with a length of more than 19 km. Fluvial sandy gravel deposited in the inter glaciation between the early and late stages of the Last Glaciation.