Luminescence chronology of late Quaternary moraines and Last Glacial Maximum equilibrium‐line altitude reconstruction from Parlung Zangbo Valley, south‐eastern Tibetan Plateau

Abstract

ABSTRACTOptically stimulated luminescence dating was applied to samples from glacial sediments in the Parlung Zangbo Valleys (Daba and Charao) of the south‐eastern Tibetan Plateau to better constrain the timing of Late Quaternary glaciation, which is thought to have been linked to the Indian monsoon. The single aliquot regenerative‐dose protocol on quartz was used for equivalent dose (De) determination using small aliquots. For samples from the Daba Valley, the comparison of ages using two grain size fractions, middle (38–63 µm) and coarse (90–250 µm) were conducted. The coarse grain ages in the Daba Valley (P3) and Charao Valley (P7) range from 16.4 to 26.0 ka, and are consistent with previously published cosmogenic radionuclide exposure ages in the Baiyu Valley (PB1). Our dating results reveal that these moraines were formed during the Last Glacial Maximum (LGM). We then reconstruct the past equilibrium‐line altitudes (ELAs) during the LGM for five glacial valleys in the study area, which range from 3286 to 4014 m with an average value of 3730 m, while the contemporary average ELA is 4655 m. After correction for terrain uplift (about 8 m since the LGM), the difference in the ELA values between the LGM and today is 917 m. According to these data, the estimated temperature during the LGM is 6.3 °C lower than present for the Parlung Zangbo River Valley.