他念他翁山中段第四纪冰川作用ESR定年初步研究

The preliminary study of the Quaternary glacier in middle part of the Tenasserim Chain with ESR dating method

他念他翁山中段地处青藏高原东南部和云贵高原过渡地带,海拔4 200 m以上保存着确切的第四纪冰川遗迹.对其进行深入研究,不仅可以重建横断山脉冰川作用的演化历史,还能够为青藏高原的隆升机制提供重要依据.采用野外地貌调查与电子自旋共振测年(ESR)相结合的方法,查明他念他翁山第四纪冰川发育的地貌特点,并初步对研究区的冰期系列进行划分.结果显示,他念他翁山中段古冰川类型主要为山麓冰川、山谷冰川和冰斗冰川.晚第四纪以来至少经历了4次冰川作用,分别为倒数第二次冰期(MIS 6),年代为(192±51)^(207±45)ka;末次冰期中期(MIS 3),年代为(55±8)^(54±9)ka;末次冰盛期(M IS 2),年代为(25±1)^(38±6)ka,以及全新世新冰期/小冰期(MIS 1).

The Tenasserim Chain is the transitional zone between the southeast of Tibetan Plateau and Yunnan- Guizhou Plateau. Typical glacial erosion and sedimentary landforms of the late Quaternary can be identified in the study area higher than 4 200 m a. s. 1. The glacial sequence with absolute ages not only can reconstruct evolutionary history of the Hengduan Mountain range but also provide critical basis for studying the effect of the uplifting mechanism of the Tibetan Plateau. According to the field investigation and ESR dating results, it is ascer- tained that the basic geomorphology features of the Quaternary glaciers and the glacial sequences in the study area. The results show that the glacial types were cirque glacier, valley glacier and piedmont glacier. There were four glacial advances in the middle Tenasserim Chain at least during the Late Quaternary. These glacial advances can be assigned to the Penultimate glaciation （MIS 6, MIS = Marine Oxygen Isotope Stage） during the Middle Pleistocene E （ 192 ± 51 ） - （ 207 ± 45） ka], the middle stage of the last glacial cycle [ MIS 3, （55 ±8 ） - （54 ± 9） ka], the last glacial maximum IMIS 2, （25 ±1 ） - （38 ±6） ka] during the Last Pleistocene and the neoglaciation/Little Ice Age during the Holocene （MIS 1 ）.