玉龙雪山冰川沉积序列OSL定年

OSL dating of the Quaternary glacial sedimentary sequences at Mt.Yulong,China

位于青藏高原东南缘的玉龙雪山分布有欧亚大陆纬度最低的海洋型冰川,其主峰及周边地区保存了大量清晰完整的第四纪冰川遗迹.研究该区第四纪冰川作用遗迹及其冰川作用史,具有重要的理论与实际价值.应用光释光(OSL)测年技术对玉龙雪山冰川沉积物进行了定年,结合前人研究资料,重建玉龙雪山冰川作用史.研究结果表明:玉龙雪山东麓的末次冰期冰碛物主要形成于晚更新世末次冰期最盛时期,其平均年代约在25 ka,西麓末次冰期冰碛物形成年代约为50 ka,对应于深海氧同位素3阶段中期(MIS 3b).而倒数第二次冰期的年代在240 ka左右,处于中更新世晚期,对应于MIS 8阶段,当时玉龙雪山存在多条复式山谷冰川.该研究可为玉龙雪山第四纪冰川作用历史的重新认识以及光释光测年技术在该区的应用提供基础资料.

The Mt. Yulong is situated in the southeast of the Tibetan Plateau, where the well preserved glacial remnants （including the lowest latitude moraines in the northern hemisphere） provide a natural laboratory to study the Quaternary glacial and the past global climate evolution process. Getting more details about these glacial remnants is important for deeply understanding the regional change of paleo-climate and paleo-environment, as well as the development and utilization of the glacial tills. However, because of shortage of dating records and controversy of climate background, there are no consensus about how many times of glacier advance during the Quaternary. In this paper, OSL dating techniques was used on the glacial sediments at Mt. Yulong. OSL dating data and evidences from geomorphology and stratigraphy reveal that glaciers had advanced during local last glacial maximum （~25 ka） at east side and mid-MIS 3b （~50 ka） at west side of the Mt. Yulong. The Penultimate Glaciation had appeared at ~240 ka in late Middle Pleistocene, corresponding to MIS 8. At that time, there were multiple composite valley glaciers at Mt. Yulong.