中国第四纪冰期划分改进建议

由刘东生主持1位研究者提出的"以气候变化为标志的中国第四纪地层对比表"一文发表已近2a,其中由施雅风执笔第四纪冰期与海洋同位素对比部分.由于新情况的出现,需作适当改进:1)周尚哲等应用ESR测年确定祁连山北坡摆浪河源中梁赣海拔299m,高出现代河床500m处冰碛年代为42.9ka BP,天山乌鲁木齐河上游高出河床200～300m的高望峰阶地冰碛样品ESR测年为477.1ka BP和459.7ka BP,均相当于MIS 12阶段,该阶段国际上对应Kansan-Mindel冰期,与MIS 2、MIS和MIS 1都是100ka周期δ¹⁸O值特低时期;2)古里雅冰芯记录中相当于MIS3b阶段,δ¹⁸O值折算温度比现代低5℃左右,已经发现台湾雪山山庄期冰碛TL年代为(44.25±3.72)ka BP,天山乌鲁木齐河谷一处冰碛ESR年代45.9ka BP,喜马拉雅山、喀喇昆仑山和兴都库什南坡测定对应此时段冰川前进更为显著,初步检查亚、欧、北美、南美和澳洲12个地区23个地点相应于MIS 3b冷期冰川前进规模均超过MIS 2阶段,即常说LGM时,推测MIS 3b的降温值虽不及MIS 2,但降水较多,有利于冰川发展;3)MIS 3a暖期,不仅青藏高原异常暖湿,而且中国全境的降水量普遍高于现代,并有较大范围的海侵与仅低于现代海面8～10m的高海面,气候环境实际达到间冰期程度.上述3点应补充入中国冰期划分表.

A Suggestion to Improve the Chronology of Quaternary Glaciations in China

Table of Chinese Quaternary Stratigraphic Correlation Remarked with Climate Change presented by 16 authors under the direction of CAS Academician Liu Dongsheng has been published for nearly two years, of which a part, entitled by Comparative Study on the Quaternary Glaciations and Maritime Isotope, was written by Shi Yafeng. In view of recent discovery, the following three points are suggested to supplement the Chronology of Quaternary Glaciations in China. (1) ESR dating demonstrates that the age of the moraine at 2996 m a.s.l., 500 m above the present river bed, in the Zhonglianggan Mountain in the headwaters of the Bailang River on the north slope of the Qilian Mountains was 462.9 ka BP, and those of the moraines at Gaowanfeng terrace, 200～300 m above the present river bed, in the upper reaches of the Urumqi River in the Tianshan Mountains were 477.1 ka and 459.7 ka BP. These are equivalent to MIS 12, which may correspond to traditional Kansan-Mindel glacial period. The period, together with MIS 2, MIS 6 and MIS 16, belongs to the major sequence with 100 ka cycle. (2) Temperature in MIS 3b, calculated from the δ¹⁸O recorded in Guliya ice core, was about 5℃ lower than that at present. Moraine of shan Zhuang stage in Xueshan Villa in Taiwan has a TL Age of (44.25±3.72) ka BP, and moraine in the Ürümqi River valley at the high wang feng stage of the Tianshan Mountains has an ESR Age of 45.9 ka BP. Corresponding to this stage, the advance of glaciers in the Himalayas, the Karakorum Mountains and the southern slopes of the Hindu Kash Mountains was more evident. According to a preliminary study, in the cold MIS 3b, glaciers in 23 sites of 12 regions in Asia, Europe, North America, South America and Australia all advanced in a scale even greater than that in MIS 2. In other words, during the LGM, in MIS 3b precipitation was plenty and favourable to the extension of glaciers, although the inferred temperature reduction was less than that in MIS 2. (3) During the warm MIS 3a, not only the Tibetan Plateau had an unusual warm and humid climate, but also the whole China had rich precipitation, more than that at present in general, together with large area of transgression, with a high sea level, merely 8～10 m lower than that at present. Climate and environment in MIS 3a was virtually comparable with the interglacial period.