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中国古气候研究的重要内容之一,就是要研究中国季风形成的机制和演化过程。中国南方岩溶区地处夏季风最敏感的地区,但由于缺乏象湖泊、冰芯和黄土那样的记录载体,还缺乏高分辨率古气候研究成果。因此,通过对桂林盘龙洞一1.22m长,直径约45 cm石笋的加速质谱~(14)C测年和详细的氧碳同位素记录以及洞穴环境的研究,初步得出以下结果:①由末次冰期向全新世的突然变暖过程中,有一短暂冷事件记录,发生时间大约在距今11.3～10.8 ka,这可能是新仙女木事件在该地区的反映;②在距今9.0～7.0ka,该地区逐渐变得温暖和湿润,即夏季风逐渐增强,但在其期间同位素记录也显示存在一些小波动,即在距今9.0～8.0ka,夏季风较强,而在距今8.0ka左右,δ~(18)O值增加,可能记录了一次短暂的冷事件;③从距今7.0～4.5 ka,尤其距今6.0～4.5 ka,δ~(18)O总体上比现代碳酸盐的δ~(18)O值低,同时石笋的生长速度最大,δ~(13)O值也低,因此这一时期可能夏季风要比现代强,但在距今5700年至距今5500年,δ~(18)O值与现代相似,表明夏季风有所减弱;④在距今4.5 ka后,δ~(18)O值与现代δ~(18)O值相似,这表明夏季风减弱,该地区进入现代气候模式,石笋的生长速度减小,在距今几百年前停止生长。但在近几千年中,也有数次波动,即在距今4.0～2.5 ka,距
One of the important contents of ancient Chinese climate research is to study the mechanism and evolution of the monsoon formation in China. The southern karst region is located in the most sensitive part of the summer monsoon but lacks the high-resolution paleoclimate research due to the lack of record carriers such as lakes, ice cores and loess. Therefore, the accelerated mass spectrometry ~ (14) C dating and detailed oxygen-carbon isotope records and cave environment studies of Panlongdong-1.22m long stalagmite and about 45cm diameter stalagmite in Guilin have been carried out. The results are as follows: (1) From the last glacial period In the process of sudden warming to the Holocene, there was a record of a brief cold event occurring about 11.3 ~ 10.8 ka from now on, which may be a reflection of the new fairy wood event in the area. ② In the period from 9.0 to 7.0 ka, The area gradually became warmer and humid, ie, the monsoon gradually increased. However, the isotopic records during this period also showed some small fluctuations, that is, from 9.0 to 8.0 ka, the summer monsoon was stronger than before and 8.0 ka (18) O values may have recorded a brief cold event; (3) δ ~ (18) O is generally larger than δ ~ (18) O of modern carbonate from 7.0 to 4.5 ka, especially from 6.0 to 4.5 ka (18) The value of O is low, and the growth rate of stalagmite is the highest and the value of δ ~ (13) O is also low. Therefore, the summer monsoon may be stronger than the modern one in this period, but from 5700 years ago to 5500 years ago, (18) The O value is similar to the modern one, indicating that the summer monsoon is weakened. ④ After 4.5 ka, the δ ~ (18) O value is similar to the δ 18 O value, indicating that the summer monsoon The region into the modern climate models, stalagmite growth rate decreases, stop growing dating back hundreds of years ago. However, in recent millennia, there have been several fluctuations, that is, 4.0 ~ 2.5 ka away from now