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石笋凭借其准确的年代学和对洞穴外界环境的敏感响应,已经成为第四纪研究的重要力量。亚洲季风区轨道-千年尺度石笋δ18O指示亚洲季风强弱的变化,但是在更短的时间尺度上,石笋δ18O则可能受到其他因素的影响,因此近现代、能与器测记录进行对比的石笋记录研究是衔接现代气候与古气候的关键环节。而这关键环节中的关键问题就是确定石笋的沉积年代。寻找一种适合于无生长纹层、低U含量石笋样品的年代方法对于解决石笋沉积年代有着重要的推动作用。本研究选择广西桂林茅茅头大岩一正在生长的年轻石笋。由于低U含量、高232 Th含量,U系-230 Th定年不成功。利用210Pb定年计算出平均沉积速率为1.96±0.23mm/a,但由于多层晶间孔隙的存在,计算结果偏小。由于石笋中14 C基本为核爆产生,AMS 14 C测试结果计算石笋平均沉积速率为2.10mm/a,但由于未测量到核爆前14 C数据,其值可能仍偏小。由于前人研究指出桂林地区石笋记录能记录夏季风降水,结合桂林多年降水数据,综合计算出该石笋平均沉积速率为2.44mm/a,生长时限为2009—1968年。平均沉积速率和沉积时代的确定,为后续的石笋现代气候研究,进而与古气候衔接提供了重要的研究基础。
Stalagmites, with their accurate chronology and their sensitive response to the external environment of caves, have become an important force in Quaternary research. Asian monsoon orbit - the millennial stalagmite δ18O indicates changes in the strength of the Asian monsoon, but on a shorter time scale, stalagmite δ18O may be affected by other factors, so modern, stalagmite records can be compared with the measured records Research is a key link between modern climate and paleoclimate. The key issue in this crucial aspect is to determine the depositional age of stalagmites. Looking for a non-growth pattern layer, low U content stalagmite samples age method for solving the deposition of stalagmite has played an important role in promoting. In this study, a growing young stalagmite was selected from the rock of Gui Mao Tou, Guilin, Guangxi. Due to the low U content, high 232 Th content, U-230 Th dating was unsuccessful. The average deposition rate calculated by 210Pb dating is 1.96 ± 0.23mm / a, but the calculation result is small due to the existence of multi-layer intergranular pores. Since 14 C is basically a nuclear explosion in stalagmite, the average deposition rate of stalagmite calculated by AMS 14 C is 2.10 mm / a. However, the value of 14 C before nuclear explosion may be still small. As previous studies indicate that stalagmite records in Guilin can record summer monsoon rainfall, combined with years of precipitation data in Guilin, the average deposition rate of stalagmite was calculated to be 2.44 mm / a, with a growth period of 2009-1968. The determination of average sedimentation rate and depositional age provides important research foundation for the follow-up study of modern climate of stalagmite and its connection with paleoclimate.