摘要
Dating lake sediment using sedimentary event is the supplement and calibration to traditional dating by radionuclide such as 210Pb and 137Cs. Based on the change of spheroidal carbonaceous particle (SCP) concentration, the age sequence of lake sediments can be deduced. It is one of the dating methods using sedimentary event. SCP is formed from combustion of fossil fuel at high temperature up to 1750℃ and at a rate of heating of approaching 104 ℃/s. It can be dispersed to several hundred kilometers away from its source and deposited with precipitation or dryly deposited, and kept in sediments. Compared with Cs or Pb, there is no evidence for SCP that it decays in lake sediments and is un-removable once stored except by physical disturbance because it is mainly composed of element carbon. Handy method to extract, identify and calculate has been developed. Although fossil fuel has been used early in China, combus- tion at high temperature started later since emergence of electricity generation. The productivity of SCP is positively related with the generated thermal power, which is reflected as the SCP concentration in lake sediments increases with the increase of generated thermal power. Therefore, reliable sediment markers from the start of the SCP record and the remarkable variation can be used for dating purpose. In China, electricity industry started from the 1950s, and rapid increase of generated power took place since 1978. Based on these time markers, SCP time sequences of lake sediment cores LH and LL-4 from Longgan Lake, the middle reach of the Yangtze River, have been established, which is compara- ble with the results from 137Cs and 210Pb, and has eliminated the errors of dating using 137Cs and 210Pb.
Dating lake sediment using sedimentary event is the supplement andcalibration to traditional dating by radionuclide such as ^(210)Pb and ^(137)Cs. Based on the changeof spheroidal carbonaceous particle (SCP) concentration, the age sequence of lake sediments can bededuced. It is one of the dating methods using sedimentary event. SCP is formed from combustion offossil fuel at high temperature up to 1750 deg C and at a rate of heating of approaching 1ft4 °C/s.It can be dispersed to several hundred kilometers away from its source and deposited withprecipitation or dryly deposited, and kept in sediments. Compared with Cs or Pb, there is noevidence for SCP that it decays in lake sediments and is un-removable once stored except by physicaldisturbance because it is mainly composed of element carbon. Handy method to extract, identify andcalculate has been developed. Although fossil fuel has been used early in China, combustion at hightemperature started later since emergence of electricity generation. The productivity of SCP ispositively related with the generated thermal power, which is reflected as the SCP concentration inlake sediments increases with the increase of generated thermal power. Therefore, reliable sedimentmarkers from the start of the SCP record and the remarkable variation can be used for datingpurpose. In China, electricity industry started from the 1950s, and rapid increase of generatedpower took place since 1978. Based on these time markers, SCP time sequences of lake sediment coresLH and LL-4 from Longgan Lake, the middle reach of the Yangtze River, have been established, whichis comparable with the results from ^(137)Cs and ^(210)Pb, and has eliminated the errors of datingusing ^(137)Cs and ^(210)Pb.
基金
This work was supported by the National Natural Science Foundation of China(Grant No.40302022)
“973”project(Grant No.2002CB412303)
the Knowledge Innova-tion Project of the Chinese Academy of Sciences(CAS)(Grant No.KZCXI-SW-l2).
关键词
湖泊
沉淀物
年代测定
地质研究
spheroidal carbonaceous particle
time marker
time sequence
lake sediments
Longgan Lake
