太湖全新世沉积物有机联同位素的分布及其古气侯意义

通过太湖两个钻孔岩芯有机碳同位素（１３Ｃ／１２Ｃ）的分析，发现δ１３Ｃ的垂直分布与太湖地区１６０００ａＢ．Ｐ．以来古气候波动相关。根据δ１３Ｃ垂直分布曲线可推测，大约在１１０００—６０００ａＢ．Ｐ，太湖地区处于温暖湿润期，气温高于现在平均温度。另一方面，根据太湖两岩芯沉积物的δ１３Ｃ值的对比发现，大约在１１０００—６０００ａＢ．Ｐ，西太湖（Ｗ１Ｂ）岩芯沉积物的δ１３Ｃ平均值明显高于东太湖（Ｅ２Ｂ）。据此可认为，在这一期间西太湖很可能有过海水侵入。

DISTRIBUTION OF ORGANIC CARBON ISOTOPESIN RECENT SEDIMENT FROM TAIHU LAKEAND THEIR PALEOCLIMATIC IMPLICATIONS

Two sediment cores (W,B and E,B) from Taihu Lake were analyzed for their deltacarbon isotopes("C/"C).W,B was collected from West Taihu Lake, while E,B was fromEast Taihu Lake. Of fifteen samples determined for East Taihu Lake, the average valuefrom Z17cm (e. g. 16 000 aB.P.)is-22.76, the average value between depths of200-90 cm (e.g.,6 500-6 000 aB. P. )is-27.07 and the average value from 90cmsurface (e.g.6 000 aB. P.to present) is-22. 87. As for the fifteen samples determinedfor West Taihu Lake, the average value between depths of 280 and 70 cm (e. g. 11 0006 000 aB. P.)is-23.94,and from 70cm-surface(e.g.,6 000 aB.P.to present)is~23.55.Comparing the a 13C values before and after 6 000 aB. P. between West Taihu Lakeand East Taihu Lake,we found that the values are lower in the period before 6 000 aB. P.as compared to the years after 6 000 aB.P.The lower values correspond to the higher average regional temperatures, while the higher values correlated to the lower average regional temperatures. When comparing the 8 13C values between West Taihu Lake and EastTaihu Lake,we found that the 6 13C values from West Taihu Lake are much higher thanthe values obtained from East Taihu Lake. This difference may be attributed to the organic carbon sources.The low 8 13C values obtained from East Taihu Lake prior to 6 000 aB.P.could be due to the heterotrophic carbon source from the watershed.This is likely toreflect running water environments such as rivers or streams,while the much higher 8 13Cvalues from West Taihu Lake are likely to indicate autotrophic carbon sources, reflecting alacustrine environment.This also shows that the western part of Taihu Lake was in a lacustrine environment about 11 000 aB.P.,earlier than East Taihu Lake. East Taihu Lakeprior to 6 000 aB.P.has been shown to have been a running water environment with asubstantial proportion of organic carbon input from the watershed.It became a lacustrineenvironment after 6 000 aB.P.