自然资源部岩岩溶动力学重点实验室

公元8世纪以来贵州荔波石笋高分辨率的气候变化记录

2008-09-28KDL 2649

High resolution stalagmite records of climate change since 800a A. D. in Libo, Guizhou
[Abstract] Stalagmite L1 and stalagmite L2 f rom Longquan cave (N 25°29′, E107°52′, 550m altitude) at Libo,Guizhou are 50cm and 192cm high respectively. On the basis of 19 ICP-MS 230Th ages and 459 stable oxygen-carbon isotope samples analysis, it proves that the stalagmite L1’s time range is from 918a A. D. to1910a A.D. and the stalagmite L2 is from 724a A. D. to 1888a A. D. . The stable isotope average resolution of the stalagmite L1 and stalagmite L2 are 6. 6a and 3. 6a respectively. The records of δ18O from the two stalagmite are coherent, which can be divided into three climatic periods: (1) Medieval cold period (724- 995 a A.D. ).During this period, δ18O of the stalagmite becomes heavier but the change scope is small, and the ligh testvalue of oxygen isotope is - 8. 84‰ , the heaviest value is - 6. 72‰ and the average is - 7. 76‰ which is 0. 16‰ heavier than the average value of the two stalagmite (- 7. 92‰) ; (2)Medieval warm period (995-1340 a A. D. ). It is recorded by stable oxygen isotope in the shape of two wave crest and one trough which form half a 2002 year gyration, corresponding to two strong monsoon periods and one relative weak monsoon period. And the lightest value of oxygen stable isotope is - 9. 47‰, the heaviest - 6. 58‰ and the average - 7. 94‰; (3) Small ice age (1340- 1880 a A. D. ). This climatic period is recorded by stalagmite in the form of three wave crests and four trough salternately that indicates 3 and half a 2002 year monsoon gyration. Inth is climatic period, the lightest value of stable oxygen isotope is - 9. 50‰, the heaviest - 6. 07‰ and the average - 7. 92‰ which is larger than that of the medieval warm period and furthermore, fluctuating range of stable oxygen isotope is bigger than that of medieval warm period, especially in weak monsoon period. The stable oxygen isotope records from stalagmite L1 and stalagmite L2 parallels phonological records in east China well. As a whole, the change pattern of stalagmites can parallel records in the Greenland ice core. The stalagmite records can also parallel the production of cosmic nuclide and solar flare records. During smallice age, four troughs of stable oxygen isotope in stalagmite records (weak monsoon period) just correspond to low productive rate of cosmic nuclide and troughs of solar flare curve, and furthermore, four t rough of stalagmite records coincided with sunspot activit ies: Dalton Minimum (1810) , Maunder Minimum (1645-1715) , Spreal Minimum ( (1420-1530) and Wolf Minimum (1280-1440) respectively. The change of sunspot leads to the change of solar radiant energy received by the earth directly. It shows that short scale monsoon climate at low latitude zone immediately respond to change of solar radiant energy.
[Key words]  oxygen isotope of stalagmite; age dating of ICP-MS 230Th; paleoclimate record; Longquan cave in Libo , Guizhou
[摘 要]  通过中国贵州荔波龙泉洞L 1 及L 2 两根石笋19 件ICP-MS230Th 测年和459件氧稳定同位素分析, L 1 时限范围为918- 1910aA. D. ,L 2 为724- 1888aA. D. ;稳定同位素样品的平均分辨率分别为6. 6a 和3. 6a。两根石笋δ18O 记录取得了平行一致的结果, 石笋记录可分为3 个气候期, 即: 中世纪冷期(公元8 世纪- 995aA.D. ) , 石笋δ18O 总的偏重, 变化幅度较小, 最轻为- 8. 84‰, 最重为- 6. 72‰, 平均值为- 7. 76‰; 中世纪暖期(995- 1340aA. D. ) , 石笋记录为两峰夹一谷, 200 年级的一个半旋回, δ18O 最轻为- 9. 47‰, 最重为- 6. 58‰, 平均值为- 7. 94‰; 小冰期(1340- 1880aA. D. ) , 石笋记录为四谷三峰相间交替, 即季风表现出由弱到强的200 年级3 个半旋回, δ18O 最轻为- 9. 50‰, 最重为- 6. 07‰, 平均值与中世纪暖期基本一致, 为- 7. 92‰, 但变化幅度要大一些, 特别是弱季风期要偏重一些。L 1及L 2 两石笋δ18O 记录可以很好地和中国中东部物候记录对比。在总体变化格局上也可以和格陵兰冰芯记录进行对比。石笋记录也可以与宇宙核素产率及太阳耀斑记录进行对比, 小冰期中石笋δ18O 记录的4 个低谷期(弱季风期) , 正好与宇宙核素产率及太阳耀斑曲线的低谷区相对应, 并分别可以和太阳黑子1810 年达尔顿极小值、1645- 1715 年蒙德极小值、1420- 1530 年的斯波瑞尔极小值、280- 440年的沃尔夫极小值一一对应。太阳黑子的变化, 直接改变地球接受太阳辐射能量的变化, 说明低纬度地区短尺度季风气候直接响应于太阳辐射能量的变化。
[关键词] 石笋氧同位素; ICPMS-230Th 定年; 古气候记录; 贵州荔波龙泉洞

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