摘要:
以采自重庆南川地区金佛山羊口洞中一支石笋YK719为研究对象,利用精确的230Th测年数据、δ18O 数据和灰度数据重建了重庆地区早全新世古气候变化序列.将石笋YK719灰度序列和δ18O记录进行对比后发现,在弱季风时段,石笋δ18O值偏重,石笋灰度值较高,灰度序列表现出“谷”构造;反之亦然.分析显示羊口洞石笋灰度序列与树轮△14C数据、太阳黑子数据具有较高的相关性,说明太阳活动是驱动石笋灰度序列变化的一个重要因素.太阳活动可能通过温度和季风降水两方面来影响石笋灰度的变化:温度升高促使土壤微生物活动量增加,土壤中可溶性有机碳和CO2含量增加,从而形成较为纯净的方解石沉积物,石笋颜色暗而透明,反之,石笋表现为不透明乳白色;北大西洋浮冰变化在早全新世可能通过季风—欧亚大陆雪盖耦合来间接地影响亚洲季风降水变化,从而影响石笋灰度的变化.
关键词:
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石笋
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灰度
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全新世早期
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东亚季风
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太阳活动
Abstract:
One stalagmite (YK719) from the Yangkou cave at the Jinfo Mountains,Nanchuan in Chongqing is used as the research object in this article.The purpose is to reconstruct the climate change in the early Holocene with accurate-230 Th dating results,δ18O and grey scale data.Comparison of the grey scale sequence and δ18O suggests that δ18O value was heavier during the weak monsoon period.Accordingly,the grey scale sequence shows a "trough-shaped" pattern.However,it showed "a crest" pattern when the monsoon was powerful.Furthermore,the grey scale value has a good correlation with the tree ring △14C data and the sunspot number,suggesting the solar activity is an important factor in controlling the variation of grey scale values.Solar activity might affect the grey scale value variation via temperature and monsoon precipitation,(1)The increase of temperature leads to the rise of soil microbial activity and a large amount of decomposed or ganic matter.Meanwhile,rock would be dissolved faster for the rise in the dissolved organic carbon and soil CO2.Thus,the relatively pure calcite would be deposited with darkish and transparent appearance.Otherwise,it would be opaque and milky;(2) Solar activity-induced changes in the North Atlantic floating ice may indirectly affect the Asian monsoon precipitation variation through the coupling of the monsoon and Eurasian snow cap in the early Holocene,so as to affect the change of grey scale values of stalagmites.
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