摘要
Toba火山活动是第四纪最大的火山事件,其中最年轻的约0.074 Ma的火山活动被称为YTT事件(TheYoungest Toba Tuff)。已有的研究表明,YTT事件对第四纪的环境气候变化具有重要的影响,黄土S1/L1界面处的磁化率和粒度等因子突变所反映的夏季风迅速回撤可能响应了这一事件。对洛川黄土S1/L1界面处的固定铵和速效钾进行了研究,结果表明,YTT在洛川黄土S1/L1界面处有很清楚的记录,具体表现为固定铵和速效钾的特殊异常。固定铵的异常主要记录了YTT事件所产生的酸雨沉降,速效钾的异常则是由于YTT微细火山灰尘在黄土剖面及其广阔的物源区伴随酸雨沉降的结果,厚达1 m的异常带表明末次冰期冬季风逐渐强盛和南移的过程。
The Youngest Toba Tuff （YTT） eruption was the greatest single volcanic event which occuned in the Quaternary, dated back to 74 ± 2 ka., and bad important impacts on global environmental and climatic changes. Previous investigations showed that proxies such as magnetic susceptibility and particle size changed suddenly across the contact of S1/L1 in the Luochuan loess, which was considered to be in response to this volcanic event. In this study, significant anomalies of available potassium （K） and fixed NH4^＋ were found in the contact of SI/LI in the Luochuan loess. Abrupt changes in available K resulted from the falling of fine tephra of the YTT eruption, and its abnormal zone about 1 meter thick implied that the fine tephra of the YTT eruption falling in wide provenances of loess was secondly carried with eolian dust into the loess Plateau of China by the East Asian winter monsoon during the early stage of the last glacial period. Fixed NH4^＋ changed suddenly with a high value of 240 × 10^-6 in the contact of S1/L1, indicating that acid rain containing sulfate aerosols induced by the YTT event was precipitated on the Loess Plateau of China. Therefore, these lines of evidence demonstrated clear records of the YTT event preserved in the Luochuan loess.
出处
《矿物学报》
CAS
CSCD
北大核心
2007年第3期325-329,共5页
Acta Mineralogica Sinica
基金
国家自然科学基金(批准号:4990202440672053)
关键词
固定铵
速效钾
YTT事件
洛川黄土
fixed NH4^＋
available potassium （K）
Luochuan loess
YTT event
