收稿日期: 1994-11-03
修回日期: 1995-03-20
网络出版日期: 1995-12-01
基金资助
瑞士国家基金和中国国家自然科学基金项目(编号:4880140;49070159;49291100)资助.
ADVANCE IN 10Be STUDY IN CHINESE LOESS
Received date: 1994-11-03
Revised date: 1995-03-20
Online published: 1995-12-01
80年代中期，中国和瑞士科技工作者开始联合进行黄土10Be研究。建立了黄土10Be AMS测量的理想流程，发现了10Be在黄土地层良好保存性等重要地球化学行为特征，确认了黄土10Be研究具有重要意义。对洛川黄土剖面0.4～138m段600多个样品进行了10Be测定，建立了2.5Ma以来大陆堆积物同位素记录曲线。地磁极性倒转期间，10Be浓度平均增高20～25％、持续20～30ka。洛川、西峰黄土剖面10Be变化与深海沉积物δ18O变化之间均存在极好相关性，据此建立了75万年以来黄土地层相对10Be时标；黄土堆积速率与各时期10Be沉降通量之间亦存在良好的线性相关关系，据此可望建立10Be绝对时标。探讨了Raisbeck峰事件、10Be/26Al比值等在黄土地层定年中的应用前景和途径。引入物理意义明确的“磁性物质通量”概念，建立了10Be—磁化率模型，定量估算出磁化率中降尘和成壤两组分相对贡献，求得洛川区域S0、L1、S1三时期年均降水量。精确测定了黄土石英中“就地”成因10Be含量，获得不同时期黄土源区侵性速率。
沈承德,易惟熙,刘东生 . 中国黄土10Be研究进展[J]. 地球科学进展, 1995 , 10(6) : 590 -596 . DOI: 10.11867/j.issn.1001-8166.1995.06.0590
In the middle of 1980’s, an effective procedure for 10Be measurement in loess by AMS has been established. Some important geochemistry behaviors such as good preservation of 10Be in loess strata have been observed, showing obviously that the investigation on 10Be in loess would be very significant. A total of more than 600 samples from the upper 0.4~138m of the Luochuan section was analysed for 10Be concentrations and an isotopie curve of continental deposition since 2.5Ma has been established. Relative increase of 20~25% of 10Be concentration within 20~30ka duration are observed in the vicinity of the geomagnetic reversals. The linearity of relationship between accumulation rate and 10Be flux of loess is also astonishingly good. It reveals a new way for the dating of loess strata. Both the event of Raisbeck peak at 35000 a BP and 10Be/26Al ratio have been studied, which are expected to be new dating methods for loess strata. Based on 10Be-susecptibility model with a new concept of magnetic material flux, pedogenic ferromagnetic material flux in Chinese loess have been estimated quantitatively and average paleorainfall values in Luochuan region have been calculated. The concentrations of in situ cosmogenic 10Be in quartz from loess have been measured accurately and the erosion rates of the source regions have also been calculated.
Key words： Loess; 10Be syudy.
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