Disentangling Geomagnetic and Precipitation Signals in an 80-kyr Chinese Loess Record of 10Be
Disentangling Geomagnetic and Precipitation Signals in an 80-kyr Chinese Loess Record of 10Be
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DOI：
10.1017/s0033822200041977
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发表时间：
2007
期刊：
影响因子：
8.3
通讯作者：
Weijian Zhou;A. Priller;J. Beck;Wu Zhengkun;Chen Maobai;A. Zhisheng;W. Kutschera;Xian Feng
中科院分区：
文献类型：
--
作者：
Weijian Zhou;A. Priller;J. Beck;Wu Zhengkun;Chen Maobai;A. Zhisheng;W. Kutschera;Xian Feng
宇宙成因放射性核素10Be是由宇宙射线在地球大气层中散裂产生的。它的产生速率受地磁场强度的调节，因此它在风沙沉积物中的积累速率原则上可以用来获得高分辨率的地磁场变化记录。然而，10Be大气降落率也根据降雨率的不同而在局部地区有所不同。10Be在沉积物中的积累速率由于10Be叠加了地磁和降水信号而变得更加复杂，10Be附着在过去某个时间从大气中落下的可再活化的尘埃上。在这里，我们证明了这些信号可以去卷积，从而在中国黄土长达8万年的10Be记录中得到亚洲季风强度的地磁场强度和古降水记录。我们得出的古地磁强度记录与SINT 200(Guyodo And Valet 1996)和Napis 75(Laj et al.2002)叠加的海洋记录表明，这种方法可能被用来从黄土中产生数百万年长的古地磁强度记录。这项技术还揭示了一种从大陆内陆地区提取定量古沉淀记录的新方法。我们得到的降水记录与基于洞穴δ18O的古亚洲季风强度记录大体相似(袁等人)。2004)和Hulu(Wang等人2001)洞穴，这表明古亚洲季风强度可能是对北半球和南半球太阳辐射强迫的共同响应。
The cosmogenic radionuclide 10Be is produced by cosmic-ray spallation in Earth's atmosphere. Its production rate is regulated by the geomagnetic field intensity, so that its accumulation rate in aeolian sediments can, in principle, be used to derive high-resolution records of geomagnetic field changes. However, 10Be atmospheric fallout rate also varies locally depending on rainfall rate. The accumulation rate of 10Be in sediments is further complicated by overprinting of the geomagnetic and precipitation signals by 10Be attached to remobilized dust, which fell from the atmosphere at some time in the past. Here, we demonstrate that these signals can be deconvoluted to derive both geomagnetic field intensity and paleoprecipitation records of Asian Monsoon intensity in an 80,000-yr-long 10Be record from Chinese loess. The strong similarity between our derived paleomagnetic intensity record and the SINT 200 (Guyodo and Valet 1996) and NAPIS 75 (Laj et al. 2002) stacked-marine records suggests that this method might be used to produce multimillion-yr-long records of paleomagnetic intensity from loess. This technique also reveals a new method for extracting quantitative paleoprecipitation records from continental interior regions. Our derived precipitation record is broadly similar to the speleothem δ18O-based records of paleo-Asian Monsoon intensity from Dongge (Yuan et al. 2004) and Hulu (Wang et al. 2001) caves, and suggests that the paleo-Asian Monsoon intensity may be responding to a combination of both Northern and Southern Hemisphere insolation forcing.