A comparison of OSL ages derived from silt-sized quartz and polymineral grains from Chinese loess
A comparison of OSL ages derived from silt-sized quartz and polymineral grains from Chinese loess
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DOI：
10.1016/s0277-3791(03)00053-2
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发表时间：
2003-05
影响因子：
4
通讯作者：
T. Watanuki;A. Murray;S. Tsukamoto
中科院分区：
文献类型：
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作者：
T. Watanuki;A. Murray;S. Tsukamoto
最近的工作(Watanuki等人提交)通过与独立的年龄控制相比较表明，从日本黄土中提取的粉砂大小的石英颗粒可以用于高达425Gy光激发发光测年(这些地点的∼为500ka)。与红外(IR)激发和红外后蓝激发OSL的进一步比较表明，后者给出了准确的年龄，可能以石英为主，而前者系统地低估了30-600ka的年龄，并在实验室测试中显示出衰退。在日本，黄土沉积的主要来源是中国大陆；在东亚，盛行的西风使黄土广泛分布，其中主要来源之一是中国的西部荒漠地区。不幸的是，在中国的黄土沉积物中，独立的年龄控制是非常不寻常的，而且几乎没有证据表明这种材料现有的发光年龄的准确性。作为一种替代方法，本研究以日本的结果为基础，利用中国两个地点的黄土，考察了多矿物样品的单等分再生剂量IR和红外后蓝光激发发光年龄与蓝激发石英发光年龄的关系。来自东部的石英的归一化蓝光激发光致发光强度大约是来自西部的10倍，这表明要么是来自不同的物质来源，要么(不太可能)是石英的灵敏度随着输运距离的增加而增加。通过与石英结果的比较，我们得出结论：在我们的黄土样品中，红外后蓝激发的光激发光信号比红外信号是更可靠的多矿物信号。尽管如此，它可能包括长石成分，这应该通过实验室褪色实验进行测试。
Recent work (Watanuki et al., submitted) has shown by comparison with independent age control that silt-sized quartz grains extracted from Japanese loess can be used for optically stimulated luminescence (OSL) dating for equivalent doses of up to 425Gy (∼500ka at these sites). Further comparison with infrared (IR) stimulated and post-IR blue-stimulated OSL showed that the latter signal gave accurate ages, and was probably dominated by quartz, whereas the former systematically underestimated ages in the range 30–600ka, and showed fading in laboratory tests. The main source of the loess deposits in Japan is the Chinese mainland; in eastern Asia, loess is widely distributed by the prevailing westerly winds, and one of the main sources is in the western desert areas of China. Unfortunately, independent age control is very unusual in loess deposits in China, and there is little evidence for the accuracy of existing luminescence ages from this material. As an alternative approach, this study builds on the Japanese results by using loess from two Chinese sites, and examining the relationship between single-aliquot regeneration dose IR and post-IR blue-stimulated luminescence ages from polymineral samples, and blue-stimulated quartz luminescence ages. The normalized blue-stimulated OSL intensity from quartz from the eastern site was about 10 times that from the west, suggesting either a different source of material, or (less likely) an increase in quartz sensitivity with transport distance. By comparison with quartz results we conclude that, in our samples of Chinese loess, the post-IR blue-stimulated OSL is the more reliable polymineral signal, when compared with the IR signal. It may nevertheless include a feldspar component, and this should be tested for using laboratory fading experiments.