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首页> 外文期刊>Journal of Asian earth sciences >Chronology and the upper dating limit for loess samples from Luochuan section in the Chinese Loess Plateau using quartz OSL SAR protocol
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Chronology and the upper dating limit for loess samples from Luochuan section in the Chinese Loess Plateau using quartz OSL SAR protocol

机译：利用石英OSL SAR协议对黄土高原洛川段黄土样品的年代学和上限日期

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Luminescence dating of loess older than 100 ka has long been a challenge. It has been recently reported that, using optically stimulated luminescence (OSL) of fine-grained quartz (4-11 μm) extracted from loess, the range of luminescence dating could be pushed to ～0.6 Ma with OSL ages being in agreement with independent ages [Watanuki, T., Murray, A.S., Tsukamoto, S., 2005. Quartz and polymineral luminescence dating of Japanese loess over the last 0.6 Ma: comparison with an independent chronology. Earth and Planetary Science Letters 240, 774-789]. The aim of this study is to provide a luminescence chronology (20 samples) for the standard Luochuan loess section, and to further examine the upper limit of quartz OSL dating for Chinese loess. The growth curve does not saturate at 700 Gy, and should allow reliable equivalent dose (D_e) determination up to at least 400 Gy. However, when compared with independent chronological control, the D_e that could be treated as reliable is less than ～230 Gy (corresponding to ～70 ka in age for Chinese loess), and the D_e larger than ～230 Gy should be underestimated. Ages for samples from the lower part of palaeosol SI are severely underestimated, with the maximum age of 95 ka for a sample from the bottom of this palaeosol, much younger than the expected age of ～128 ka. The maximum De obtained for sample L9/M, collected from loess layer L9 which is below the Matuyama-Brunhes (B/M) boundary whose age is ～780 ka, is only 403 Gy which corresponds to an age of 107 ka. The cause of underestimation is not yet clear. The previous results by Watunuki et al. (2005) on the extension of OSL dating of loess to 0.6 Ma is not confirmed. When evaluating the validity of OSL ages in SI, another possibility is to question the already established chronological frame for Luochuan section, which is based on the hypothesis of continuous dust deposition. The assumption of an erosion hiatus between L2 and SI could make the OSL ages look reasonable. However, if this is the case, then it is difficult to explain why the age of sample L9/M is only 107 ka which could be treated as a saturation age, while the OSL can provide a correct age for loess as old as 94.9 ka for sample LC22 collected from the bottom of SI. Much work is required to clarify these confusions.
机译：黄土的发光年龄大于100 ka一直是一个挑战。最近有报道称，利用从黄土中提取的细晶石英（4-11μm）的光激发发光（OSL），OSL年龄与独立年龄一致，发光测年范围可推至〜0.6 Ma。 [Watanuki，T.，Murray，AS，Tsukamoto，S.，2005。日本黄土在最近的0.6 Ma内的石英和多矿物发光年代：与一个独立的年代比较。地球与行星科学快报240，774-789]。这项研究的目的是为标准的洛川黄土剖面提供发光年表（20个样品），并进一步检查中国黄土石英OSL年代的上限。生长曲线在700 Gy时不会饱和，并且应该能够确定至少400 Gy的可靠等效剂量（D_e）。然而，与独立的时间控制相比，可以被认为是可靠的D_e小于〜230 Gy（相当于中国黄土的年龄为〜70 ka），而大于〜230 Gy的D_e应被低估。严重低估了古土壤SI下部样品的年龄，该古土壤底部样品的最大年龄为95 ka，比预期的〜128 ka年龄要年轻得多。从年龄在〜780 ka的Matuyama-Brunhes（B / M）边界以下的黄土层L9收集的样品L9 / M的最大De仅为403 Gy，相当于107 ka的年龄。低估的原因尚不清楚。 Watunuki等人的先前结果。 （2005年）关于黄土OSL测年延长至0.6 Ma的问题尚未得到证实。在评估SI中OSL年龄的有效性时，另一种可能性是质疑洛川断面已经建立的时间框架，该框架基于连续粉尘沉积的假设。 L2和SI之间存在腐蚀中断的假设可能使OSL年龄显得合理。但是，如果是这种情况，那么很难解释为什么样品L9 / M的年龄只有107 ka，可以视为饱和年龄，而OSL可以为94.9 ka的黄土提供正确的年龄。从SI底部收集的样品LC22。要澄清这些混乱，需要做大量工作。

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