Luminescence dating of the Stratzing loess profile (Austria) – Testing the potential of an elevated temperature post-IR IRSL protocol
Luminescence dating of the Stratzing loess profile (Austria) – Testing the potential of an elevated temperature post-IR IRSL protocol
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DOI：
10.1016/j.quaint.2010.05.018
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发表时间：
2011-04
影响因子：
2.2
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长石红外受激发光信号在∼2000Gy处饱和，即∼500Gy700Ga(假设剂量率为3-4Gyka/ka，典型的黄土)，因此理论上可以确定中更新世黄土的年龄。然而，年龄估计的准确性受到异常衰落的阻碍，这导致了对年龄的严重低估。已经提出了褪色修正，但这些修正依赖于固有的假设，在任何情况下都不适用于大剂量(随着生长曲线接近饱和)。最近的研究已经确定了一种后IR IRSL信号，它表现出较少的衰落，因此对准确的衰落校正的依赖程度较低。这项研究建立在这些研究的基础上，并将后IR IRSL SAR测年协议应用于下奥地利层序的黄土/古土壤序列的多矿物细粒样品。在320°C(S 60°C)预热和50°C(S 200°C)IR漂白剂预热后，在290°C下测量S 200℃的IRSL；使用相同的条件来测量对测试剂量的响应。回收比、恢复和剂量恢复试验表明，该方案适用于所调查的黄土，尽管观察到高达20Gy射线的有限剩余剂量。对于最老的样本，自然信号处于或接近饱和，这表明衰落在本质上可以忽略不计。这一观察结果与实验室测量的1-1.5%/十年的衰落速率不一致，需要进一步研究。
Feldspar infrared stimulated luminescence (IRSL) signals saturate at ∼2000 Gy, i.e. ∼500–700 ka (assuming a dose rate of 3–4 Gy/ka, typical for loess) and it is therefore theoretically possible to date Middle Pleistocene loess. However, the accuracy of age estimates is hampered by anomalous fading, which leads to significant age underestimation. Fading corrections have been proposed but these corrections are reliant on inherent assumptions and in any case are inapplicable at large doses (as the growth curve approaches saturation). Recent studies have identified a post-IR IRSL signal that shows less fading and is thus less dependent on accurate fading corrections. This study builds upon these investigations and applies a post-IR IRSL SAR dating protocol to polymineral fine-grain samples of the loess/palaeosol sequence in Stratzing, Lower Austria. After a preheat at 320 °C (60 s) and an IR bleach at 50 °C (200 s) IRSL was measured at 290 °C for 200 s; the same set of conditions were used to measure the response to a test dose. Recycling ratios, recuperation and dose recovery tests show that this protocol is suitable for the loess under investigation, although finite residual doses of up to 20 Gy are observed. For the oldest samples, the natural signal is in, or close to, saturation, indicating that fading is negligible in nature. This observation is inconsistent with the measured laboratory fading rates of 1–1.5%/decade and needs further investigation.