Establishing a Luminescence-Based Chronostratigraphy for the Last Glacial-Interglacial Cycle of the Loess-Palaeosol Sequence Achajur (Armenia)
Establishing a Luminescence-Based Chronostratigraphy for the Last Glacial-Interglacial Cycle of the Loess-Palaeosol Sequence Achajur (Armenia)
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DOI：
10.3389/feart.2021.755084
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
J. Lomax;D. Wolf;Urs Tilmann Wolpert;L. Sahakyan;H. Hovakimyan;D. Faust;M. Fuchs
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文献类型：
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作者：
J. Lomax;D. Wolf;Urs Tilmann Wolpert;L. Sahakyan;H. Hovakimyan;D. Faust;M. Fuchs
Achajur 黄土-古土壤剖面是亚美尼亚东北部 Sevkar 黄土地区的一部分，由三个带有夹层黄土单元的突出土壤复合体组成，可能跨越至少三个冰期-间冰期旋回。塞夫卡黄土区地处黑海和里海之间的中心位置，是东南欧黄土地段与中亚黄土地段之间的重要桥梁。建立阿恰珠尔黄土剖面的数值年代学可以与其他黄土-古土壤剖面进行关联，并重建该地区的古环境。在本文中，我们利用细粒（4-11 µm）材料的发光测年技术，重点研究最后一次冰期-间冰期循环的年代学。我们比较了使用不同刺激温度对多矿物细粒进行的两种后 IR-IRSL 方案，以评估褪色和潜在不可漂白残留物对我们样品的影响。为了备份较年轻的年龄（<50 ka），我们还在石英细粒部分上应用了单等分方案。结果表明，上部黄土单元在 MIS3 和 4 时期沉积，而 MIS2 年龄不存在。底层土壤复合体和黄土单元分别属于 MIS5 和 MIS6。这证实了黄土是在干燥阶段沉积的，而土壤复合体是在湿润阶段形成的，与该地区其他古环境指标的比较也表明了这一点。
The loess-palaeosol section Achajur is part of the Sevkar loess area in north-eastern Armenia and comprises three prominent pedocomplexes with intercalated loess units, probably spanning at least three glacial-interglacial cycles. With its central position between the Black Sea and the Caspian Sea, the Sevkar loess area serves as important bridge between loess sections in southeastern Europe and Central Asia. Establishing a numerical chronology of the Achajur loess section enables correlation with other loess-palaeosol sections and a palaeoenvironmental reconstruction of the region. In this paper, we focus on the chronology of the last glacial-interglacial cycle using luminescence dating on fine grain (4–11 µm) material. We compare two post-IR-IRSL protocols on polymineral fine grain using different stimulation temperatures, in order to evaluate the influence of fading and potential unbleachable residuals on our samples. For a backup of the younger ages (<50 ka), we also applied a single aliquot protocol on the quartz fine grain fraction. The results indicate that the upper loess unit was deposited during MIS3 and 4, while MIS2 ages are not present. The underlying pedocomplex and loess unit fall into MIS5 and MIS6, respectively. This confirms that the loess was deposited during dry phases and pedocomplexes formed during wetter phases, as is also shown by comparison with other palaeoenvironmental proxies from the area.