Middle to Late Pleistocene environments based on stable organic carbon and nitrogen isotopes of loess‐palaeosol sequences from the Carpathian Basin
Middle to Late Pleistocene environments based on stable organic carbon and nitrogen isotopes of loess‐palaeosol sequences from the Carpathian Basin
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DOI：
10.1111/bor.12470
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发表时间：
2020-10
期刊：
影响因子：
2.2
通讯作者：
Stephan Pötter;A. Schmitz;A. Lücke;P. Schulte;Igor Obreht;M. Zech;H. Wissel;S. Marković;F. Le
中科院分区：
文献类型：
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作者：
Stephan Pötter;A. Schmitz;A. Lücke;P. Schulte;Igor Obreht;M. Zech;H. Wissel;S. Marković;F. Le
稳定的有机碳和氮同位素可用于解释过去的植被模式和生态系统质量。在这里，我们提出了来自喀尔巴阡盆地南部的两个黄土-古土壤序列的代理，以重建过去 350 ka 的古环境并建立区域共性和差异。此前，对该地区黄土序列的同位素研究仅针对末次冰期沉积物进行。我们进行了方法学测试，涉及在稳定同位素分析之前对样品进行完全脱钙。测试了两种脱钙方法（熏蒸法和湿化学酸化）、不同的处理时间以及碳同位素分析的重现性。所得结果表明，脱钙方法的选择对于黄土-古土壤序列的有机碳稳定同位素分析很重要，因为湿化学法和熏蒸法之间的比率相差超过10‰，因为后者碳酸盐去除不完全。因此，我们建议在黄土-古土壤序列研究中避免采用熏蒸方法。此外，我们的数据表明，TOC 含量<0.2% 的样品其碳同位素比率被误解的可能性更大。对于我们的地点，C3 植被占主导地位，并且在中更新世至晚更新世期间没有检测到导致主要光合作用途径发生变化的古环境变化。此外，强调了进一步稳定氮同位素研究的重要性，因为该代理似乎反映了过去的降水模式，并揭示了喀尔巴阡盆地南部的有利条件，特别是在间质期间。
Stable organic carbon and nitrogen isotopes can be used to interpret past vegetation patterns and ecosystem qualities. Here we present these proxies for two loess‐palaeosol sequences from the southern Carpathian Basin to reconstruct the palaeoenvironment during the past 350 ka and establish regional commonalities and differences. Before now, isotopic studies on loess sequences from this region were only conducted on deposits from the last glacial cycle. We conducted methodological tests involving the complete decalcification of the samples prior to stable isotope analyses. Two decalcification methods (fumigation method and wet chemical acidification), different treatment times, and the reproducibility of carbon isotope analyses were tested. Obtained results indicate that the choice of the decalcification method is important for organic carbon stable isotope analyses of loess‐palaeosol sequences because ratios vary by more than 10‰ between the wet chemical and fumigation methods, due to incomplete carbonate removal by the latter. Therefore, we suggest avoiding the fumigation method for studies on loess‐palaeosol sequences. In addition, our data show that samples with TOC content <0.2% bear increased potential for misinterpretation of their carbon isotope ratios. For our sites, C3‐vegetation is predominant and no palaeoenvironmental shifts leading to a change of the dominant photosynthesis pathway can be detected during the Middle to Late Pleistocene. Furthermore, the importance of further stable nitrogen isotope studies is highlighted, since this proxy seems to reflect past precipitation patterns and reveals favourable conditions in the southern Carpathian Basin, especially during interstadials.