Radiocarbon dating of Loess-Palaeosol-Sequences from Remagen-Schwalbenberg using Earthworm Calcite Granules

使用蚯蚓方解石颗粒对雷马根-施瓦尔本贝格黄土-古土壤序列进行放射性碳测年

• 批准号: 439443769
• 负责人: Dr. Peter Fischer
• 金额: --
• 依托单位: Lehrstuhl für Geomorphologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/439443769?language=en
• 关键词: Radiocarbon; dating; Loess; Palaeosol; Sequences

In the frame of the DFG-funded TERRACLIME-project, precise dating of investigated Loess-Palaeosol-Sequences (LPS) from the Schwalbenberg near Remagen (Middle Rhine valley, Germany) is one of the major challenges. The Schwalbenberg is unique because it preserves a complete terrestrial record of Last Glacial climate variability in western Central Europe, and especially of Marine Isotope Stage (MIS) 3. In context to the documentation and interpretation of millennial-timescale warming periods, named Greenland Interstadials (GI) or Dansgaard-Oeschger events, and their impact on landscape formation the dating approach gains particular importance. The interstadial periods appear as soil horizons of different development degrees within the investigated sequences and can be traced precisely using the multi-proxy-approach elaborated for the TERRACLIME-project. In contrast, the exact chronostratigraphic position remains uncertain, especially due to unfavourable mineralogical characteristics and relatively large error ranges of luminescence ages, which partly exceed the duration of interstadial periods. In this context, a promising dating approach has recently been developed applying radiocarbon dating of fossil Earthworm Calcite Granules (ECG) that shows very promising results for the Nussloch type section and northwestern France (Moine et al., 2017; Prud’homme et al., 2019). This new approach is even more important as conventional 14C-datable remains are scarce in LPS hampering the development of robust radiocarbon chronologies. Within our preparatory studies, a new profile at the Schwalbenberg was prepared and sampled in high resolution (5 cm intervals, 105 samples in total). The profile is characterised by several brown soils, tundra gleys and loess deposits of MIS 3 age, showing particularly high numbers of ECG in palaeosols. First radiocarbon ages significantly improved the age model for the Schwalbenberg LPS and shows that the sampled material is suitable for 14C-dating. Thus, the main objective of this supplementary proposal is radiocarbon dating of additional 40 samples from the Schwalbenberg profile. The data will be integrated into the ongoing work of the TERRACLIME-project and help to validate luminescence ages and refine OSL protocols. Recently, isotope analyses (δ18O und δ13C) have already been conducted on all samples from the new profile. Based on these analyses and the complementary ECG dating approach, it will be possible to interpret essential palaeoclimate data against the background of a robust chronostratigraphy and to compare them to regional and global palaeoclimate archives.

在 DFG 资助的 TERRACLIME 项目框架中，对雷马根附近的施瓦尔本贝格（德国中莱茵河谷）所调查的黄土-古土壤序列（LPS）进行精确测年是主要挑战之一。施瓦尔本贝格是独一无二的，因为它保存了中欧西部末次冰期气候变化的完整陆地记录，特别是海洋同位素阶段（MIS）3。在记录和解释千年尺度变暖时期（称为格陵兰间质事件（GI）或丹斯加德-厄施格事件）及其对地貌形成的影响时，测年方法变得尤为重要。在所研究的序列中，间期表现为不同发育程度的土壤层，并且可以使用为 TERRACLIME 项目详细阐述的多代理方法进行精确追踪。相比之下，确切的年代地层位置仍然不确定，特别是由于不利的矿物学特征和相对较大的发光年龄误差范围，部分超过了间期的持续时间。在这种背景下，最近开发了一种有前途的测年方法，应用化石蚯蚓方解石颗粒（ECG）的放射性碳测年，该方法在努斯洛赫类型部分和法国西北部显示出非常有希望的结果（Moine等人，2017年；Prud'homme等人，2019年）。这种新方法更为重要，因为 LPS 中传统的 14C 年代测定遗骸很少，这阻碍了稳健的放射性碳年代学的发展。在我们的准备研究中，在 Schwalbenberg 准备了一份新的剖面图，并以高分辨率进行采样（间隔 5 厘米，总共 105 个样本）。该剖面的特征是一些棕色土壤、苔原隐隙和 MIS 3 年龄的黄土沉积物，在古土壤中显示出特别大量的 ECG。首次放射性碳年龄显着改进了 Schwalbenberg LPS 的年龄模型，并表明采样材料适合 14C 测年。因此，本补充提案的主要目标是对 Schwalbenberg 剖面中的另外 40 个样品进行放射性碳测年。这些数据将被整合到 TERRACLIME 项目正在进行的工作中，并有助于验证发光年龄和完善 OSL 协议。最近，已经对新剖面的所有样品进行了同位素分析（δ18O 和 δ13C）。基于这些分析和补充的心电图测年方法，将有可能在强大的年代地层学背景下解释基本的古气候数据，并将其与区域和全球古气候档案进行比较。