Magnetostratigraphy of Plio-Pleistocene Lake Sediments from Armenia (Magnetostratigraphie Plio-Pleistozäner Seesedimente aus Armenien)

亚美尼亚普利翁-更新世湖沉积物的磁性地层学

• 批准号: 81200316
• 负责人: Professor Dr. Valerian Bachtadse
• 金额: --
• 依托单位: Sektion Geophysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2010-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/81200316?language=en
• 关键词: Magnetostratigraphy; Plio; Pleistocene; Lake; Sediments

The Pleistocene geology of Armenia is dominated by the widespread occurrence of lake sediments testifying repeated rapid and drastic changes of the environmental conditions during at least the last 2 million years. These sediments contain a huge variety of various fossil remains allowing the reconstruction of flora, fauna as well as the climatic conditions especially during dispersal of early man like homo georgicus (1.8 Ma) into Eurasia. Unfortunately, however, precise dating of these sequences is still a matter of debate and the only absolute ages available up to date have been derived from basalts overlaying the lacustrine diatomites and ranging from 1.2 to 0.935 Ma. Addressing the age debate, a detailed magnetostratigraphic pilot study has been carried out in the Vorotan river area near the town of Sisian, where a total number of 250 orientated drill cores has been obtained so far by the co- investigator. Sampling covered 5 sections with roughly 70 meters in stratigraphic thickness. Detailed palaeomagnetic analysis reveals the presence of a zone of normal polarity within a sequence which is dominated by inverse magnetizations. These results, in combination with estimated sedimentation rates for lake sediments, are tentatively interpreted to reflect the Olduvai normal subchron within the Matuyama chron of inverse polarity. If this interpretation proves to be robust, this study represents a major step forward in assigning absolute ages to the sequence. The extremely high quality of the material studied so far magnetically merits further sampling in order to increase the sample density. This will result in a high resolution magnetostratigraphy for the last 3 million years and provide important contributions for correlation of these sediments on regional and global scales. Furthermore, detailed studies of the Normal to Reverse and Reverse to Normal transitions will yield valuable information with regards to the fine structure of the Earth s magnetic filed shortly before, during and shortly after field reversals. The studies planned in this project will also address relative palaeointensities as well as analysis of rockmagnetic proxies for climate conditions during the last three million years. Combining palaeomagnetic and rockmagnetic studies with palaeontology and palaeobotany will result in a comprehensive picture of the environmental conditions during the occurrence of early man in the Lesser Caucasus and furthermore, significantly contribute to the understanding of the Earth s Magnetic Field.

亚美尼亚的更新世地质以湖泊沉积物的广泛发生为主，证明了至少在过去的200万年中反复发生的环境条件的快速变化和急剧变化。这些沉积物中包含各种各样的化石仍然存在，可以重建动植物，动物区系以及气候条件，尤其是在分散早期男子（如Homo Georgicus（1.8 MA））中的气候条件。但是，不幸的是，这些序列的精确约会仍然是一个争论的问题，并且唯一可用的最新年龄是从覆盖湖间硅藻的玄武岩中得出的，范围为1.2至0.935 mA。在解决年龄辩论时，已经在西西安镇附近的Vorotan河地区进行了一项详细的磁层试验研究，迄今为止，合作社已经获得了250个取向的钻芯。采样涵盖了5个部分，大约70米的地层厚度。详细的古磁分析揭示了以逆磁性为主的序列中存在正常性区域。这些结果与湖泊沉积物的估计沉积率相结合，进行了暂定解释，以反映逆极性的Matuyama Chron内的Olduvai正常子同胞。如果这种解释被证明是鲁棒的，那么这项研究代表了将绝对年龄分配给序列的重要一步。到目前为止，研究的材料的极高质量在磁性上值得进一步采样，以增加样品密度。这将导致在过去300万年中产生高分辨率的磁层学，并为这些沉积物在区域和全球尺度上的相关性提供重要贡献。此外，对逆转正常和反向正常过渡的详细研究将就野外逆转前不久，期间和之后提交的地球磁体的精细结构而产生有价值的信息。该项目计划中计划的研究还将解决过去三百万年内为气候条件的岩石磁性代理分析。将古磁和岩石磁研究与古生物学和古植物学相结合，将全面了解早期男子在较小的高加索地区发生的环境条件，并在此外显着有助于理解地球磁场。