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

亚美尼亚的更新世地质主要是湖泊沉积物的广泛存在，证明至少在过去200万年里环境条件反复发生迅速和剧烈的变化。这些沉积物中含有大量的各种化石遗迹，可以重建植物群、动物群以及气候条件，特别是在早期人类（如Homo georgicus）（1.8 Ma）向欧亚大陆扩散期间。然而，不幸的是，这些序列的精确测年仍然是一个有争议的问题，迄今为止唯一可用的绝对年龄来自覆盖在湖相辉长岩上的玄武岩，范围从1.2到0.935 Ma。针对年龄争论，在Sisian镇附近的Vorotan河地区进行了详细的磁性地层学试点研究，迄今为止，合作调查员共获得了250个定向岩心。采样覆盖了5个剖面，地层厚度约70米。详细的古地磁分析表明，在一个以逆磁化作用为主的序列中存在一个正极性带。这些结果，结合湖泊沉积物的沉积速率估计，初步解释，以反映奥杜威正常亚时内的松山时的反极性。如果这一解释被证明是可靠的，那么这项研究就代表着在确定序列的绝对年龄方面迈出了重要的一步。到目前为止，所研究的磁性材料质量极高，值得进一步取样，以增加样品密度。这将导致高分辨率的磁性地层学在过去的300万年，并提供了重要的贡献，这些沉积物在区域和全球范围内的对比。此外，对正常到反向和反向到正常转变的详细研究将产生关于地球磁场在磁场反转之前不久、期间和之后不久的精细结构的有价值的信息。该项目计划进行的研究还将涉及相对古强度以及对过去三百万年气候条件的岩石磁性代用指标的分析。将古地磁学和岩磁学研究与古生物学和古植物学相结合，将有助于全面了解小高加索地区早期人类活动的环境条件，并将对地球磁场的认识做出重要贡献。

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.