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

亚美尼亚更新世地质以广泛存在的湖泊沉积物为主导，证明了至少在过去200万年中环境条件的反复快速和剧烈变化。这些沉积物中含有种类繁多的化石遗迹，可以重建植物群、动物群以及气候条件，特别是在像乔治人（1.8 Ma）这样的早期人类扩散到欧亚大陆期间。然而，不幸的是，这些序列的精确年代仍然是一个有争议的问题，迄今为止唯一可用的绝对年龄是从覆盖在湖硅藻土上的玄武岩中得出的，范围从1.2到0.935 Ma。为了解决年龄的争论，在Sisian镇附近的Vorotan河地区进行了详细的磁地层学初步研究，到目前为止，共同研究者已经获得了250个定向岩心。采样覆盖5个剖面，地层厚度约70米。详细的古地磁分析表明，在一个以逆磁化为主的层序中存在一个正常极性带。这些结果结合湖泊沉积物的沉积速率估计，初步解释为在反极性的Matuyama年表中反映了Olduvai正常亚时。如果这一解释被证明是可靠的，那么这项研究代表着在确定序列的绝对年龄方面迈出了重要的一步。迄今为止所研究的材料具有极高的磁性，值得进一步取样以增加样品密度。这将产生近300万年的高分辨率磁地层学，并为这些沉积物在区域和全球尺度上的对比提供重要贡献。此外，对正向倒转和从正向正转的详细研究将提供有关地磁倒转前不久、期间和之后不久地球磁场精细结构的宝贵信息。该项目计划的研究还将涉及相对古强度，以及分析过去300万年气候条件的岩石磁代用物。将古地磁、岩磁研究与古生物学、古植物学相结合，可以全面了解小高加索地区早期人类出现时的环境条件，对认识地球磁场具有重要意义。

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.