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

• Applicant: Professor Dr. Valerian Bachtadse
• Subject Area: Geophysics
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 81200316

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.

• DFG Programme: Research Grants
• Participating Person: Privatdozentin Dr. Angela Bruch