Geomagnetic Field Reversals in the Palaeozoic and Cenozoic: Palaeomagnetic Evidence from Russia and Turkmenia

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The aim of this project is the investigation of Palaeozoic and Ceonozoic geomagnetic reversals. Using palaeomagnetism, the morphology of these reversals and main features, e.g. duration of the process, mode of the geomagnetic component changes, symmetry (or asymmetry) of the process with respect to polarity and time, will be studied. Late Permian reversals recorded in sedimentary sequences of the Volga-Viatka region (eastern part of the Russian platform) will be studied. These reversals are of particular significance as they mark the transition from a long-lasting reversed polarity superchron (PCRS or Kiaman superchron) to the rapidly changing field of Permo-Triassic times. Furthermore, few data are as yet available for field reversals of pre-Cenozoic age. Polarity transitions will also be studied in Plio-Pleistocene marine sediments of the Lopet-Dagh foothills, western Turkmenistan. These sequences span the entire Matuyama polarity chron and the transiton to the present day Bruhnes normal polarity chron. All the proposed sections are known to carry primary directions of magnetisa- tion. From palaeomagnetic studies it will be possible to determine the variations in magnetic direction recorded by the sediments during a number of different reversals from different geological time-periods. This will allow characterisation of the dipolar versus non-dipolar field features of the Earth`s magnetic field and whether or not there are systematic patterns in the VGP longitudes during magnetic reversals. Relative palaeo-intensity measurements will enable characterise the total transition time for polarity transitions as recorded in oscillations of the palaeofield intensity prior, during and after the polarity transitions. This will yield vital information with regards to the stability of the geodynamo, and provide a test for the various models which have been proposed.