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

该项目的目的是调查古生代和新生代地磁反转。利用古地磁，将研究这些逆转的形态和主要特征，如过程的持续时间、地磁分量变化的方式、过程相对于极性和时间的对称性(或不对称性)。将研究伏尔加-维亚特卡地区(俄罗斯地台东部)沉积序列中记录的晚二叠世反转。这些逆转具有特别重要的意义，因为它们标志着从持久的反转极性超级计时器(PCRS或Kiaman超级计时器)过渡到快速变化的二叠纪-三叠纪时代。此外，到目前为止，还没有多少资料可以用于前新生代的野外反转。还将研究土库曼斯坦西部洛佩特-达格山麓的上更新世海洋沉积物中的极性转变。这些序列跨越整个Matuyama极性计时器，并过渡到今天的Bruhnes正常极性计时器。所有提议的截面都带有主要的磁化方向。从古地磁研究中，将有可能确定沉积物在不同地质时期的若干不同反转过程中记录的磁方向的变化。这将使我们能够描述地球磁场的偶极和非偶极场特征，以及在磁逆过程中VGP经度是否存在系统的模式。相对的古强度测量将能够表征极性转变的总转变时间，如在极性转变之前、期间和之后的古场强度振荡中记录的那样。这将提供有关地球发电机稳定性的重要信息，并为已提出的各种模型提供测试。

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.