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

本项目的目的是研究古生代和新生代地磁倒转。利用古地磁，将研究这些逆转的形态和主要特征，例如过程的持续时间、地磁成分变化的模式、过程在极性和时间方面的对称性（或非对称性）。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。这些反转具有特殊的意义，因为它们标志着从一个长期的极性反转超时（PCRS或Kiaman超时）到快速变化的二叠纪-三叠纪领域的转变。此外，关于前新生代的地磁反转的资料还很少。极性转变也将在土库曼斯坦西部Lopet-Dagh山麓的上新世-更新世海洋沉积物中进行研究。这些序列跨越了整个Matuyama极性时线，并过渡到今天的bruhne正常极性时线。已知所有提出的剖面都带有主要的磁化方向。通过古地磁研究，将有可能确定沉积物在不同地质时期的若干次不同地磁倒转期间所记录的磁方向变化。这将允许描述地球磁场的偶极与非偶极场特征，以及在磁极反转期间VGP经度是否存在系统模式。相对古强度测量将能够描述极性转变的总转变时间，记录在极性转变之前、期间和之后的古磁场强度振荡中。这将产生关于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检验。

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.