Paleomagnetism of Permian Basins in Morocco - A Contribution to Late Paleozoic Geodynamivs in the Western Mediterranean

• Applicant: Professor Dr. Valerian Bachtadse
• Subject Area: Geophysics ; Palaeontology
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 374919867

The exact configuration of Pangea during Permian times is still a matter of debate. Espe-cially the question whether the continental overlap of more than 1.000km between Gondwana and Laurentia in classical Pangea reconstructions which are based on paleomagnetic data is still debated in a very controversial way. Accepting this continental misfit as real ,the overlap can be overcome by shifting Gondwana some 3000km to the east (Pangea B). This move does not violate the fundamental laws of paleomagnetism, but requires a mega shear zone in order to transfer Gondwana into the Pangea A configuration prior to the opening of the Atlantic ocean. Although, recent paleomagnetic studies in Sardinia and the Toulon- basin have demonstrated that such a mega-shear zone might have existed it has not been generally accepted and opponents of Pangea B have argued that the continental overlap is an artifact and due to inclination shallowing, a post sedimentary process by which the paleomagnetic inclination is flattened and the paleolatitude at which the magnetization has been acquired is falsified signifi-cantly. Applying a blanket correction for inclination shallowing to all sedimentary paleomagnetic data used for palaeogeographic reconstructions reduces rmoves the overlap but whether this procedure is appropriate is not clear. The Permo-Carboniferous sedimentary basins of Morocco, especially of the Meseta, play a key role for Pangea reconstructions. High quality paleomagnetic data for Gondwana for Permian times are rather scarce and paleomagnetic studies of the sedimentary and volcanic rocks exposed here have very high potential to significantly improve this situation and to lead to a more robust paleogeographic reconstruction. The stratigraphy of many of these basins is controlled by red beds of various grain sizes and intercalated volcanic rocks which achieve significant thicknesses. By careful and detailed paleo- and rock magnetic studies it is possible to identify the carriers of magnetization in these red beds (pigmentary and/or sedimentary hematite) and by the use of competing methods to determine the degreeof inclination shallowing, if any, in the latter. Comparison of the mean directions obtained for sediments to those from volcanic rocks directly below or above the sediments allows a test of the reliabilty of these methods. Parallel to the analysis of inclination data, the study aims at identification of rotational movements of the Permian basins comparable to the ones observed in Sardinia and southern France. The identification of rotations about vertical axis will yield additional support to the existence of a mega shear zone and declinations taken together with high quality inclination data will allow a robust reconstruction of Gondwana during Permian times.

• DFG Programme: Research Grants