Paläomagnetische Quantifizierung neogener Blockrotationen an einer aktiven, transtensionalen Plattengrenze, Baja California, Mexiko

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Compared to oceanic plate boundaries which are generally narrow zones of deformation, continental plate boundaries appear as widespread areas with complex and poorly understood kinematics. Motion of crustal blocks within these “diffuse plate boundaries” causes rather small-scale lithospheric deformation within the boundary zone, while the main plates behave more rigid. Complex deformation patterns of interacting terranes separated by a variety of active faults are the consequence. To study the dynamic implications of boundary zone deformation we suggest the Baja California peninsula, Mexico (Baja), as an ideal target and propose a detailed paleomagnetic study. Up to now, little paleomagnetic work directed toward vertical axis rotations has been done in Baja California, despite its location in a major active transtensional zone. To address this problem, it is planned to use classical paleomagnetic methods to study volcanic and sedimentary rocks ranging in age from 0 to 25m.y. located in areas where the faulting rates have been defined on geologic and Quaternary time scales. The analysis of paleomagnetic declinations and comparison to coeval data from North America and stable areas of Baja California will allow us to evaluate the long-term kinematics of the region and the effects of oblique-rifting in the Gulf of California to the east. The results of these investigations will be compared to geodetic measurements from Global Positioning System (GPS) with the aim to assess whether long-term motion deduced from paleomagnetic studies is coherent with the current deformation patterns derived from GPS data and extrapolation backward in time is possible. The new paleomagnetic data to be expected during the duration of the project will provide important parameters when defining the geodynamic evolution of Baja California and shed new light on the kinematics within a diffuse plate boundary.