Dissecting the Jurassic monster polar shift: Paleomagnetic analyses of Middle–Late Jurassic sedimentary rocks from Ethiopia

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We propose to investigate the largest, fastest, and least studied event of global plate motion of the last 300 million years, which is referred to as the ‘Jurassic monster polar shift’ (JUMPS). According to a preliminary selection of key paleomagnetic poles from the literature, from 160 to 148 Ma the continents bordering the Atlantic and the Pacific plate underwent a simultaneous clockwise rotation of 30° around a common equatorial Euler pole located near the Bay of Benin (offshore west Africa). Several major sedimentary basins worldwide responded to the associated changes in paleolatitude by adjusting their depositional style and architecture when shifting across zonal climate belts, for example from the equatorial belt of high humidity and primary productivity to the tropical arid belts of high aridity and low productivity. Some of the vastest reservoirs of natural resources that fuel the modern technological world may have originated as consequence of this motion. In this project, we propose to investigate and dissect the JUMPS (now based on a very limited data inventory) by means of paleomagnetic analyses of two marine sedimentary sections exposed near Addis Ababa (Ethiopia, North-east Africa). This cratonic area is an ideal locus for solving this tectonic problem because of its minimal longitudinal movement since Gondwana breakdown, plate-circuit-connection with the other major continental area, and presence of expanded and complete Middle-Upper Jurassic sedimentary sections that can provide high quality paleomagnetic dataset. The two target sections, namely the Mekele section and the Mugher section, are respectively ~660 m and ~160 m thick, and span a time interval between the Bathonian and the Tithonian, from about 165 to 145 Ma, straddling the time encompassed by the JUMPS. A total of 9 sites will be sampled for paleomagnetic analyses. Positive results will provide 5 new paleomagnetic poles across the whole extension of the JUMPS. The existing age of the sampled sites will be refined by paleontological analyses of cooperating partners. The acquired paleomagnetic dataset will be analyzed with cutting-edge statistical methods, which will significantly increase its reliability. All acquired data will have to be merged into a new global APWP in order to provide an innovative perspective of the JUMPS. The final result will be the creation of a series of paleogeographic maps that will include all constraints generated within the project. Up to date, virtually all published paleogeographic reconstructions that we use for the Jurassic do not include the effects of the JUMPS, and are therefore flawed. The paleomagnetic data retrieved in this project will be combined with the most recent compilation of Euler poles and reciprocal rotations for all continents in order to build a new global Jurassic paleogeography that will be of wide use in several disciplines of Earth Sciences.