Constraints on the Ediacaran inertial interchange true polar wander hypothesis: A new paleomagnetic study in Morocco (West African Craton)

•Identification of a 90° Ediacaran oscillation of poles in volcanic series of Morocco.•Observation of a similar pattern in reappraised APWPs of Laurentia and Baltica.•Plate reconstructions inferred by our data in agreement with the geodynamic context.•Interpretation of this large global polar motion...

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Bibliographic Details
Published in:	Precambrian research Vol. 295; pp. 90 - 116
Main Authors:	Robert, B., Besse, J., Blein, O., Greff-Lefftz, M., Baudin, T., Lopes, F., Meslouh, S., Belbadaoui, M.
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-07-2017 Elsevier
Subjects:	Earth Sciences Ediacaran Equatorial dipole Laurentia Paleomagnetism Sciences of the Universe True Polar Wander West African craton Ediacaran Equatorial dipole Laurentia Paleomagnetism West African craton True Polar Wander
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Summary:	•Identification of a 90° Ediacaran oscillation of poles in volcanic series of Morocco.•Observation of a similar pattern in reappraised APWPs of Laurentia and Baltica.•Plate reconstructions inferred by our data in agreement with the geodynamic context.•Interpretation of this large global polar motion in terms of a large IITPW episode. We conducted a paleomagnetic study on late Ediacaran and early Cambrian volcanic deposits and lava flows from the Ouarzazate and Taroudannt groups in the Anti-Atlas, Morocco. Four stable magnetic mean directions have been isolated using thermal demagnetization technique. A first component “A” is most probably a remagnetization acquired during the Hercynian related tectonic phases, and yields a paleomagnetic pole (λ=−29.3° N, ϕ=56.6° E, A95=4.1°) indistinguishable from the 330–300Ma segment of the Gondwana apparent polar wander path (APWP). The Cambrian Djebel Boho formation of the Taroudannt group and the Ediacaran Tadoughast and Fajjoud formations of the Ouarzazate group yield two poles of similar directions respectively “B1” (λ=21.9°N, ϕ=31.0°E, A95=15.6°) and “B2” (λ=27.3°N, ϕ=27.1°E, A95=14.9°). In the Adrar-n-Takoucht formation (oldest part of the Ouarzazate group), another component is observed, yielding a paleomagnetic pole “C” (λ=−57.6°N, ϕ=295.6°E, A95=15.7°). The primary nature of these last three magnetizations is supported by paleomagnetic tests and we interpreted them as magnetizations acquired during or shortly after the deposit of volcaniclastics or emplacement of lava flows. Using these new data, we reappraised the West African Craton (WAC) APWP and found two large paleomagnetic shifts of some 90°, the first one between 615 and 571Ma and the second one between 571 and 565Ma. A comparison with already published paleomagnetic data from Laurentia, Baltica and Gondwana, along with a discussion on their paleogeographic relationships, showed that our WAC APWP loop is likely recorded in the APWP’s of these blocks. The superimposition of these APWP’s leads to a geologically consistent paleogeography which may be explained by two rapid inertial interchange true polar wander even if we cannot exclude that magnetic field perturbations may have also occurred during the Ediacaran.
ISSN:	0301-9268 1872-7433
DOI:	10.1016/j.precamres.2017.04.010