On the Early Permian shape of Pangea from paleomagnetism at its core

• Published in: Gondwana research Vol. 90; pp. 171 - 198
• Main Authors: Domeier, Mathew, Font, Eric, Youbi, Nasrrddine, Davies, Joshua, Nemkin, Samantha, Van der Voo, Rob, Perrot, Morgann, Benabbou, Mohamed, Boumehdi, Moulay Ahmed, Torsvik, Trond H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-02-2021
• Subjects: Paleogeography; Paleomagnetism; Pangea; Permian; Tectonics; Pangea; Permian; Paleogeography; Tectonics; Paleomagnetism
• ISSN: 1342-937X; 1878-0571
• DOI: 10.1016/j.gr.2020.11.005

Although central to an understanding of Earth's paleogeography and the myriad processes that it affects, the geometry of Pangea during the early phase of its lifetime has remained a topic of contention since the plate tectonic revolution. Despite decades of analysis and discussion, the crux of this debate still largely hinges on sparse, legacy paleomagnetic data derived from early Permian rocks of the Moroccan Meseta. In this work, we present the results of a study designed to revisit, update and expand on those key data, with the provision of new geochronologic and paleomagnetic results from six Permo-Carboniferous basins in central Morocco. New U-Pb zircon ages from volcanic rocks substantiate and refine existing geochronological data and reveal that volcanism among the studied basins spanned approximately 30 Ma, from at least 305 to 277 Ma, but was possibly punctuated by a more intense pulse in the mid-early Permian (~285 Ma). These new U-Pb data furthermore suggest that the age estimates previously assigned to the key poles from the Moroccan Meseta are probably too young, by some ~10 Ma. New paleomagnetic results from six basins yielded a common, well-defined remanent magnetization from 20 sites that is demonstrated to be pre-middle Permian in age. However, it remains unclear whether this magnetization (which is directionally similar to the previous paleomagnetic data from the same basins) is a primary magnetization acquired at ~285 Ma, or a syn-folding remagnetization that was acquired shortly thereafter, at ~275 Ma. In adopting both interpretations as alternative hypotheses, we examine the corresponding paleogeographic implications of both. Through exhaustive comparisons with reference apparent polar wander paths and the direct reconstruction of Gondwana using these new paleomagnetic results, we demonstrate that in either case (i.e. whether the remanent magnetization is primary or was acquired soon after during folding) the data is compatible with a Pangea A geometry during the early Permian. We close with a topical discussion of some persisting arguments used to defend Pangea B and why we consider them to be flawed.
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•New U-Pb age constraints on early Permian volcanics in central Morocco.•New paleomagnetic data constrain paleolatitude of Gondwana in early Permian.•Geometry of Pangea in early Permian is consistent with Pangea A.