Diachronous folding and cleavage in an intraplate setting (Central High Atlas, Morocco) determined through the study of remagnetizations

Abstract

Remagnetizations are common in intraplate basins. When remagnetizations occur at an intermediate stage between different tectonic processes, they can be used for paleo-geometrical reconstructions and relative dating of different structures. This has a particular interest in geological frameworks where other geological time markers are absent. In order to apply this methodology, it is necessary to calculate the regional remagnetization direction and subsequently to use this reference direction to restore the attitude of the beds at the moment of remagnetization acquisition. In this work, we use this methodology for dating a pervasive cleavage (whose time of formation is controversial) and the associated structures in the Central High Atlas (Morocco). Paleomagnetic directions from 64 sites were used to calculate the remagnetization direction (D = 330.9°, I = 35.1°, A/n = 6.107) which is coincident with the Albian-Cenomanian (ca. 100 M.a.) expected direction for NW Africa. This direction was used to restore the Mesozoic paleo-geometry of beds allowing us to analyze bedding orientation, cleavage and folding relationships between the present day and the Cretaceous geometry. After restoration we conclude that the development of cleavage post-dates remagnetization, being in relation with Cenozoic basin inversion. However, the paleo-geometry shows incipient folds at Cretaceous times, which can be related to an intra-Mesozoic compressional event.