Palinspastic restorations using interfolding remagnetizations. The case of the Cretaceous widespread remagnetization of the Central High Atlas (Morocco)

The Jurassic carbonates of the Central High Atlas (CHA) are affected by a widespread and homogeneous chemical remagnetization. This is an interfolding remagnetization (dated in ca. 100 Ma by comparison with the GAPWP of the African plate) that separates two deformational events; the first one is related to the basinal period in the Atlas (Triassic and Jurassic times) that is responsible of the thick Jurassic sequence that crops out in the CHA. The second one is associated with the tectonic inversion during the Cenozoic caused by the African and European plates convergence, which resulted in the uplift of the cordillera.

Using the Small Circle tools, it is possible (i) to obtain the remagnetization direction and then (ii) use it as reference to obtain the paleodips of each site (i.e. the paleodips at the remagnetization time). This methodology applied to interfolding remagnetizations allows restoring the present-day geometry to the one at ca. 100 Ma and therefore separating the structure associated to the extensional and compressional periods.

This work is framed on an ambitious research project (CGL2016-77560-C2-P, Spanish Ministry of Science and Innovation) in which 700 AMS/paleomagnetic sites and additional 1000 bedding data are integrated to unravel the Mesozoic and subsequent Cenozoic evolution of the CHA. Based on the aforementioned datasets, field work, geophysical (gravimetric and magnetic surveys) constraints and the construction and restoration (at the remagnetization time) of cross-sections, the ultimate goal of the project is to reconstructed and restored the 3-D geometry of the CHA fold-and-thrust belt.  

Here in particular, we present the paleomagnetic data supporting the calculated paleodips. We also analyze how the deformation associated with each of the two deformational events is distributed along the study area. The comparison of dip-domains maps showing the present day attitude and also the pre-inversional one allows analyzing how extensional deformation is more or less associated with particular structures and to understand the importance of the different processes that acted during this period (i.e. deformation associated with extensional faults, salt walls, igneous intrusions, etc.).