Paleogene-Neogene evolution of the central-western Rif fold-and-thrust belt (Northern Morocco) by means of thermal modeling

The Rif belt (Northern Morocco) represents the western termination of the Maghrebides system. It is subdivided into three tectono-stratigraphic domains known as: Internal domain (i.e., Alboran domain), the Maghrebian flysch domain (i.e., the sedimentary cover of the Maghrebian Tethys) and the external domain (i.e., north African passive paleo-margin and its sedimentary infill. The Rif fold-and-thrust belt derives from the deformation of the North African passive Paleo-margin and its sedimentary infill since the onset of Africa-Eurasia convergence. The compressional setting led to the progressive closure of the Maghrebian Tethys and westward translation of the Alboran Domain and its docking onto the Northwest African rifted margin during the Late Burdigalian. However, field structural survey revealed the presence of an important Paleogene unconformity in the External domain, attesting for a deformation older than the Miocene Alpine compression.

Thus, to unravel the Cenozoic history of the Rif fold-and-thrust belt and its burial paths, a regional transect NE-SW-oriented crossing the Rif fold-and-thrust belt is studied. The methodological approach consists in combining organic petrography, micro-Raman spectroscopy on organic matter, clay mineralogy and 1D thermal modelling, together with field structural data.

A new paleo-thermal data set of vitrinite reflectance (Ro%), Raman micro-spectroscopy and %I in I/S mixed layers has been provided. The obtained results show a thermal jump between the Miocene deposits in the Mesorif (External Domain) and their Eocene substratum. In order to fit the paleo-thermal data, the thermal modelling indicates the erosion of about 1300-1900 m of sedimentary and/or tectonic pile before the deposition of Lower Miocene siliciclastic. The obtained results have been used to highlight a disregarded tectonic event affecting the north African paleo-margin and how it is influencing the Miocene orogenic processes.