Oblique extension in the Jurassic trough of the central and eastern High Atlas (Morocco)

Abstract

A field structural analysis has been carried out in the High Atlas Mountains of Morocco. Paleostress solutions provide information on the successive orientations of major stress patterns during Mesozoic and Cenozoic time. An initial rift stage in the Early Jurassic is characterized by normal–oblique faults bounding tilted blocks, which are associated with tensional paleostress patterns whose minimum component trends west-northwest–east-southeast. Faults parallel to this direction are interpreted as paleotransfer faults. We assume that the divergent motion responsible for the opening of the rift system in the Early Jurassic was oriented west-northwest–east-southeast, subparallel to the paleotransfer faults and the trend of the minimum component (σ3) of the paleostress field. The east–west-trending Jurassic central–eastern High Atlas rift opened obliquely, and not in a pure strike-slip stress regime along east–west-striking faults as previously proposed. A later stage of rifting (Middle Jurassic) is characterized by large normal faults and is supposed to accompany local movements, probably due to gravity. The uplift of the High Atlas belt occurred mainly during the Cenozoic period as a consequence of a north–south- to northwest–southeast-directed compression related to collision between Europe and Africa.