Superposed folding resulting from inversion of a synrift accommodation zone, Atlas Mountains, Morocco

Abstract

The conspicuous offset of the northern margin of the High Atlas Mountains is composed of several large superposed folds, one of which is known as the Ait Attab Syncline. The original northeast-trending syncline (F1) was folded by a second set of fold axes (F2) that trend to the northwest. The superposed folding was generated by one phase of compression, with thrusting of synrift rocks northwestward over a prior accommodation zone formed during rifting. This accommodation zone is expressed in the exposure of synrift rocks, the exposure of Paleozoic strata in the footwall, and a coincident offset of topography. Inversion was accomplished by the transport of synrift strata along reactivated normal faults and newly formed thrusts. The unique pattern of refolding is believed to be characteristic of inversion.