干旱区生态环境知识资源中心

We question for the first time the origin of enigmatic structures, herein termed syncline-topped anticlinal ridges (STARs). In the Central High Atlas (CHA) of Morocco, small synclines of Upper Palaeocene-? Eocene deposits are only preserved on top of Triassic-Jurassic anticlinal ridges. We explain these peculiar structures through a three-step evolution: (i) early halokinetic evolution leading to the formation of elongated diapiric ridges over basement faults, ending with magmatic intrusions and enhanced diapiric ascent up to the surface; (ii) Palaeocene-? Eocene unconformable sedimentation; (iii) Late Eocene-Quaternary shortening phases, which resulted in the erosion of the Palaeocene-? Early Eocene deposits, except in the breached anticlinal axes. The comparison with the breached valley (’makhteshim’) of the Syrian Arc in the Negev Desert allows us to emphasize the role of the early diapiric evolution of the CHA domain in the genesis of the STAR structure.