Morphology and microstructures of hydroplastic slickensides in sandstone

Abstract

Summary The High Atlas Mountains (Morocco) provide local basins with good Triassic exposures. Basin formation was induced by normal and strike-slip synsedimentary faults, either sealed by Mesozoic and Cenozoic rocks, or reactivated during Alpine orogeny. Thus the Triassic outcrops in these fault zones show not only slickensides obviously due to rupture and friction mechanisms in brittle material (reverse and strike-slip faulting during Alpine orogeny), but also ‘hydroplastic’ slickensides due to faulting in incompletely lithified sediments (normal and strike-slip faulting during Mesozoic pull-apart basin formation). Microstructural and morphological comparison between these two types of slickensides enable us to describe various specific criteria for ‘hydroplastic slickensides’.