Deformation structures in Plio- and Pleistocene sediments (NW Bohemia, Central Europe)

Abstract

Abstract The small intracratonic Cheb (Eger) Basin in NW Bohemia (Central Europe) is characterized by swarm earthquakes, many mineral springs and mofettes with upper mantle CO 2 degassing and by neotectonic graben and basin structures. Especially in non-lithified Upper Pliocene clay formations of the basin, a variety of deformation patterns is exposed. They include non-tectonic and tectonic activity and comprise faulting and folding from µm- to km-scale. Previously unrecognized N-S- and ENE-striking faults are sites of mantle degassing and seismic activities. Confined-layer deformation and liquefaction structures hint to palaeoseismic events and gas escape activity. Cleavage-like arranged clay mineral plates represent the microfabric of clay within fault zones. For the first time the degassing channels of Upper Mantle fluids/gases through the Pliocene clay sediments can be documented: µm-scale micro-tubes were produced by the opening of Riedel shear planes induced by fault movements.