Deformation structures in Plio- and Pleistocene sediments (NW Bohemia, Central Europe)
Published:January 01, 2003
P. Bankwitz, E. Bankwitz, K. Bräuer, H. Kämpf, M. Störr, 2003. "Deformation structures in Plio- and Pleistocene sediments (NW Bohemia, Central Europe)", Subsurface Sediment Mobilization, P. Van Rensbergen, R. R. Hillis, A. J. Maltman, C. K. Morley
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The small intracratonic Cheb (Eger) Basin in NW Bohemia (Central Europe) is characterized by swarm earthquakes, many mineral springs and mofettes with upper mantle CO2 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.
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Subsurface Sediment Mobilization
Sedimentary facies in the subsurface are usually interpreted from a epositional/stratigraphical perspective: the depositional layering is generally considered to remain undisturbed, except in a few settings. But, there is growing evidence that subsurface sediment mobilization (SSM) is more widespread than previously thought, as new observations arise from the ever-increasing resolution of subsurface data. Many examples are from hydrocarbon provinces but studies elsewhere, for example in preparation for the underground storage of hazardous waste, have yielded unexpected examples. Although until now the different aspects of SSM, including soft sediment deformations, sand injections, shale diapirs, mud volcanoes, etc, have been separated, the new discoveries emphasize their inter-connection, regardless of scale, depth, location, grain size or trigger mechanism. This volume integrates the different aspects of sediment mobilization in the subsurface and their structural consequences, allowing a more generaland a more coherent view of the subject.