Seismic shocks, periglacial conditions and glaciotectonics as causes of the deformation of a Pleistocene meandering river succession in central Lithuania

Małgorzata Pisarska-Jamroży, Szymon Belzyt, Albertas Bitinas, Asta Jusienė, Barbara Woronko
Abstract. An extraordinary variation of plastic and brittle deformation structures with periglacial, glaciotectonic and seismic features was observed within the unconsolidated, upper Pleistocene meandering river succession in the Slinkis outcrop in central Lithuania. Among these deformations, the following structures were described: (1) ice-wedge casts in the lower part of the sedimentary succession, linked to periglacial processes, (2) soft-sediment deformation structures, such as load structures (load casts, pseudonodules), flame structures and water/sediment-escape structures, all trapped in clearly defined layers in the upper part of the sedimentary succession, which are related to the propagation of seismic waves, and (3) faults occurring throughout the sedimentary succession, which are associated with glaciotectonic processes. To our knowledge, this is the first description and analysis of the combined presence of such a diverse range of deformation features caused by three trigger mechanisms in a meandering fluvial sedimentary succession.
Keywords: soft-sediment deformation structures; brittle deformations; seismite; periglacial features; glaciotectonic deformations; liquefaction; meandering river deposits