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Microstructures, subglacial till deposition, and shear band development revealing up-section changes in shear–A study from Weissbach, Austria

2018; Elsevier BV; Volume: 130; Issue: 2 Linguagem: Inglês

10.1016/j.pgeola.2018.11.001

2773-0743

John Menzies, Jürgen M. Reitner,

Pleistocene-Era Hominins and Archaeology

Tills from an exposure in Wildschönau Valley, northern Austria were examined using microsedimentological techniques. The tills exhibit a range of microstructures indicative of soft sediment deformation within temperate subglacial bed conditions. The tills can be subdivided at the macroscale into a lower grey and upper red till both of which exhibit some sedimentological variations; however, at the micro-level the tills appear essentially identical. The microstructures in the tills are illustrative of structures developed during deformation both during and following their emplacement. Of note are the microshears within these tills that are demonstrative of changes in applied stress. Both low ( 25°) microshears were mapped and their fabric data analyzed. The microshears show a change in stress levels ascending through successive till units. The changes in stress are demonstrative of spatially and temporally changing rheological conditions undergone by the subglacial tills during deformation, ongoing deposition/ emplacement and stress localization. These findings indicate that microstructures reveal local deformation conditions in tills and a more detailed micro-history of paleo-stress.