Swelling and flow of expanding clays as a cause for non‐tectonic deformations in a glacial–interglacial environment: Holy Cross Mountains, Poland

Abstract

Not all deformational structures are tectonic in nature. Those that do not form under the influence of endogenic causes, but are the result of, for example, gravity, compaction or diapiric extrusion, are referred to as non‐tectonic phenomena. An example of such deformation is the steep and overturned dips of Callovian and Oxfordian layers in the gently folded Mesozoic cover of the Holy Cross Mountains. Their steepening was a result of processes taking place in the underlying ductile formations of Keuper–Rhaetian (Upper Triassic) and Bathonian, slightly enhanced by glaciotectonics. The latter are dominated by claystones, with a minor share of mudstones and sandstones. Their plasticity was due to a significant share of mixed‐layer minerals of smectite‐illite type, which under conditions of high water could swell. Low‐density water‐saturated clays were extruded from under the edge of a limestone slab leading to its deformation. The diapiric flow of the clay‐mass was stimulated by low temperature, high water saturation of rocks and mechanical disintegration associated with freeze–thaw processes during the Pleistocene.