Genesis of transverse kame trains in eastern Poland

Abstract

Transverse kames, forming trains perpendicular to the direction of ice-sheet advance, are rare morphological elements in previously glaciated areas. The genesis of an example from the ice-contact zone of the Wartanian glaciation in eastern Poland is discussed. The transverse kames there form two main, distinctly separated, sub-parallel trains. Their sedimentary successions fill erosional troughs incised in the pre-Wartanian deposits on northern slopes. They consist of thick glaciofluvial sand and glaciofluvial/glaciolacustrine sandy/silty units that are covered with a thin, usually discontinuous, glacial till succession. The genesis of this kame type has been modelled. It is concluded that transverse kames developed in two phases: (1) erosion of the substratum in subglacial channels during initial deglaciation, and (2) glaciofluvial deposition in crevasses during advanced deglaciation (in the form of low-energy fans periodically submerged under stagnant water), followed locally by a cover of flowtills. Both the ablation of the ice and the accumulation of the kame deposits were controlled by the co-occurrence of ice zones either enriched or impoverished with sediment. Zonal enrichment of ice with debris was determined by the development of shear zones over substratum elevations that were inclined up-ice. The formation and subsequent infilling of crevasses both took place in zones of relatively clean ice, so that the resulting kames form a train perpendicular to the direction of ice movement.