Deformacje konwolutne w osadach glacjolimnicznych i glacjofluwialnych zlodowacenia Wisły w okolicach Gór zna i Lidzbarka Welskiego

Abstract

CONVOLUTION DEFORMATIONS IN GLACIOLIMNIC AND GLACIOFLUVIAL DEPOSITS OF THE WISŁA GLACIATION NEAR GÓRZNA AND LIDZBARK WELSKI Summary Glaciolimnic and glaciofluvial sediments of the Vistula Glaciation age near Górzno and Lidzbark Welski contain convolute deformations. Within glaciolimnic sediments to the north of Górzno the convolute structures occur within three beds and form diapir-like ridges or narrow folds and microfolds with amplitude from several to several dozen contimeters. Development of these deformations started after deposition due to vertical movements of fresh sediments with unstable density bedding. Convolute deformations noted in glaciofluvial sediments to the south of Lidzbark Welski, form distinct folds with amplitudes of 10-12 cm, inclined upcurrent and locally erosively cut in the top. These convolutions are of synsedimentary origin and developed due to friction of turbulent current passing over a non-consolidated and water-saturated sand with ripplemark small-scale bedding at varying pressure. They could be formed at simultaneous passing of water through a loose deposit or extraction of water from the sediment at bottom friction of turbulent current.