Late Saalian (Wartanian) glacial palaeogeography and formation of end moraines at the northern slope of Silesian Rampart, Southwestern Poland
Abstract
Paleogeografia zlodowacenia Warty i powstanie moren czołowych na północnych stokach wału śląskiego, południowo-zachodnia Polska
There is evidence, hitherto often denied, for the ice marginal features, including the end moraine hills along the Silesian Rampart, SW Poland. These end moraines are attributed to the regional advance o f the Wartanian ice sheet into its maximum position, which is also marked by subglacial till bed. The end moraine hills are located on the northern slopes o f the Silesian Rampart and they are very rare, partly due to subsequent erosion, but mainly due to conditions not favourable for a remarkable proglacial accumulation. The Wartanian end moraines of southwestern Poland possess several features that suggest that they are end moraines with dominant waterlain, stratified sediments. They are interpreted as alluvial fans, where the ice margin is represented by a ‘scarp’. They have semi-conical form, often plano-convex geometry and an average distal slope o f 2-25°. These fans are equivalent to sheetflow-dominated or ‘humid’ alluvial fans in non-glacial environments. Sedimentary sequences of the end moraines consist mainly o f coarse-grained material, with boulders up to 1.8 m in diameter, with typical sediments o f ‘proximal fan’ with a highly pulsatory water discharge. The formation o f the end moraine followed the formation o f a proglacial lake and strong erosion after its drainage. The end moraine was formed during oscillation o f the ice margin that resulted in local glaciotectonic deformation o f the end moraine fan sediments (push) and a set of parallel hills, with successive younger alluvial fans (retreat).
There is evidence, hitherto often denied, for the ice marginal features, including the end moraine hills along the Silesian Rampart, SW Poland. These end moraines are attributed to the regional advance o f the Wartanian ice sheet into its maximum position, which is also marked by subglacial till bed. The end moraine hills are located on the northern slopes o f the Silesian Rampart and they are very rare, partly due to subsequent erosion, but mainly due to conditions not favourable for a remarkable proglacial accumulation. The Wartanian end moraines of southwestern Poland possess several features that suggest that they are end moraines with dominant waterlain, stratified sediments. They are interpreted as alluvial fans, where the ice margin is represented by a ‘scarp’. They have semi-conical form, often plano-convex geometry and an average distal slope o f 2-25°. These fans are equivalent to sheetflow-dominated or ‘humid’ alluvial fans in non-glacial environments. Sedimentary sequences of the end moraines consist mainly o f coarse-grained material, with boulders up to 1.8 m in diameter, with typical sediments o f ‘proximal fan’ with a highly pulsatory water discharge. The formation o f the end moraine followed the formation o f a proglacial lake and strong erosion after its drainage. The end moraine was formed during oscillation o f the ice margin that resulted in local glaciotectonic deformation o f the end moraine fan sediments (push) and a set of parallel hills, with successive younger alluvial fans (retreat).