VÝZNAM VALOUNOVÝCH ANALÝZ LEDOVCOVÝCH SEDIMENTŮ PRO PALEOGEOGRAFICKÉ REKONSTRUKCE PLEISTOCENNÍHO KONTINENTÁLNÍHO ZALEDNĚNÍ JESENICKA

• Published in: Geologické výzkumy na Moravě a ve Slezsku
• Main Author: Hanáček, Martin
• Format: Article in Journal/Newspaper
• Language: Czech
• Published: Masaryk University 2014
• Subjects: clast petrology and provenance; continental glaciation sediments; advance directions of continental glacier; Pleistocene; Nisa; Ice Sheet
• Online Access: https://journals.muni.cz/gvms/article/view/2739

Sediments of Middle Pleistocene continental glaciation at the northern foothill of Rychleby Mts. and Zlaté Hory Highland contain clasts of local to Nordic provenance. Local clasts originating from crystalline units of the above-mentioned mountains prevail. These clasts have palaeogeographical importance for a local reconstruction of ice sheet advance directions. General advance direction from NW to SE has been reconstructed basing on local clasts in earlier studies (mainly Gába 1981a, b; Gába – Pek 1999). This interpretation has been based on the fact that the shares of clasts of rocks cropping primarily in NW part of the Rychleby Mts. decrease towards the SE. New, in this contribution presented, interpretation reconstructs the ice sheet advance generally from the North to the South, with variations conditioned by local landscape. Glacial sediments have at each site in the NW–SE direction petrological composition, which corresponds to the lithology of a mountain part south of the site of concern. Gierałtow orthogneiss clasts predominate in glacial deposits of the NW part of the main ridge forefield of Rychleby Mts. The share of amphibolites rises significantly in the forefield of the central part of the Rychleby Mts. main ridge. Feldspar and muscovite quartzites dominate in the area of Sokol Ridge and Zlaté Hory Highlands. The new interpretation presumes the colluvial, alluvial and fluvial transport of the debris towards the northern and north-eastern mountain forefi eld before the ice sheet advance. Ice sheet advancing from the North eroded and transported this debris towards the South. Preglacial sediments corresponded petrologically to the mountain parts, from which they originated. Thus, glacial sediments have petrological composition, which corresponds to the lithology of those mountain parts, which lies south of the sediment occurrence. Part of the debris has been transported by Nisa Kłodzka River from the West towards the East already before the glaciation.The following pattern could be found in the ...