Plejstocen środkowy w strefie doliny górnej Odry: Brama Morawska-Kotlina Raciborska (próba syntezy)

Abstract

MIDDLE PLEISTOCENE IN THE UPSTREAM ODRA VALLEY REGION: MORAVIAN GATE-RACIBÓRZ BASIN (SYNTHETICAL APPROACH) Summary Previous opinions on age and origin of Quaternary sediments in the Moravian Gate and Ostrava Region are considerably varying from a model of geologic structure of the Quaternary complex in the neighboring Racibórz Basin. Differences are due to opposite neotectonic movements (uplifting in the Moravian Gate and subsidence in the Racibórz Basin) and ice sheet extents during successive Scandinavian glaciations. Fluvial sediments of the widely understood Mazovian Interglacial (Holstein, Mindel/Riss) and palynologic sites of this age lake sediments at Stanova and Gościęcin form the key stratigraphic horizon for the Middle Pleistocene valley deposits of the Upper Odra. Alluvial complex of "the main terrace" limited at the bottom by the soil "Otice" and from the top by the soil "Jaktar" was formed, together with corresponding fossil fluvial series of the Racibórz Basin, during two erosive-depositional cycles that possibly reflect climatic variation of separate glaciations. An analysis of existing materials indicates that the Moravian Gate and adjacent areas of Ostrava and Opava were three times occupied by the Scandinavian ice sheet: twice during the South Polish glaciations ("Elstera complex", Mindel) and once during the Middle Polish glaciations ("Saale complex", Riss). Tills of "the Opava Glaciation" as well as the ones connected with "the Kravare Glaciation" are according to the author older than the alluvial complex of "the main terrace". On the other h and tills of "the Saale complex" occur only within and in the background of "the Hlucina push moraines", the northern rampart of which delimits the maximum extent of the ice sheet of the Odra Glaciation (Oldrisov). To the south of Ostrawa sediments of this glaciation are developed in the extraglacial (alluvial, prolluvial, glaciolimnic and partly glaciofluvial) facies. Only such stratigraphic-genetic interpretation of Pleistocene sediments of the Moravian Gate and the Ostrava Region agrees entirely with geologic structure of the Quaternary complex in the Racibórz Basin. The Warta Glaciation (Riss II) in the Upper Odra valley is represented by sediments of the Muglinov terrace, connected with "the Kravafe Glaciation" (Mindel II). This terrace corresponds with the terrace IV (Ocice terrace) in the Racibórz Basin. The latter is proved by geologic setting and palynologic description of peats from the sites Muglinov and Skrecon as well as by the Lower Paleolithic (Acheulean) site at Racibórz Studzienna and the loess section at Ocice. Lower Pleistocene terraces of the Upper Odra valley and loessy cover of the described area represent the Vistula Glaciation (Wurm).