Morphostratigraphical correlation of river terraces in the central part of the Bohemian Massif with the European stratigraphical classification of the Quaternary
Abstrakt
The results of geomorphological research, focused on identification of larger remains of fluvial terrace sedimentary sequences in the Želivka, Sázava, Berounka, Vltava and Labe river-drainage basins in the Bohemian Massif, are presented. The terrace flights are characterised by a variable structure which is conditioned by the bedrock and drainage-network configuration created prior to the Pleistocene.
They are formed by the specific hydrodynamic processes during the Quaternary. A series of transverse-valley profiles and longitudinal profiles have been constructed.
This has enabled the differentiation of seven main terrace surfaces underlain by Quaternary fluvial sediments. However, the uppermost levels are underlain by Neogene-age deposits that comprise both fluvial and fluvio-lacustrine sediments at altitudes up to 135 m above the present valley floor.
The Quaternary incision of the Sázava and Vltava valleys reaches an average depth of over 100 m. This was induced by neotectonic uplift of the Bohemian Massif.
The terrace flights include incised meanders and bends, most of which formed during the Middle Pleistocene. Based on the currently accepted Quaternary chronostratigraphical scheme, the terrace system throughout the Bohemian Massif is mostly of Middle and Late Pleistocene age that is the period from the Cromerian Complex to the Weichselian stages of the NW European scheme.
A marked erosional episode, that pre-dates the accumulation of terrace I sediments, occurred at the end of the Early Pleistocene Subseries. Older levels of fluvial sediments in the central part of the Bohemian Massif, occupying higher topographical positions, previously classified as of Pliocene age, are now considered to date from the Early Pleistocene.