Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Geological investigation on the confluence of the Dyje, Kyjovka and Morava rivers

 

Pavel Havlíček, Eva Břízová, Jan Hošek, Tamara Sidorinová

Geoscience Research Reports 49, 2016, pages 225–232
Map sheets: Břeclav (34-23)

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Published online: 30 September 2016

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Abstract

This article is focused on the results we have gathered during the geological mapping of the northern part of the Vienna Basin. We have found fluvial terrace infills of the Morava and the Dyje rivers belong to the middle Pleistocene period with bases in relative altitude above floodplain surface 15-22 m and 0-2 m (so-called the main terrace step). The thickness of the sedimentary infill ranging between 1 to 11 m. The upper parts of the sedimentary infill are often affected by the periglacial processes and covered by aeolian sand from the Last Glacial period. Results of lithological analysis show the dominance of quartz and crystalline rocks. From the analysis of heavy minerals we recognized dominance of amphibole and garnet. The recent floodplains consist mainly of the sand and gravel of the upper Pleistocene age. Their thickness is up to 9 m. We dated the remains of bounds of glacial faunas and trees which indicate peniglacial age (22 400 ± 2 500 years BP, 35 514-19 836 years BC and 16 170 ± 480 years BP, 18 811-1¬6 576 years BC). During the Last Glacial period and the early Holocene the fine-grained fluvial and aeolian deposits of the floodplain infill were affected by resedimentation. It caused the development of sandy elevation with the range 2-6 m maximally 8 m in lenght. We called them "hrúdy". The polygenetic (?) origin of these structures is based on the microtextures on the surface of the quartz grains. This hilly landscape was colonized with short breaks since the mesolithic age up to the Great Moravia period. We suggested multiphases development of the "hrúdy" structures which is supported by the mesolithic artefacts and the buried chernozem soil inside of the sandy infill (Barvínkův hrúd southeast from Břeclav-Pohansko hunting lodge). We recognized many paleochannels with organic-mineral infill which have occurred in the Holocene muddy sandy floodplain infill. Palynological data of humolits and paleochannels infill indicate late Holocene sedimentation. It consists mainly of pollen grains from the bottomland forest (Quercus, Tilia, Fraxinus) and palynomorf synantropic plants, which are typical for colonization age. Furthermore, there is frequent occurrence of pine (Pinus) and sometimes hornbeam (Carpinus) which represented dried places ("hrúdy") in the studied area.