Late Eocene landscape, ecosystems and climate in northern Bohemia with particular reference to the locality of Kučlín near Bílina


Authors: Kvaček Z

Published in: Bulletin of Geosciences, volume 77, issue 3; pages: 217 - 236; Received 18 December 2001; Accepted in revised form 15 April 2002;

Keywords: Late Eocene, landscape, ecosystems, northern Bohemia, volcanic complex,

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A new interpretation of the Late Eocene landscape in northern Bohemia is offered. Late Eocene age has been proven by palaeontological records and radiometric dating of volcanogenic strata representing the earliest surface products of volcanic activity in the České středohoří Mountains (the lowermost part of the Středohoří Complex, Ústí Formation p.p.). Most of them, the sites of Kučlín, Kostomlaty - Mrtvý vrch and Roudný, and the lower parts of the sections at Lbín (core Lb 1), Hlinná (core Úc 9), and Kundratice (core KU 1) line the southern periphery from Bílina to Litoměřice. These deposits, which comprise diatomites, marlstones to limestones, tuffitic claystones or coarser volcaniclastics, represent a volcanic facies coeval with the Staré Sedlo Formation, which is composed of quartzites, sandstones and sands of fluvial settings. Although the floras of either lithostratigraphic unit differ in some respect, this is due to the synecology of vegetation and environmental differences (aquatic to upland communities on fertile volcanogenic soils versus riparian forests along rivers on oligotrophic sandy soils). A volcanogenic lake system apparently existed in the southern part of the České středohoří Mountains at that time, which was drained across northern Bohemia and Saxony towards the North Sea, as corroborated by fish fauna (Morone). The Kučlín diatomite and the other mentioned sites at the base of the Ústí Fm. reveal mainly a mesophytic forest vegetation suggesting a warm, (paratropical) subtropical seasonal climate without frosts and with slightly deficient (? summer) precipitation. Plant assemblages of the Staré Sedlo Fm. reflect azonal, predominantly woody vegetation along riverbanks (riverine gallery forests). This type of vegetation, supplied by groundwater, was also (paratropical) subtropical and seasonal but perhumid in aspect. Such differences between plant assemblages connected with the basinal/fluvial versus volcanogenic environment can be found elsewhere during the Paleogene (the Middle Eocene sites of Messel, Eckfeld and Geiseltal or the Early Oligocene sites of the České středohoří Mountains and the Haselbach Floral Assemblage in Saxony). At Kučlín and the other listed localities of the earliest effusive activity, no distinct hiatus (sedimentation gap) towards the Staré Sedlo Formation existed. The Late Eocene landscape of northern Bohemia, in contrast to the hitherto accepted interpretation, was a peneplain with lowland rivers, lakes, maars and moderate volcanic uplands.