Abstrakt
Three new early Miocene fossiliferous horizons were found in the Libouš Mine near Chomutov in the Most Basin. The Libkovice Member of the Most Formation was originally considered as devoid of fossils, apart from rare findings in drillcores.
The new fossiliferous horizons within lacustrine clay sediments can be precisely dated (17.0-17.3 Ma) thanks to their position close to the phosphate-bearing horizons C1-C3 (Fig. 2,3), which allow a broad correlation across the Most Basin (Fig. 1). Newly recognized floras are characterized by common early Miocene representatives of Betulaceae, Myricaceae, Ulmaceae, Aceraceae, Rhamnaceae, Cupresaceae and Pinaceae known from the Most Basin, with possible indication of a warming trend towards the upper fossiliferous/crandallite horizon documented by the presence of thermophilic elements such as Cedrelospermum sp., Bumelia oreadum and Leguminosae gen. et. sp. indet (Fig. 4).
This possible warming trend in the upper part of the Libkovice Member represents the beginning of the Middle Miocene Climatic Optimum, which was confirmed by previous researches. The vegetation analysis distinguished several plant assemblages of azonal riparian forest, mixed swamp forest, and zonal mesophytic evergreen broad-leaved forest mixed with pine stands.
The results of the Integrated Plant Record vegetation analysis demonstrate, that the vegetation corresponds to the Mixed Mesophytic Forest vegetation type with a close affinity to the living plant assemblage of Fagus crenata growing on Mt. Fuji in Japan.