Lower Permian sediments of the Intrasudetic Basin: a record of cyclic, climatically-controlled transitions from lacustrine to terrestrial conditions

The geology of the Intrasudetic Basin (Poland and Czech Republic) in the past was studied separately in both countries. Our project combined data from both parts of the basin to study the development of the limnic basin during the seasonally extreme climate in the Early Permian. The Lower Rotliegend Słupiec Formation (Broumov Formation in the Czech part) red bed deposits appear the most promising for palaeoenvironmental and palaeoclimatic studies. Fine-grained weathering products  (black shales), tuff admixtures and autochthonous components (limestones) in lakes contain many remains of plants, and traces of activity of invertebrates and vertebrates including extraordinarily numerous traces fossils of tetrapods (reptiles and amphibians) (e.g., Voigt et al. 2012) and fish remains (e.g., Stamberg & Zajíc, 2008). The Słupiec Formation is interpreted as a successively finning-upwards megacyclothem consisting, from base to top, of alluvial fan, fluvial and lacustrine deposits (Wojewoda and Mastalerz, 1989; Kurowski, 2004). However, the cyclicity is also clearly marked by successive transitions from lacustrine sediments with preserved fish remains to terrestrial sediments with numerous tracks of terrestrial reptiles and amphibians. This seasonal climate with dominant monsoonal rainy summer and winter seasons with low precipitation is clearly recorded in deposits of alluvial-fluvial plains and lakes. Extreme weather conditions, such as possible night frosts, were also recorded in the sediments, although the basin was located relatively close to the equator.

This research was funded by the Polish National Science Centre (Grant 017/26/M/ST10/00646).

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