Abstrakt
Pronounced climatic warming associated with the Late Weichselian Pleniglacial-to-Lateglacial transition caused considerable environmental changes throughout the former periglacial zones (in Europe ~53°-46°N). During permafrost degradation and subsequent ground subsidence (i.e. thermokarst processes), the landscape changed rapidly.
In this study we investigated a flat mid-altitude area in south Bohemia, Czech Republic, lying close to the southern limit of the Weichselian permafrost. We discovered palaeo-lake basins with sedimentary infillings up to 11 m in depth.
According to radiocarbon and palynostratigraphical dating, these basins were formed at the onset of the Late Pleniglacial-to-Lateglacial transition, whereas the smaller depressions were formed later. We suggest that the basins resulted from thermal and fluvio-thermal erosion of the former permafrost and represent remnants of discontinuous gullies and possibly collapsed frost mounds (pingo/lithalsa scars).
The formation of this a fossil thermokarst landscape was climatically driven and multiple phased, with the major phase during the climatic warming and wetting at the onset of GI-1e (Bolling) and the minor phase during GI-1c (Allerod). This study enhances knowledge of the palaeogeography of the former European periglacial zone by showing that Late Pleistocene thermokarst activity could have had a significant impact on the evolution of the landscape of at least some regions of central Europe along the southern limit of the continuous permafrost zone.
The research also points to a similar history for the physical transformation of the landscape of the former European periglacial zone and current thermokarst landscapes and could be a valuable source of information with respect to the future transformation of the Arctic under conditions of ongoing global warming.