| Summary: | Closed depressions in Central Poland are different origin. Two main groups are anthropogenic and natural forms. Many genetic types of the latter can be indentified, e.g.: l. blow-outs accompanying dunes and their complexes; 2. fluvial depressions, e.g. cut-off oxbow lakes at a various stage of decay; 3. karst collapse depressions, both young and largely buried by younger sediments; 4. suffosion steep-walled kettles and gentle hollows; 5. a significant and extensive group of Pleistocene forms in origin of which ice-sheet and permafrost are involved, thus depressions conditioned by: a. irregular glacial accumulation, b. uneven postglaciotectonic surface, c. dead ice melting out, and also from d. degradation of ground ice, e. progressive melting of intrusive ice. The Pleistocene in age depressions commonly occur on till plains and also in the upper sections of dry valleys (Fig. l). Their significance consists, fust of all, in the usefulness of their fillings to palaeogeographical reconstructions. It is the reason for which they were a subject of detailed analyses. Also, an attempt to correlate the results with the existing climatic curves of the Vistulian for Europe and Poland has been made. The interpretation has been based on the studied profiles from closed depressions, supported by palinologic documentation and radiocarbon dates. They are shown in Fig. 2, while the conclusions are presented below. During the Warta ice-sheet recession (150-140 ka BP) the relief of newly deposited tills and of fresh postglaciotectonic surfaces created local base levels in which deposits of wash and solifluction and afterwards mineral-organic sediments accumulated. There processes were retarded somewhat by very poor communities of treeless tundra that changed gradually to a park tundra and a boreal forest corresponding already to the interglacial succession. The Eemian landscape in Central Poland was aboundant in closed depressions. The primary lakes (gyttja, mineral-organic silts) were in the middle and upper Eem transformed into ...
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