Climatostratigraphy of interglacials in Poland: Middle and Upper Pleistocene lower boundaries from a Polish perspective

The Brunhes/Matuyama paleomagnetic boundary has been identified in some key interglacial sites in Poland, helping in interpret the results of many years' climatostratigraphic research. The major qualitative stratigraphic boundary is located at the onset of the Mazovian Interglacial (Holsteinian) that separates the older composite from the younger simple interglacials. The two composite interglacials comprise 2–3 interglacial-rank warmings each, separated by profound but non-glacial coolings. The four simple interglacials (Mazovian Interglacial included) are expressed by single warmings only. Each interglacial possesses a characteristic pollen succession, and the successive interglacials are interbedded with tills of the Scandinavian provenance. Simple interglacials are typical of MIS 11-1 and reflect a climate system predominated by 100 ka orbital cycles. Composite interglacials are characteristic of the interval MIS 22-12 and reflect a transition from a climate system predominated by 41 ka orbital cycles to 100 ka cycles, i.e. the mid Pleistocene revolution. Based on these general differences, the MIS 23/22 and MIS 12/11 boundaries are recommended as key thresholds during the Pleistocene and could be reconsidered as the lower boundaries of Middle and Upper Pleistocene, respectively.