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Fig. 5. Cross-sections of the subglacial channels (Niczów in Pomerania Lakeland and Objezieize in Great Poland Lakeland), and Wieprz River valley, north of Lublin (simplified). Cr - Cretaceous, Ol - Oligocene, Mi - Miocene, N+S - Narewian and Sanian cold stages, M -Mazowian, O — Odranian, V — Vistulian, H - Holocene Przekroje subglacjalnych koryt rzecznych (Niczów na Pojezierzu i Objezierze w Wielkopolsce), dolina Wieprza, na północy Lublina (uproszczone). Cr—Kreda, Ol - Oligocen, Mi — Miocen, -fazy Narwi i Sanu, M - mazoweckie, O - odrzańskie, V - wistuliańskie, H - Holocen

In the Warsaw region it is rather impossible that the Mazowian bottom of the Vistula river occured at 30 m a.s.l. (Sarnacka 1982). A better propos-al is a conception (Lindner, Marks 1999), that the Vistula valley bottom occured at that time about 50 m a.s.l. Various proposals were put forward con-cerning the northern part of the Polish Plain. The latest of them has been described by Niewiarowski, Wysota (1996) and Lisicki (1998). The first sug-gestion maybe ruled out, because - 40 m b.s.l. in the vicinities of Lidzbark Warmiński, 100 km far from the Sztum Sea is distinctly too deep! The com-parison between the va!ue of 0-40 m a.s.l. at the Mazurian Lakeland and -20 m for Domnowo marinę beds is much closer, and therefore Lisicki’s (1998) proposal is morę reliable (Fig. 6).

The above, very briefly described example, conceming the Mazowian Vistula valley clearly shows the various difficulties with the palaeomorphic interpretation of interglacial fluvial valleys iii the Polish Plain, and also illus-trate the possible ways of solving them.