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ments has been accumulated at a period prior to the last ice-advance in the area under investigation.

Kępa Strzemięcińska. A generał scheme of its geological structure is presented in fig. 4. It is built of lower litho-stratigraphic horizons of the Baltic glaciation: of the key intra-till horizon consisting of fine-grained sands and grey varved clays together with the third till strata plus glacial and fluvioglacial depos-its accumulated by the penultimate in the investigated area Scandinavian ice-sheet. Facial character of the last-named deposits and their modę of occurrence in the fossil moulding of the glacial bedrock at Rządz (fig. 31) provides further evidence in support of areał decay of the ice-sheet. Beneath the erosional surface of the river terrace lying at a level of about 33 m a.s.l. are exposed deposits that, gene-rally speaking, can be divided into two groups: the first, comprising deposits lying in situ of series A (phot. 10, fig. 31 — 14-9): and the second, comprising redeposit-ed deposits of series B_% C, D and E (phot. 10, fig. 31 — 1-8). Deposits from the second group fili up the fossil hollow carved in the bed of the crevasse by melt--waters. The modę of occurrence and textural features of series C and D (phot. 11) point to their accumulation to have taken place in intraglacial or superglacial conditions, and that they were later gravitationallv replaced in frozen state down a crevasse slope. The E series deposits (phot. 12) represent the finał phase of infilling of the erosional fossil form. Considerable ąuantinties of relatively well--preserved fossil mollusk shells and their fragments were found in them.

Results of the above-presented analyses allowed for drawing the conclusion that decay of the penultimate in the area under investigation ice-sheet involved three stages conditioned by successive changes in the climate: from the warming phase through the cooling phase back to the renewed warming phase. Individual stages of the deglaciation left their marks on deposits and forms varying as to the genesis. The first deglaciation stage is characterized by subglacial till and by the bulk of superglacial subaquatic till. The second stage, when the ratę of melting was slackened, is represented principally by superglacial-solifluction till. The till occurs at those places only where the relief of decaying icersheet was varied and not covered with a layer of water at the time when the deposit was forming; whereas the third deglaciation stage has been marked by fluvioglacial sediments and gravitationally replaced intra- and superglacial deposits filling the hollow forms carved by melt-water in the floor of crevasses and free spaces be-tween blocks of dead ice. It is only in these deposits that the remnants of mam-mal and mollusk fossil fauna was met with. It was probably not until the last deglaciation stage that inglacial till melted of from the ice.

Taking into account this three-stage, climate-conditioned process of areał deglaciation, as well as the fact that the last two Scandinavian ice-sheets in the area under consideration had separate alimentation areas, which separateness is indicated by discovered differences in the petrographic composition of gravels and till-fabric between lodgment tills of the first and second till strata, the author relates to the same period the penultimate deglaciation time within the Grudziądz Basin and the tripartite Paudorf Interstadial (Inerpleniglacial according to Van Der T. Hammen, G. C. Maarleveld, J. C. Vogel, W. H. Zagwijn 1967). In con-sequence, the author assumes that the lower part of the Baltic-glaciation stratig-raphic profile (fig. 40) with two till strata and fluvioglacial sediments separating them, with a total thickness of about 60 m, was deposited in the period from the Eem Interglacial up to the Paudorf Interstadial inclusive (a lapse of time of about 40 000 years), while the upper part, which includes one till strata and locally