In the middle section, the Warta River valley runs through the Adamów graben. Th e graben was characterized by subsidence since the end of the Paleogene and favoured accumulation during the Neogene and the Quaternary. Th e Quaternary deposits consist of several till horizons separated mainly by a series of fl uvioglacial sand and a thick series of glaciolacustrine sediments. Th e research was concentrated on three upper levels of tills and selected series of sand available in Koźmin and Koźmin-Północ "Adamów" opencast mines. Th e lithological, petrographical features and long-axis azimuth of pebbles were analyzed. Th e results showed that the lower till could be dated to the Elsterian, middle till to the Wartanian, and the upper till is probably also Wartanian. Glaciolacustrine deposits which fi lled the erosional form and appeared in the middle till correlate with the end of the Wartanian.
The complexity of glacial sequences may increase when these formed underneath ice sheets despite subsequent changes in their extent that are accompanied by alterations in the direction of the ice flow. Our aim was to determine whether or not changes in ice sheet dynamics during the Late Weichselian are also recorded in sediments formed north of the area of its fluctuating margin (i.e., where the ice sheet prevailed independent of such fluctuations). It is shown that in these areas such a record could have occurred, as documented by results of till studies at Babie Doły. The examination was carried out using several analyses: lithofacies properties of sediments, petrographic till composition (fine gravel fraction, indicator erratics), till matrix CaCO3content, till fabric, as well as orientation of striae on the top surfaces of large clasts. In parallel, datings of sub- and supra-till sediments using the TL method were carried out. The basal till at Babie Doły represents almost the entire Upper Weichselian, but it can be divided into subunits whose features indicate different ice flow directions and debris supply. The lower subunit developed as a result of the palaeo-ice stream along the main axis of the Baltic Sea (from the north), expanding to areas adjacent to the depression of the Gulf of Gdańsk. The upper subunit developed when the influence of the palaeo-ice stream in the study area decreased, the main role having been taken over by the ice flowing from the northwest. The till analysed also shows considerable lateral variation, indicative of the mosaic nature of subglacial sedimentation. We consider the diversity of permeability of deposits over which the ice sheet extended to be the prime factor that determined such a situation.
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