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Vistula ralley between the outlets of Dunajec and Breń

xizontaiły laminated. The sand fraction (40—90%) dominates in the grain size composition. The mean diameters are —0.9 to 2.0 0 (0.86— 0.13 mm) provided poor sorting usually.

The variability of the petrographic composition of the gravel fraction reflecting the role of the supply areas of the Yistula catchment is very interesting. The dominating components are sandstones originating of the flysch Carpathians and their amount is rather constant being of ca. 35—45% (Fig. 8 — Wójcina). There is also a fairly large percentage of flintstones and silificated limestones originating of the Jurassic and Cretaceous rock outcrops of the Wyżyna Krakowska (Cracow Upland), Niecka Miechowska (Miechów Basin) and the fringe of Góry Świętokrzyskie (Holly Cross Mts). Their amount increases definitely in the coarsest fractions. The Tatric materiał, represented by granites and ąuartzites, can constitute a few per cent. The northem materiał (granito-ides, metamorphic and effusive rocks), and Carpathian hornstones and lithides as well as the quartzites originating presumably from the Paleo-zoic socle of the Góry Świętokrzyskie Mts are in similar amounts. Quartz, undoubtedly of various origins, is present in several to over 70°/o and its amount increases in the finer fractions.

OVERFLOOD TERRACE

The overflood terrace is built of sediments of the channel, overbank and abandoned channel facies. The former ones are sands and sands with gravels of variable thickness. The profiles of drillings indicate that their thickness does not exceed 4 m in the area of Szczucin where the Miocene clays (Fig. 9) are present directly in the substratum. They over-lie the elder sandy-gravel deposits of the northern trough on the left ri-ver bank. The channel deposits mainly representing the point bar deposits exhibit a poor horizontal lamination usually. The sandy inter-calations, sometimes silty-sand ones, appear between the sandy-gravel deposits and are diagonally laminated. Mean grain diameters were most often from —0.9 to 2.1 0 (1.86—0.23 mm) provided a poor. sorting.

There is a some differentiation in a petrographic composition of the gravel fraction most pronounced in the coarsest, studied here, fraction of 16—32 mm. Gravels of the northem part of the valley (Fig. 8 — Słupiec 3) contain morę flintstones in that fraction and less igneous and metamorphic rocks when compared to those of the Southern part (Fig. 8 — /Słupiec 22). Although two studied sites are located not far one from the other the differences are ąuite significant and denote that mi-xing and uniformity of the petrographic composition are lacking.

The flood deposits — madas •— occur as a compact and almost con-tinuous cover above the channel deposits. Their thickness is 1—5 m, and most freąuently 1.5—2.5 m. Some of their vertical profiles are definitely