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3.3. GRAIN SIZE AND SORTING CHARACTERISTICS OF DUNE SAND

The examined Plenivistulian dunes are composed of medium- and fine-grained sand with silty sand interlayers (Fig. 8). They contain morę silt frac-tion, and sand is morę poorly sorted in comparison with the Late Glacial dunes. The values of main granulometric indices (according to Folk and Ward) rangę in the following intervals: Mz = 1.73 - 2.36, a, = 0.60 - 1.64, Sk, = (- 0.03) - 0.55, K_G = 0.80 - 1.69. The lowest values of mean grain size were found in the Żuków dunes, and the highest - in the Kazanów dunes. Most poorly sorted sand occurs in the Uściąż dunes.

It should be noted that the Uściąż dune area adjoins the large loess patch (Lublin Upland), and the Żuków dune area is situated near the loesses of the Roztocze region. These locations could have influenced grain size and sort-ing parameters of the examined dunes.

3.4. DIRECTIONS OF WINDS

The author considers that the Plenivistulian dunes in Poland were formed by WNW winds (281-290°). The WNW-ESE dune ridges indicate this direc-tion of dune-forming winds. Westerly, and not easterly wind direction is ev-idenced by the position of dunes in relation to other relief forms (edges, riv-er valleys), the encroachment of dunes on slopes from the west, and also the position of dunes in relation to their potential alimentation areas. J. Goździk (1991,1995) also postulated the WNW direction of aeolian sand transport in the Upper Plenivistulian (dated by him at 25-14 ka BP) in central Poland.

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Fig. 8. Grain size and sorting parameters of the Plenivistulian dunes (Żuków, Uściąż, Kazanów)

Parametry uziamienia wydm plenivistuliańskich (Żuków, Uściąż, Kazanów)

• Żuków ■ Uściąż O Kazanów