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However, this paper does not concem the Late Vistu I ian dunes because    nl

thcy havc been sufficicntly rccognizcd. A ąuestion under discussion is the    /q

occurrence of older dunes in Poland, i.e. those of the Plenivistulian age.    _nj

The author has succeeded in discovering and evidencing the occurrence of the Plenivistulian dunes visible in modem relief. This fact throws new light    p]

on the problem of the number of dune-forming phases. The results of a research    A

on these dunes provide some new information on the Plenivistulian palaeo-    A

geographical conditions, and especially on the prevailing wind directions.    J

o

2. PROBLEM OF THE PLENIVISTULIAN DUNES IN THE LIGHT    o

OF LITERATURĘ    (

tj

Aeolian processes were very important in periglacial zonę during the

Plenivistulian when climate was cold and dry. Strong winds caused deflation and corrasion; ventifacts and windpolished boulders were formed, and aeolian deposits (loesses, aeolian coversands, fluvio-aeolian sands) accumulat-ed. In Europę these phenomena were described in many papers (Bose 1991; Christiansen, Swensson 1998; Goździk 1991; Kasse 1999; KozarskL Nowaczyk 1991; Liedtke 1993; Lindner 1971,1972,1976; Maruszczak 1967,1968, 1983 Schirmer 1999; van Huissteden et al. 2001). A ąuestion can be put about dunes. Whether they were not formed during the Plenivistulian or they were destroyed as so little information about them is available? And if they were formed, whether they have survived to the present?

Inland dunes occurring in Georgia and Louisiana (southem part of the United States, North America) originated in the peripheries of periglacial zonę of the Wisconsin Glaciation. They were TL dated at several phases of the last glaciation, and mainly at the Upper Pleniglacial, i.e. 30-15 ka BP. These dunes were formed in cold and dry climate (Ivester et al. 2001; Otvos, Price 2001).

In West Europę the Plenivistulian dunes were found only in the Nether-lands (van Huissteden et al. 2001). These dunes are Iow, rather fiat ridges.

S.Z. Różycki (1967) was the first who noticed the occurrence of the Plenivistulian dunes in Poland. He considered the Late Glacial Systems of parabolic dunes to be accumulated in one of the last stages of dune forma-tion. In his opinion the dune ridges several metres high, which show a W-E orientation and occur in Błonie Plain (central Poland) are the oldest presen ed dune generation. He thought that these dunes dated from the Leszno (Bran-denburgian) Stadial of the last glaciation so they should be older than 20 ka BP. The subseąuent studies indicated that these ridges having a generał WNW-ESE orientation consist of fiat and irregular sandy hummocks. The TL age