MINERALOGY AND ABRASION OF SAND GRAINS DUE TO VISTULIAN (LATE PLEISTOCENE) AEOLIAN PROCESSES IN CENTRAL POLAND

The Eemian and Vistulian (= Weichselian) sedimentary fill of a closed depression and the glacigenic Saalian substratum at Kalinko as well as the Late Vistulian (= Late Glacial) dune deposits at Zamety were stud ied as representative periglacial sequences for central Poland. Heavy minerals and feldspars were examined by optical methods and by colorat ion with cobalt nitrite of sodium. Quartz grain abrasion was investiga ted by applying a modified Cailleux morphoscopic method and Krygowski' s mechanical graniformametry. Mineralogical changes, especially a decr ease in frequency of amphiboles and an increase of garnets, along with an increase of wind-abraded elements, suggest that these changes have an aeolian origin. The frequency of features which are due to aeolian activity increases progressively in Early Vistulian and Plenivistulia n lake and slope deposits. The degree of transformation is highest in the sands with gravels deposited by slopewash waters and in the sands filling the Late Plenivistulian frost wedges. The degree of transforma tion increases markedly from about 30 000 BP onward and reaches a maxi mum between 20 000 and 14 000 BP, The Late Vistulian coversands and du nes consist of material that was formerly strongly transformed by wind . They do not contain more wind-abraded grains than the Late Plenivist ulian non-aeolian deposits.