Surface microtextures of quartz grains from Vistulian loesses from selected profiles of Poland and some other countries

摘要

The Vistula Glaciation loesses have been investigated in comparison to some profiles from Central Europe. On the basis of quartz grains examination in SEM and referring to lithological features, a reconstruction of the sedimentary environment and transport type is made. Analysis of frequency of quartz grains with definite features shows important variations (in terms of type and quantity) amongst the features. The most varied microtexcures are observed on 1.0-0.5 mm grains and smaller—0.5-0.25 mm. Completely different microtextures have been recognized on 0.1-0.5 mm grains, on which encrusted smooth surface formed due to precipitation of silica at deflation sites, can be observed. The 0.1-0.05 mm quartz grains from the Polish loesses indicate one source area with an arid climate. The grains were probably transported by high winds from a distant area located in the East. In contrast, the coarser (sand-sized) quartz grains indicate a variable provenance. They usually originated from an adjacent area and underwent limited transport. A distinct difference in microtextures of quartz grains occurs at the boundary of the younger middle loess (LMs) and younger upper loess (LMg). LMg is best defined by more aeolian and fewer corrosional post-sedimentary features.