Aeolisation of sandy deposits in the Bór Biskupi Basin (eastern part of Silesian Upland – southern Poland)

Jolanta Pełka-Go�ciniak

University of Silesia, Faculty of Earth Sciences, B�dzi�ska str. 60, 41-200 Sosnowiec, Poland

pelka@us.edu.pl The eastern part of Silesian Upland which directly neighbours with Middle Triassic and Upper Jurassic cuesta is characterised by the large occurrence of sandy deposits. The largest areas and thickness they reach within basins, among others Biskupi Bór and Mitr�ga Basins, which have the character of wide depressions, originated in the Tertiary in result of tectonic movements activity (Pełka-Go�ciniak, 2004).

The genesis of these sands can be determined as complicated, i.e. in different parts of this unit can occur deposits of genesis as follows: fluvioglacial, fluvio-proluvial, fluvial, proluvial-deluvial, and they formation should be mainly connected with the Middle Polish and Vistulian Glaciations (Pełka-Go�ciniak, 2000).

By assessment of shape and surface features of quartz grains it is possible to state a kind of transport, which the grains were undergone. The character of grain abrasion differentiates deposits of diverse origin, history of grains and the character of source material. High degree of abrasion is typical for aeolian environment because of rapider rate of destruction in comparison to water transporting factor. But the influence of wind on sandy material consist not only in changes in its features, but also in the spatial segregation of this material with prevailing wind direction (Pełka-Go�ciniak, 2000).

The aim of this paper is to present the record of wind influence on formation of sand deposits character in Biskupi Bór Basin, basing mostly on the quartz grain abrasion calculated by the method of B. Krygowski (1964). According to J. Go�dzik (2001) this method can be only referred for some grain sizes and results should be compared with other methods. Simultaneously this method seems to be one of the most objective.

To solve problem above-mentioned, archival material from 14 exposures and pits was used, and 244 samples of sandy material were analysed (Pełka-Go�ciniak, 2004). This material was collected along vertical lines in large sandpit at Bukowno, where sand was used as a stowing material for coal mines and glassworks. On its walls it was possible to observe the deep sandy series of different age. The top part of these series has been significantly remodelled by wind activity and it appeared in the form of aeolian coversands. Aeolian sands in Biskupi Bór Basin are mainly built of medium-grained deposit, which share amounts to on average to 50.95% and fluctuates between 22.9%-79.2%. Fine-grained material makes 27.1 % (1.1%-5.09%). Fraction >1.0 mm content is relatively small and amounts on average to 0.61% (0-4.72%). Admixture of dusty material is also small, its values fluctuates between 0%-6% (average value 0.95%). The value of mean grain diameter fluctuates between 0.18 mm and 0.5 mm (Mz=0.33 mm). Sands of older series are – in comparison to aeolian sands – coarser and better sorted (compare Pełka, 1992; Pełka-Go�ciniak, 2004).

From the analysis of spatial distribution for the particular coefficients of grain size distribution results, that within Biskupi Bór Basin simple surface trends presents the following variability (at assumption that the material transport run from the generally accepted western direction): coarsening and improvement in sorting (Pełka-Go�ciniak, 2004).

Results of analysis of quartz grain 1-0.8 mm abrasion were presented in figure 1, which is the synthetic picture of this feature of sands for the whole area investigated. It is possible to notice the large content of very well abraded grains of � type (reaching the value of 40%), big value of abrasion degree coefficient Wo (mean value=1252), even in very deep layers, as well as small content of angular grains of � type. Large content of well rounded grains and high values of Wo abrasion degree coefficient in every profile betoken that not only young aeolian series of coversands underwent the process of aeolisation. Maximum values of Wo or the shares of grains of � type not always occur in the top parts of profiles, i.e. within coversands.

It is also possible to state that in the analysed profiles (fig. 1) rather small increase of share of well rounded grains of � type from the bottom to the top of the sandy series is visible. Values of abrasion degree coefficient Wo observed along vertical line show very big differentiation, but the maximum ones occur at the depths of 10.5 m and 5. 5 m. In every profile the content of angular grains of � type is small and badly differentiated in a vertical line. It is possible to notice the weak increase of this type particles with the depth, what was also described by among others J. Go�dzik (1980).

Fig. 1. Quartz grain abrasion (1-0.8 mm) of sandy deposits in Biskupi Bór Basin (synthetic diagram): 1 – aeolian coversands, 2 – older sand series

In spatial distribution we can notice that aeolian sands in Biskupi Bór Basin are characterised by the

following variability together with prevailing wind direction: improvement of abrasion (increase in values of Wo coefficient) as well as increase in the content of well rounded grains of � , whereas the share of angular grains of � type decreases (Fig. 2). It proves the large influence of wind in the formation of textural features of these deposits.

Fig. 2. Spatial distribution of abrasion degree coefficient Wo, content of well rounded grains of � type and angular grains of � type for aeolian coversands in Biskupi Bór Basin

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Wind as a morphogenetic factor influenced the character of deposits filling Biskupi Bór Basin. The results of analysis of grain size distribution and quartz grains abrasion confirms that these deposits of generally fluvial origin have features typical for aeolian formations. But there are rather small differencies between aeolian coversands and older sandy series. The existence of material of a big quartz grain abrasion is also stated in other Polish fluvial Quaternary deposits. It is a common, but differential in quantity phenomenon (compare among others Dulias, 2003; Go�dzik, 1980, 1991).The wind influenced thickening, grain abrasion and sorting. The slight tendency to growth in degree of aeolisation from bottom towards top of sandy material is noticed. It means that the intensity of aeolian processes was increasing in course of time. The period of bigger aeolisation happened in the Vistulian. Later, younger phases of wind activity appear in a form of some typical aeolian series and they can be connected with the Late Vistulian, the beginning of Holocene, younger Holocene and present times (Pełka, 1992, Sendobry, 1988; Sendobry, Szczypek, 1991; Szczypek, 1988; Szczypek, Wach, 1991). Spatial distribution of abrasion degree coefficients clearly confirm these sands aeolisation.

References: Dulias R. (2003): Aeolisation of Quaternary deposits in O�wi�cim Basin, Carpathian Foredeep,

Geomorphologica Slovacia, 3: 12-18. Go�dzik J. (1980): Zastosowanie morfoskopii i graniformametrii do bada� osadów w kopalni w�gla brunatnego

Bełchatów. Studia Regionalne, 4 (9), PWN Warszawa-Łód�:101-114. Go�dzik J. (1991): Sedimentological record of aeolian processes from the Upper Plenivistulian and the turn of

Pleni-Late Vistulian in central Poland (In:) Kozarski S. (ed.) Late Vistulian (Weischelian) and Holocene Aeolian Phenomena in Central and Northern Europe, Z. Geomorph. N.F. Suppl., 90: 51-60.

Go�dzik J. (2001): O zale�no�ci miedzy pomiarami graniformametrycznymi a stopniem zaokrglenia ziarn, (w:) E. Mycielska-Dowgiałło (red.) Eolizacja osadów jako wska�nik stratygraficzny czwartorz�du, Uniwersytet Warszawski, Pracownia Sedymentologiczna WGiSR, Warszawa: 21-31.

Krygowski B. (1964): Graniformametria mechaniczna. Teoria, zastosowanie. PTPN, Prace Komisji Geograf.-Geolog, Pozna�, 2 (4): 1-112.

Pełka J. (1992): Rola wiatru w kształtowaniu cech osadów piaszczystych w Kotlinie Biskupiego Boru, (red. T. Szczypek) Wybrane zagadnienia geomorfologii eolicznej, SGP, WNoZ, Sosnowiec: 129-140.

Pełka-Go�ciniak J. (2000): Przestrzenna zmienno� piasków eolicznych Pustyni Starczynowskiej, U�, WNoZ, Sosnowiec: 1-75.

Pełka-Go�ciniak J. (2004): Przestrzenna zmienno� cech piasków eolicznych wschodniej cz��ci Wy�yny �lskiej, (w:) J. Wojtanowicz (red) Formy i osady eoliczne, SGP Pozna�: 36-44.

Sendobry K. (1988): Uwagi o wyst�powaniu i genezie struktur mrozowych w Kotlinie Biskupiego Boru. (w:) Problemy paleogeografii czwartorz�du - zlodowacenia �rodkowopolskie (red. J. Jersak), U�, Katowice: 77-87.

Sendobry K., Szczypek T. (1991): Geneza i wiek podkuestowych osadów piaszczystych w okolicach Olkusza. Geographia, studia et dissertationes, t. 15, U� Katowice: 88-104.

Szczypek T. (1988): Działalno� eoliczna we wschodniej cz��ci Wy�yny �lskiej na przykładzie okolic Bukowna, Geographia, studia et dissertationes, 11, U�, Katowice: 7-22.

Szczypek T., Wach J. (1991): Rozwój współczesnej wydmy w warunkach silnej antropopresji, U� Katowice: 1-79.

Streszczenie

Eolizacja osadów piaszczystych w Kotlinie Biskupiego Boru (wschodnia cz��� Wy�yny �l�skiej – południowa Polska)

W pracy przedstawiono rol� wiatru w kształtowaniu cech osadów piaszczystych w Kotlinie Biskupiego Boru we wschodniej cz��ci Wy�yny �lskiej. Analiz� przeprowadzono w oparciu o archiwalny materiał badawczy zebrany w piaskowni w Bukownie. Wykonano syntetyczny wykres obrazujcy cechy obróbki we wszystkich analizowanych profilach (rys. 1), jak równie� schematy przestrzenne ilustrujce zmienno� wska�ników obtoczenia: zawarto�ci ziaren okrgłych � oraz ostrokraw�dzistych � oraz wska�nika obróbki Wo (rys. 2). Stwierdzono wysoki stopie� obróbki ziaren kwarcu zarówno w piaskach eolicznych, jak i w osadach najogólniej pochodzenia rzecznego. Dowodem na eolizacj� piasków w Kotlinie Biskupiego Boru w porównaniu ze starszymi seriami jest ich lepsze obtoczenie (wzrost zawarto�ci ziaren � oraz warto�ci Wo), natomiast w uj�ciu przestrzennym wzrost tych parametrów zgodnie z dominujcym zachodnim kierunkiem wiatru.