Geologos, 2011, 17, 4
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Item Alternative interpretations of grain-size data from Quaternary deposits(Wydawnictwo Naukowe UAM, 2011) Mycielska-Dowgiałło, Elżbieta; Ludwikowska-Kędzia, MałgorzataSeveral possibilities to present and to interpret the results of granulometric analyses of Quaternary fluvial, aeolian, glacial and wash-out slope deposits were investigated. Attention is paid particularly to the cumulative curves at a probability scale and the frequency curves, and it is shown how these curves can help to determine the sedimentary environment. The inclination of the cumulative curves in the part of the maximum proportion of a particular grain size appears significant. It appears possible to obtain information on the density and dynamics of the transporting medium from the course of the cumulative curves (inclination and spread of grain size). The examination of textural parameters allows to draw regression lines characteristic of both deposits from various sedimentary environments and deposits from one single environment but with different histories as to their transport dynamics.Item Grain-size distribution analysis of Quaternary sediments from the southern part of the Lodz region in Poland: a computational-methods approach(Wydawnictwo Naukowe UAM, 2011) Wachecka-Kotkowska, Lucyna; Kotkowski, PawełEighteen samples of Quaternary unconsolidated sediments from the Piotrków Plateau and the Radomsko Hills in central Poland have been analysed for their average grain size, sorting, skewness and kurtosis. The analysis was carried out by seven computational methods of interpolation and nine extrapolation methods. It appears that linear interpolation, the traditional method (DOS), and the Josek and Gradistat Programs give comparable results, but that quadratic interpolation and the method of moments should not be applied since they yield unreliable results. The method of moments gives unduly high or unduly low parameter values because of the application of different, i.e. incomparable measures in the applied formulae. It should be stressed that only extrapolation provides, if performed under the right conditions, the possibility to determine some parameters, in particular skewness values.Item Palaeoslopes of Weichselian sand-bed braided rivers in the Toruń Basin (Poland): results of a palaeohydraulic analysis(Wydawnictwo Naukowe UAM, 2011) Weckwerth, PiotrPalaeoslopes of Weichselian sand-bed braided rivers have been reconstructed for two stages of fluvial development in the Toruń Basin. (1) The palaeoslope of the ‘fossil’ fluvial succession (buried under Weichselian tills) was calculated on the basis of the median grain size and the Shields parameter. The hydraulic gradient thus found is comparable with the hydraulic gradient of the present-day river. (2) The second developmental stage of the Toruń Basin (as a apart of the Noteć-Warta ice-marginal valley) took place after deglaciation. The slopes of river terraces are a few times lower than those calculated on the basis of the Shields parameter. The palaeoslope of the then river was estimated on the basis of a constant interdependency between the braidplain width, the channel geometry and the grain size. The river gradient that was thus calculated is similar to the measured terrace slope. Palaeoslope estimates in valleys similar to those in the Toruń Basin should consider the width of the braidplain.Item Adjustment coefficients for planimetric analysis of the granulometry of coarse-grained sediments(Wydawnictwo Naukowe UAM, 2011) Pisarska-Jamroży, Małgorzata; Kossowski, Tomasz; Jamroży, JerzyThe relationship between results from granulometric analyses of by sieving and by planimetry was investigated by numerical simulation of cubes filled with boulders, cobbles and pebbles. Cross-sections through the sediment were simulated and compared with photos of an actual outcrop wall. Volumes estimated on the basis of planimetric analysis using the cross-sections were compared with sieve analyses, thus allowing to determine adjustment coefficients. The coefficients for pebbles and cobbles have a small standard error, but are larger for boulders, which might be a consequence of too small areas formed by the cross-sections.