Uwagi o litologii i genezie trzeciorzędowych wapieni jeziornych ze złoża węgla brunatnego Bełchatów

Abstract

Opisano warunki występowania oraz charakterystykę chemiczną i petrograficzną węglanowych utworów występujących w formacji węgla brunatnego złoża Bełchatów. Przeanalizowano pozycję tych utworów w różnych klasyfikacjach skat węglanowych. Przedstawiono uwagi o warunkach sedymentacji chemogenicznych osadów węglanowych, określonych jako wapienie jeziorne, na tle sedymentacji osadów serii węgla brunatnego w rowie Kleszczowa. REMARKS ON LITHOLOGY AND ORIGIN OF TERTIARY LACUSTRINE LIMESTONES IN THE BEŁCHATÓW BROWN-COAL DEPOSIT The Tertiary infill of the Kleszczów Trough comprises some carbonate sediments. The sediments, yielding varying amounts of coal matter and remains of fresh-water molluscans, are known as lacustrine limestones. They mainly occur in upper, supra-coal part of the deposit series, being represented by subordinate intercalations in the middle, coal-bearing part. Thickness of the limestones is the highest in proximity of trough margins, clearly decreassing towards central part of the trough. This suggests that carbonate material of the limestones is related to Mesozoic carbonate rocks, in which the Kleszczów Trough is developed.The lacustrine limestones are poorly cohesive, porous, white-gray to dark-brown in colour, with varying content of remains of fresh-water shelly fauna. Variability in colour appears related to differences (marked) in admixture of coal matter. Microcrystalline calcite is the major mineral component of these sediments whereas clay minerals, quartz pelite, and matter occur as admixtures only. Calcite forms micritic groundmass in which allochems and detrital components are embedded. With reference to the currently used classifications of carbonate rocks, the lacustrine limestones are interpreted as biomicrites (R.L. Folk, 1959), mudstones passing into wackestone (R.J. Dunham; 1962), and micritic-biogenic limestones passing into biogenic-micritic ones (M.W. Leighton, C. Pendexter, 1962). The limestones represent a chemical sediment as carbonate material derived from weathering of carbonate margins of the trough precipitated as a calcite mud in lacustrine basins. To the same basins there was also supplied detrital material and coal matter coming from erosion of previously formed coal layers.Because of high content of CaO (44-53%) and marked admixture of organic matter, the lacustrine limestones should be used as a mineral fertilizer in agriculture.