Early Pennsylvanian ombrotrophic mire of the Prokop Coal (Upper Silesian Basin); what does it say about climate?
Abstract
The Lower Pennsylvanian (Kinderscoutian) Prokop Coal (Coal No. 40), the erosional remnant of which covers about 5000 km(2), is the thickest seam of the Upper Silesian Basin situated along the Czech - Polish border. This basin-wide coal is unusual in its thickness and high inertinite and very low ash contents.
In the Czech sector, this coal merges with the overlying Coal No. 39 into a single 9 to 15 m thick seam. Maceral analyses of an approximately 11 m thick section of these two merged coals show changes in the proportion of vitrinite (24.7 - 88.0%) and inertinite (8.5 - 56.8%) in cycles between 50 and 190 cm thick.
The increase of inertinite in the lower part of coal cycles coincides with a dulling-upward trend, which records a drying-upward succession due to a slowing of accommodation rate relative to plant biomass productivity. This succession is interpreted as a transition from rheotrophic to ombrotrophic conditions.
The brightening-upward succession in the upper part of coal cycles records a wetting-upward trend due to water table rise, resulting in restoration of rheotrophic conditions that supported humification under the regional ground water table. The sudden shift from inertinite-rich to vitrinite-rich coal at the base of brightening-upward successions points to a period of degradation and lowering of the peat dome.
The coal cycles within the studied seam section probably preserve a succession of spatially overlapping but genetically independent mires bounded by degradation surfaces. The alternation between mires with contrasting hydrological regimes is interpreted as a record of base-level fluctuations of climatic causation of sub-Milankovitch periodicities.
Early Pennsylvanian climate for various stages of mire development is inferred from analogy with modem tropical mires in SE Asia.