VARIATIONS IN SEAM THICKNESS, COAL TYPE AND COAL QUALITY IN THE NAMURIAN SUCCESSION OF THE INTRASUDETIC BASIN (SOUTHWESTERN POLAND)

The Carboniferous succession of the Intrasudetic Basin is an important source of medium- and low-volatile bituminous coal in Poland. Three l ithostratigraphic units comprise this succession: the Walbrzych, Bialy Kamien and Zacler Formations. The Walbrzych Formation (Namurian A) is a 300 m thick (maximum) succession that is composed of fining-upward cyclothems with over twenty coal seams. The northern part of the Intra sudetic Basin was very favorable for peat deposition during Namurian A times and coal seams generally are thicker in this region. In some se ams, the greatest seam thickness occurs along the eastern margin of th e basin. Seam thickness in seam 678 is relatively uniform, whereas coa l and clastic parting thickness varies greatly in seams 672 and 664/66 5. In seam 672, the greatest seam thickness occurs above channel zones , which suggests that abandoned channels were sites favorable for peat deposition. Coal in such zones is typified by increased liptinite con tent. In contrast, the greatest thickness in seam 664/665 is associate d with floodplain sediments. In such regions, bright coal/clastic part ing couplets occur repetitively proximal to natural levees, whereas du ller coal with few dirt bands is characteristic of the central part of back-swamps. Peat deposition in the lower part of the Walbrzych Forma tion occurred dominantly in ombrotrophic mires, whereas swamps were pr imary sites of peat deposition in the upper part of this formation. Co al quality parameters vary considerably within each seam and more data are needed to determine the factors influencing them.