Coal seams of the Walbrzych formation, Intrasudetic Basin, Poland: inferences on changing depositional environment
ABSTRACT The petrological composition of coal seams of the Walbrzych Fm. was studied, and depositional conditions were reconstructed on the basis of both coal and clastic sediment analysis. Coal of this formation is of medium- to low-volatile bituminous rank; vitrinite reflectance Ro max ranges from 0.8 to 2.0% and volatile matter content from 29 to 16%.The coal seams of the Walbrzych Formation contain mainly banded coal; bright and dull lithotypes occur sporadically. The amount of banded and banded dull coals increases towards the top of the formation at the expense of banded bright coal. Consequently, vitrinite and vitrite content tends to decrease upwards. Peat deposition in the lower part of the Walbrzych Formation occurred predominantly in a telmatic forest zone. The mires were located between interdistributary channels on a delta plain, and they were probably ombrotrophic. In the upper part of the Walbrzych Formation, swamps were the primary sites of peat deposition. Abandoned channels were favoured as peat deposition sites for seams where increases in seam thickness are associated with increases in coarse clastic content below seams. Continuous peat deposition in overbank zones is postulated for seams wherein decreases in seam thickness are associated with increases in coarse clastic content. Where no relationship between seam thickness and coarse clastic content beneath the seam exists, the swamp may have encroached into overbank and channel zones rapidly. Changes in the environment of peat deposition may be related to tectonic activity along the basin margins during the Namurian.
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ABSTRACT: The Carboniferous succession of the Intrasudetic Basin is an important source of medium- and low-volatile bituminous coal in Poland. Three lithostratigraphic 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 Intrasudetic Basin was very favorable for peat deposition during Namurian A times and coal seams generally are thicker in this region. In some seams, the greates seam thickness occurs along the eastern margin of the basin. Seam thickness in seam 678 is relatively uniform, whereas coal and clastic parting thickness varies greatly in seams 672 and 664/665. 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 content. In contrast, the greatest thickness in seam 664/665 is associated with floodplain sediments. In such regions, bright coal/clastic parting couplets occur repetitively proximal to natural levees, whereas duller coal with few dirt bands is characteristic of the central part of backswamps. Peat deposition in the lower part of the Walbrzych Formation occurred dominantly in ombrotrophic mires, whereas swamps were primary sites of peat deposition in the upper part of this formation. Coal quality parameters vary considerably within each seam and more data are needed to determine the factors influencing them.Palaeogeography Palaeoclimatology Palaeoecology 01/1994; 106(1-4):157-169. DOI:10.1016/0031-0182(94)90008-6 · 2.75 Impact Factor
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ABSTRACT: Extensive Westphalian D to Stephanian coal seams divide the Sydney Mines Formation of Cape Breton Island into large-scale repetitive sedimentary packages. The Backpit seam, one of the most continuous seams within this formation, was studied in detail to establish compositional trends and relate these to paleomire development within an overall transgressive setting. The seam is of high-volatile B to A bituminous rank and ranges in thickness from 0.6 to 1.5 m onshore. Agglutinated foraminifera occur in strata directly below and above the seam, indicating a coastal setting for the mire. Ash and sulphur contents average 15.3 ± 6 and 5.2 ± 2%, respectively. Sulphur, predominantly in the form of pyrite, increases near the roof of the seam, consistent with a brackish influence in the roof strata.The planar Backpit mire was subjected to widespread, periodic flooding, marked by thin dull to coaly shale lithotype intervals. Some intervals can be correlated across the onshore portion of the basin for more than 45 km and this distribution suggests regional controls on their formation. Seam lithology changes frequently in vertical section and banded lithotypes predominate. Vitrinite macerals and vitrinite-rich microlithotypes are abundant and thin discrete fusain bands, the remains of ancient fires, are also common. Coal facies patterns record a series of wetting upward pulses in the upper portion of the seam that culminated in the drowning and termination of the mire. A broad, relatively shallow embayment subsequently formed that supported a fresh- to brackish water fauna.Palaeogeography Palaeoclimatology Palaeoecology 01/1994; 106(1-4):223-239. DOI:10.1016/0031-0182(94)90012-4 · 2.75 Impact Factor
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ABSTRACT: The petrographic and palynologic compositions of coal seams of the Żacler formation (Upper Carboniferous, Westphalian A) from northwestern and southeastern part of the Lower Silesian Coal Basin (LSCB) were examined. Coals studied are highly volatile bituminous coal, where Ro ranges from 0.91% to 1.09%. Seam 430 from the northwestern part of the basin contains high vitrinite percentage with rather low inertinite and liptinite contents, while percentage of mineral matter is variable. This petrographic composition is associated either with a predominance of Lycospora in miospore assemblage, or with a miospore assemblage of mixed character. The abundance of Lycospora reflects vegetation composed of the arborescent lycopsids while the mixed miospore assemblage is connected with diverse palaeoplant communities, namely, arborescent lycopsids, calamites and ferns. Seams 409 and 412/413 from the southeastern part of the LSCB are rich in inertinite and liptinite, while the vitrinite content is moderate. Their characteristic feature is the occurrence of a diagnostic crassisporinite (densosporinite). Amount of the mineral components in these coals is very low. Densosporites and related crassicingulate genera are main components of these miospore assemblages and were produced by herbaceous and/or sub-arborescent lycopsids. These petrographic and palynologic features were the basis for distinguishing three maceral–miospore associations: an arborescent lycopsid and mixed associations, occurring in the seam 430 and a herbaceous and/or sub-arborescent lycopsid association which was recorded in seams 409 and 412/413. The first two assemblages are interpreted as having been deposited in a planar rheotrophic mire, whereas the herbaceous and/or sub-arborescent lycopsid association is thought to have developed in an ombrotrophic, domed mire.International Journal of Coal Geology 07/1999; DOI:10.1016/S0166-5162(99)00007-5 · 3.31 Impact Factor