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Depositional environments of the Jurassic maghara main coal seam in north central Sinai, Egypt
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SYSNO ASEP 0496698 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Depositional environments of the Jurassic maghara main coal seam in north central Sinai, Egypt Author(s) Edress, N.A.A. (EG)
Opluštil, S. (CZ)
Sýkorová, Ivana (USMH-B) RID, ORCIDSource Title Journal of African Earth Sciences. - : Elsevier - ISSN 1464-343X
Roč. 140, APR (2018), s. 241-255Number of pages 15 s. Publication form Print - P Language eng - English Country GB - United Kingdom Keywords Maghara main coal ; Lithotypes ; macerals ; Jurassic ; Egypt Subject RIV DB - Geology ; Mineralogy OECD category Geology Method of publishing Limited access Institutional support USMH-B - RVO:67985891 UT WOS 000427999500017 EID SCOPUS 85044631045 DOI 10.1016/j.jafrearsci.2018.01.017 Annotation Twenty-eight channel samples with a cumulative thickness of about 4 m collected from three sections of the Maghara main coal seam in the middle Jurassic Safa Formation have been studied for their lithotype and maceral compositions to reconstruct the character of peat swamp, its hydrological regime and the predominating type of vegetation. Lithotype composition is a combination of dully lithotypes with duroclarain (19% of total cumulative thickness), clarodurain (15%), black durain (15%), and shaly coal (15%) and bright lithotypes represented by clarain (23%), vitrain (12%) and a small proportion of wild fire-generated fusain (1%). Maceral analyses revealed the dominance of vitrinite (70.6% on average), followed by liptinite (25.2%) and inertinite (8.1%). Mineral matter content is ∼9% on average and consists of clay, quartz and pyrite concentrate mostly at the base and the roof of the seam. Dominantly vitrinite composition of coal and extremely low fire- and oxidation-borne inertinite content, together with high Gelification Indices imply predomination of waterlogged anoxic conditions in the precursing mire with water tables mostly above the peat surface throughout most of the time during peat swamp formation. Increases in collotelinite contents and Tissue Preservation Index up the section, followed by a reversal trend in upper third of the coal section, further accompanied by a reversal trend in collodetrinite, liptodetrinite, alginite, sporinite and clay contents records a transition from dominately limnotelmatic and limnic at the lower part to dominately limnotelmatic with increase telmatic condition achieved in the middle part of coal. At the upper part of coal seam an opposite trend marks the return to limnic and limnotelmatic conditions in the final phases of peat swamp history and its subsequent inundation. The proportion of arborescent (mostly coniferous) and herbaceous vegetation varied throughout the section of the coal with tendency of increasing density of arborescent vegetation to the middle part of the coal seam section. The intercalation of coal in shallow marine strata implies that peat swamp precursor formed in a coastal setting, probably on delta plain or lagoon. Its formation was controlled by water table changes driven by sea level fluctuations that created an accommodation space necessary for preservation of peat. Workplace Institute of Rock Structure and Mechanics Contact Iva Švihálková, svihalkova@irsm.cas.cz, Tel.: 266 009 216 Year of Publishing 2019
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