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Organic geochemical study of sequences overlying coal seams; example from the Mansfield Formation (Lower Pennsylvanian), Indiana

International Journal of Coal Geology

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Abstract

Roof successions above two coal seams from the Mansfield Formation (Lower Pennsylvanian) in the Indiana portion of the Illinois Basin have been studied with regard to sedimentary structures, organic petrology and organic geochemistry. The succession above the Blue Creek Member of the Mansfield Formation is typical of the lithologies covering low-sulphur coals (< 1%) in the area studied, whereas the succession above the unnamed Mansfield coal is typical of high-sulphur coals (> 2.%). The transgressive-regressive packages above both seams reflect the periodic inundation of coastal mires by tidal flats and creeks as inferred from bioturbation and sedimentary structures such as tidal rhythmites and clay-draped ripple bedforms. Geochemistry and petrology of organic facies above the Blue Creek coal suggest that tidal flats formed inland in fresh-water environments. These overlying fresh water sediments prevented saline waters from invading the peat, contributing to low-sulphur content in the coal. Above the unnamed coal, trace fossils and geochemical and petrological characteristics of organic facies suggest more unrestricted seaward depositional environment. The absence of saline or typically marine biomarkers above this coal is interpreted as evidence of very short periods of marine transgression, as there was not enough time for establishment of the precursor organisms for marine biomarkers. However, sufficient time passed to raise SO42- concentration in pore waters, resulting in the formation of authigenic pyrite and sulphur incorporation into organic matter.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Organic geochemical study of sequences overlying coal seams; example from the Mansfield Formation (Lower Pennsylvanian), Indiana
Series title:
International Journal of Coal Geology
Volume
33
Issue:
4
Year Published:
1997
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
International Journal of Coal Geology
First page:
275
Last page:
299
Number of Pages:
25