PETROLOGY AND PALYNOLOGY OF THE NO 5 BLOCK COAL BED, NORTHEASTERN KENTUCKY

The upper Middle Pennsylvanian (middle Westphalian D equivalent) No. 5 Block coal bed (Eastern Kentucky Coal Field of the Central Appalachia n Basin) is a low-sulfur, compliance coal resource, dominantly compris ed of dull, inertinite-rich lithotypes. Ash yields tend to be highly v ariable in the No. 5 Block, as does bed thickness and frequency of bed splitting. This study describes the petrographic, palynologic and geo chemical characteristics of the No. 5 Block coal bed, and reports on s ome temporal and spatial trends among these parameters in eastern-nort heastern Kentucky. Petrographically the No. 5 Block coal is predominat ed by dull, often high-ash lithotypes, with inertinite contents common ly exceeding 30% (mmf). The coal thins to the north-northwest where it tends to be higher in vitrinite and sulfur content. Representatives o f large and small lycopsids and ferns (both tree-like and small variet ies) dominate the No. 5 Block coal bed palynoflora. Calamite spores an d cordaite pollen also occur but are less abundant. Small lycopsid (De nsosporites spp. and related crassicingulate genera) and tree fem (e.g . Punctatisporites minutus, Laevigatosporites globosus) spore taxa are most abundant in dull lithotypes. Bright lithotypes contain higher pe rcentages of arboreous lycopsid spores (Lycospora spp.). Regionally, t he No. 5 Block coal contains abundant Torispora securis , a tree fem s pore specially adapted for desiccation prevention. This, along with ov erall high percentages of inertinite macerals, suggest that peat accum ulation may have taken place in a seasonally dry (?) paleoclimate. The No. 5 Block coal bed thickens rather dramatically in a NW-SE directio n, as does the frequency of coal bed splitting. This phenomenon appear s to be related to increased accommodation space in the southeastern p ortion of the study area, perhaps via penecontemporaneous growth fault ing. Maceral and palynomorph variations within the bed correspond with these changes. Thin coal along the northwestern margin tends to be vi trinite rich and contains abundant Lycospora, perhaps reflecting relat ively stable peat-forming conditions. Thicker coal to the southeast co ntains more inertinite, high-ash coal layers, and inorganic partings. Spore floras contain more small lycopsid and tree fern components and are temporally variable, perhaps indicating a more unstable peat-formi ng environment.