Palynologic, petrographic and geochemical characteristics of the Manchester coal bed in Eastern Kentucky

The Manchester coal bed in eastern Kentucky is the stratigraphically lowest coal in Kentucky that is both laterally continuous and of consistent mineable thickness. The Manchester coal bed occurs in the lower part of the Breathitt Formation, in an interval between the underlying Corbin Sandstone and the overlying Betsie Shale, both of which are also aerially widespread units. The Manchester is early Middle Pennsylvanian in age and is equivalent with the middle Morrowan of the Eastern Interior Basin and the late Westphalian A of western Europe. Increment samples were collected from the western and eastern outcrop and mining areas of the Eastern Kentucky Coal Field and were analyzed palynologically, petrographically and geochemically to compare and contrast the two areas. In the western part of the Eastern Kentucky Coal Field, the Manchester coal bed is uniform in occurrence and composition. The bed is consistently 0.61–0.92 m (2–3 ft) thick, and generally is devoid of inorganic partings. Palynologically, the coal in this area is largely dominated by Lycospora, the dispersed spore of many of the large lycopsid trees (e.g., Lepidodendron and Lepidophloios) and, to a lesser extent, Granasporites medius (representing Diaphorodendron and Synchysidendron). Petrographically, the coal contains high percentages of vitrinite macerals and correspondingly low percentages of liptinite and inertinite macerals. Most of the increments from this area studied are generally low in ash yield ( >5%) and sulfur content ( 10%) and occasionally sulfur ( > 1%). In the eastern part of the coal field the Manchester coal bed is typically thicker ( > 3 ft, 1 m), but usually occurs as a coal zone with intercalated coal beds and clastic units. Palynologically, the coal in this area contains increased percentages of small lycopsid, small (seed?) ferns, calamites, and cordaites. Petrographically, the coal is higher overall in liptinite and inertinite macerals. Ash yields in the eastern sample area are generally low ( < 10%), an exception being some high-ash durain bands. Overall sulfur contents also are low (typically < 1%). The western samples are interpreted as having formed in a well protected, generally flooded, mire. A consistent water cover would provide a favorable environment for arboreous lycopsid growth and proliferation, and also inhibit oxidation of the peat surface, thus promoting the formation of a high vitrinite content coal. The eastern samples are also interpreted as having formed in a mire that was well protected most of the time, giving rise to thick sequences of low-ash, low-sulfur coal. Intermittent inundation by extra-swamp waters, carrying sediment in this area, resulted in the development of a multiple coal zone (i.e., several peat-forming events with intervening clastic deposition), in contrast to a single peat-forming event in the western area. Surficial peat exposure was more frequent in the eastern area, which allowed for increased microbial degradation of the peat and subsequent formation of inertinite macerals upon conversion to bituminous coal. This condition might also accelerate charring of the peat surface by wildfire.