An in situ occurrence of coal balls in the Amburgy coal bed, Pikeville Formation (Duckmantian), central Appalachian Basin, USA

Carbonate concretions containing permineralized pest, commonly called coal balls, were encountered in the Amburgy coal, a generally low-ash (9.4 %) bu t commonly high-sulfur (3.6 %) Middle Pennsylvanian coal of the Eastern Ken tucky Coal Field. These are the first coal balls from the Amburgy coal, and one of only a few reported occurrences fi om the central Appalachian Basin . The coal balls occur in the upper part of the coal, between two paleochan nel cutouts at the top of the Pikeville Formation, and immediately beneath a scour with a marine fossil lag at the base of the Kendrich Shale Member, Hyden Formation. The coal is thickest (1.3 m) in a narrow (<300 m) elongate depression between the bounding paleochannels, and thins toward the occurr ence of coal balls. Total biovolume as measured from acetate peels of coal balls indicates cordaites or lycopsid (36.1 % each) dominance. Vertical sam pling through one coal-ball aggregate shows zoning from a lower cordites-do minant (88.7%) assemblage, to a middle, degraded sphenopsid-rich assemblage , to an upper lycopsid-dominant (88.6%) assemblage. Beneath the coal balls, palynologic and petrographic analyses indicate the basal and middle portio ns of the bed are dominated by arborescent lycopsid spores and cordaites po llen, and by vitrinite macerals. The top part of the bed above the coal bal ls, contains increased inertinite macerals, increased percentages of small fern spares, and variable ash yield (5-21%). Thickening of the Amburgy coal along a structural low, in combination with basal high-ash yields, vitrinite-dominance, and heterogenous palynoflora, i ndicate paleotopographic control on initial peat accumulation. Abundant lyc opsid spores in the basal and middle part of the coal reflect rheotrophic c onditions consistent with accumulation in a paleotopographic depression. Ap parent zonation preserved in one of the coal-ball masses may document plant successions in response to flooding. Similar percentages of cordaites and lycopods, respectively, in the zones above and below the degraded incursion interval reflect development of a mixed successional pattern, in response to the flooding. Coal-ball formation. may have been facilitated by channeli ng along the Kendrick ravinement, within a paleotopographic depression at t he split margin of the Amburgy peat, either through direct transmittal of c arbonates and marine waters into the peat, or through degassing of the peat beneath the scour.