Subtle structural influences on coal thickness and distribution: Examples from the Lower Broas–Stockton coal (Middle Pennsylvanian), Eastern Kentucky Coal Field, USA

Abstract

The Lower Broas-Stockton coal is a heavily mined coal of the Central Appalachian Basin. Coal thickness, distribution, composition, and stratigraphic position were compared with basement structure, gas and oil field trends, and sequence stratigraphic and paleoclimate interpretations to better understand the geology of the Stockton coal bed in eastern Kentucky. The thickest coal occurs south of the Warfield structural trend and east of the Paint Creek Uplift, two basement-related structures. Along the Warfield trend, coal beds in the underlying Peach Orchard coal zone locally merge with the Stockton coal to form a seam more than 3 m thick. Other areas of thick coal occur in elongate trends. Two pairs of elongate, conjugate trends in Stockton coal thickness are interpreted as regional paleofractures that influenced paleotopography and groundwater during peat accumulation.Compositional group analyses indicate that the Stockton peat infilled depressions in the paleotopography as a topogenous to soligenous mire codominated by tree ferns and lycopsid trees. Flooding from adjacent paleochannels is indicated by partings and seam splits along the margins of the mineable coal body. One or more increments of low-vitrinite coal, dominated by tree ferns and shrubby, Densosporites-producing lycopsids occur at all sample sites. Similar assemblages have been previously used to identify ombrogenous, domed mire origins for Early and Middle Pennsylvanian coals in which ash yields were less than 10%. It is difficult, however, to reconcile ombrogenous conditions with the partings in the Stockton coal in this area. Low-ash, low-vitrinite increments may have been formed in topogenous to soligenous mires with periodic drying or water-table fluctuations, rather than widespread doming. This is consistent with interpretations of increasingly seasonal paleoclimates in the late Middle and Late Pennsylvanian and fracture-influenced groundwater conditions.

Control of Relative Sea Level and Climate on Coal Character in the Westphalian C (Atokan) Four Corners Formation, Central Appalachian Basin, U.S.A.

“…3; Jerrett et al 2011) demonstrated that similar accommodation cycles can be correlated over distances greater than 100 km. Less detailed (bench-or ply-scale) petrographic, palynological, and geochemical studies of numerous coals from the upper Breathitt Group also indicate that vertical changes in coal seam-compositions are readily traceable over tens of kilometers, at least (e.g., Hower and Pollock 1988;Hower and Bland 1989;Eble and Grady 1990;Helfrich and Hower 1991;Hower et al 1991;Raione et al 1991;Hatton et al 1992;Eble et al 1994;Hower et al 1994;Hower et al 1996;Greb et al 1999;Rimmer et al 2000;Greb et al 2002;Greb et al 2005;Hower et al 2005). The scale of the correlations demonstrated by these studies points to an allogenic control on water table dynamics in the precursor mires, and in view of the hydrologic connection of the coastal-plain water table to sea level, it is logical to assume that high-resolution accommodation cycles in the coals of the Four Corners Formation represent subtle responses in the peat stratigraphy to high-frequency sea-level oscillations.…”

“…9 Coal at the Four Corners locality is a local anomaly, since it is recognized regionally (Fig. 4) and is one of the most extensively mined through eastern Kentucky and into West Virginia (Greb et al 2005). The thick, low-vitrinite/inertinite Hazard No.…”

Fault‐block rotation controlling the distribution of fluvial sediments; a quantitative test on a Lower Pennsylvanian (Carboniferous) cyclothem succession

“…The change in coal thickness over short distances may be related to infilling of inherited floodplain topography (Greb & Chesnut, ; Greb et al ., ), but overall coal thickness increases towards the downthrown sides of faults, which indicates that synsedimentary faulting and related differential subsidence played a role (cf. Guion & Fielding, ; Greb et al ., , ).…”

Carboniferous–Permian Coaly Source Rock Formation in North China: Implications from Geochemical Characteristics and Depositional Environments

“…The combustion of coal has been widely used to provide energy and electricity for industrial development. − Residual coal slag has been utilized as a secondary heat source in the manufacture of building materials. , Moreover, additional coal-derived petroleum reservoirs and coalbed gas reservoirs such as the coal-related methane in Carboniferous coal seams of the Donets Basin and coal-derived gas from the Shanxi Formation of the Ordos Basin and Bohai Bay Basin have been discovered worldwide. Many researchers have studied coal accumulation by focusing on sequence stratigraphy, depositional environment, and coal composition. − The roles played by subtle structure and sequence stratigraphy were proposed as keys to coal formation. − Paleoecology, paleo-flora composition and distribution, and formation environments were also confirmed to control coal deposition. ,, The method of formation and the hydrocarbon generation potential of coaly shale source rocks were determined to vary widely by the depositional period (e.g., coal in the Sydney coalfield of Canada was deposited in an extensive coastal platform and derived from Ammobaculites-Ammotium assemblages and Troehammina, Ammotium, and Ammobaculites; ,,− ). However, there is little available research on the method of OM accumulation or models of coaly source rocks.…”