The anatomy of a coal seam split,Durham coalfield,Northeast England

A pronounced coal seam split, one of many within the Lower Westphalian B (Upper Carboniferous) sequence of the Durham coalfield, northeast England, occurs in the vicinity of the village of Burnhope. This feature involves the division of the combined Main/Fivequarter coal into its two component parts, which become separated by up to 8 m of clastic sedimentary rocks over a horizontal distance of 150 m. Three-dimensional outcrop data from an opencast (surface) coal mine straddling the split, supported by extensive subsurface information, have allowed detailed study of the seam split geometry, in addition to that of three overlying coal seams and intervening clastic facies. The study suggests that deposition of the interval as a whole, including the split, was strongly influenced by compaction-controlled subsidence, and not by either contemporary fault movements or channel sedimentation. A substantially greater aggregate thickness of coal is preserved over the five seam interval where the Main/Fivequarter is unsplit than where split. This relationship is consistent with the coal depositional model proposed by Fielding (1984a), which proposed that thick coals in the Durham area are located adjacent to, but not within, coal seam splits. It further implies that attractive sites for future opencast development in the area may be predicted from a regional knowledge of coal seam splits.