Sedimentary facies of the coal-bearing Westphalian A and B north of the Wales-Brabant High

Abstract

Important coal deposits are present in Britain north of the Wales-Brabant High in the Pennine Basin, which was initiated by late Devonian to early Carboniferous extension. The formation of coals of sufficient thickness, quality and continuity to be commercially exploited was favoured during the latest Westphalian A (Langsettian) and much of the Westphalian B (Duckmantian), when deposition took place in an environment similar to an upper delta plain, with limited marine influence. During the early part of the Westphalian A, marine influence was important, with the consequence that the coals were thinner, less persistent and of inferior quality. By the late Westphalian, alluvial deposition became important, and coals of commercial quality are rare.Accurate determination of facies, lithological attributes and geometry is an important tool in exploration and mine planning. Sedimentary facies have thus been rationalized into those that may be consistently recognizable in boreholes and mine workings. However, facies may be further subdivided when conditions allow, and intermediate facies exist, reflecting the complexities of depositional environments. The characteristics of the following facies are described here: mire, palaeosol,/narine, lacustrine, lacustrine delta, major channel, minor channel, overbank and crevasse splay. Channel deposits have a number of adverse effects on mining and the range of channel-fill deposits reflects the operation of many different processes.A model of sedimentation is presented which emphasizes that local sedimentary and autocyclic processes, local tectonics, subsidence and compaction were important in controlling the distribution of facies at a mine scale.

New high-precision U–Pb dates from western European Carboniferous tuffs; implications for time scale calibration, the periodicity of late Carboniferous cycles and stratigraphical correlation

“…Only 19 bands are recognized from the Pennine Basin (Calver 1968;Ramsbottom et al 1978); most occur in the early Langsettian and the late Duckmantian to early Bolsovian (Calver 1968(Calver , 1969. The reduction in the number of marine bands during mid to late Langsettian times is coincident with an increased prevalence of non-marine mussel bands (Calver 1968(Calver , 1969 and sedimentological changes that suggest a landward shift in the depositional environment from a lower to an upper delta plain (Guion & Fielding 1988;Guion et al 1995).…”

Provenance of late Carboniferous sandstones in the Pennine Basin (UK) from combined heavy mineral, garnet geochemistry and palaeocurrent studies

“…The great majority of late Carboniferous sandstones in the Pennine Basin are of fluvial origin (Collinson, 1988;Guion and Fielding, 1988;Guion et al, 1995) and the palaeocurrent directions shown by cross-bedding relate to fluvial subenvironments, mainly channels, crevasse splays, and mouthbars of deltas.…”

Geological controls on the sulphur content of coal seams in the Northumberland Coalfield, Northeast England

“…Thus, the coastal plain was influenced by relative sea level fluctuations even though well separated from the shoreline and very distal (N200 km) from open marine influences. The alluvial plain was drained by predominantly lowgradient rivers of variable morphology flowing south and southwest, either directly or via numerous crevasse-splays which built out into fresh-to brackish-, shallow-water (b20 m deep) interdistributary lakes, as small delta systems (Fielding, 1984;Haszeldine, 1984;Chen, 1990;Guion et al, 1995;Fulton and Williams, 1988;Turner and Smith, 1995;O'Mara, 1995) (Fig. 3).…”