The identification of syn-depositionally-active structures in the coal-bearing Upper Carboniferous of Great Britain

Abstract

The Upper Carboniferous coalfields of Great Britain occupy various tectonic settings. Excellent data sets allow detailed analysis of any relationship between structure and the depositional patterns. Syn-depositional movement can be identified on a basin scale, and also at the scale of individual faults. However, with the exception of the Scottish Midland Valley, definitive evidence for syn-depositional movement on specific structures is relatively rare, and especially so in the English Pennine Basin. In particular, there is a general scarcity of detailed structural control on coal-depositional patterns. The environments in which coals formed would have been much more sensitive to subtle ground movements than the higher energy environments of the major channel belts. The precursor peats were widespread and commonly diachronous, and probably spanned around half the available time and space during Westphalian deposition across the Pennine Basin. The rarity of localized structural controls on coal patterns is therefore firm evidence of rarity of specific syn-depositional faulting throughout the sedimentary volume. Using mining data mainly from the Pennine Basin and the Midland Valley, this account discusses examples of likely, and less likely syn-depositional features, and proposes structural and sedimentological critieria for systematic assessment.Much of the British Silesian (Upper Carboniferous) is coalbearing, particularly the strata of mid-A to mid-C Westphalian age. Significant earlier coals are present in Dinantian and Namurian successions in northern Britain, while Westphalian D coals are widespread within the coalfields of southern England and South Wales (Fig. 1). The main sequences have been extensively explored and mined, and many publications describe the regional geology, structural setting, and sedimentology. However, there is little published on syn-depositional movements and associated structures, and the existing literature does not assess the prevalence, or rarity, of movement and its effects on deposition; naturally, authors have reported examples of likely movement, rather than its absence.

Time, hydrologic landscape and the long-term storage of peatland carbon in sedimentary basins

“…The inevitability of such mass movement has been noted and observed in specific blanket bog settings (Tallis, 1985), however, it is not generally considered as a limiting process in all settings in which accommodation space is limited or unavailable. The surface of the peat body may also wrinkle, as proposed by Pearsall (1956) and observed in one mechanical simulation (Briggs et al, 2007), possibly into the characteristic patterns of hummocks and hollows observed in the field (Morris et al, 2013;Pearsall, 1956) and in some coal seams (Broadhurst & Simpson, 1983;Rippon, 1998). Such wrinkles could conceivably generate water channels leading to erosion, drainage and oxidation of a raised peatland under sustained wet conditions.…”

Time, Hydrologic Landscape, and the Long‐Term Storage of Peatland Carbon in Sedimentary Basins

“…The inevitability of such mass movement has been noted and observed in specific blanket bog settings (Tallis, 1985), however, it is not generally considered as a limiting process in all settings in which accommodation space is limited or unavailable. The surface of the peat body may also wrinkle, as proposed by Pearsall (1956) and observed in one mechanical simulation (Briggs et al., 2007), possibly into the characteristic patterns of hummocks and hollows observed in the field (Morris et al., 2013; Pearsall, 1956) and in some coal seams (Broadhurst & Simpson, 1983; Rippon, 1998). Such wrinkles could conceivably generate water channels leading to erosion, drainage and oxidation of a raised peatland under sustained wet conditions.…”