Dedicated to the memory of William T. Holser, colleague and friend. A gap in the fossil record of coals and coral reefs during the Early Triassic follows the greatest of mass extinctions at the Permian-Triassic boundary. Catastrophic methane outbursts during terminal Permian global mass extinction are indicated by organic carbon isotopic (δ 13 C org) values of less than –37‰, and preferential sequestration of 13 C-depleted carbon at high latitudes and on land, relative to low latitudes and deep ocean. Methane outbursts massive enough to account for observed carbon isotopic anomalies require unusually efficient release from thermal alteration of coal measures or from methane-bearing permafrost or marine methane-hydrate reservoirs due to bolide impact, volcanic eruption, submarine landslides, or global warming. The terminal Permian carbon isotopic anomaly has been regarded as a consequence of mass extinction, but atmospheric injections of methane and its oxidation to carbon dioxide could have been a cause of extinction for animals, plants, coral reefs and peat swamps, killing by hypoxia, hypercapnia, acidosis, and pulmonary edema. Extinction by hydrocarbon pollution of the atmosphere is compatible with many details of the marine and terrestrial fossil records, and with observed marine and nonmarine facies changes. Multiple methane releases explain not only erratic early Triassic carbon isotopic values, but also protracted (∼6 m.y.) global suppression of coral reefs and peat swamps.

Abstract Knowledge of subsurface stresses is critical to management and prediction of fluid behaviour in the Earth's crust. However, uncertainties associated with the estimation of vertical stress magnitudes are rarely explored. In settings where the principal stresses are close, small changes of only a few MPa can have drastic effects on, stress regime prediction, fault reactivation and expected fracture behaviour. Using petroleum datasets from the Moomba Gas Field in the Cooper Basin, Australia, we assess the effects of interpolation between gaps in density wireline logs that have been filtered to remove sections of poor density tool contact in coal-bearing sequences. In addition, we compare the sonic velocity–density Nafe–Drake and Gardner transforms by comparing estimates of density from sonic velocity against density from wireline logs. The results indicate that vertical stress could be underestimated by c. 3 MPa at c. 3 km in well Moomba 61, using traditional methods. The Gardner transform shows a stronger correlation between sonic and density values for rocks in the Cooper Basin. However, once calibrated to the regional sonic velocity–density trend, the Nafe–Drake transform better matches the density logging tool in Moomba 61. This study delivers a more robust workflow for estimating the vertical stress in basins with deep coal-bearing strata.

Abstract The Lower and Middle Coal Measures of Langsettian (Westphalian A) and Duckmantian (Westphalian B) age (together equals Bashkirian in part) in Britain comprise an alternation of clastic sediments and coal deposited on coastal and alluvial plains over a period of 2–3.5 million years, depending on which time scale is accepted. In both the Pennine and South Wales Basins there are no obvious unconformities. Many of the clastic sequences show evidence of rapid sedimentation (burial of trees, bivalve escape burrows) that may suggest that a significant amount of time is taken up during the peat-forming intervals. Thickness data from a range of boreholes that record continuous sections through this time period were collated. Coal and sediment thicknesses, as well as coal to sediment ratios, are compared both within and across the basins. Data on the coals has allowed consideration of the time taken to deposit the peats. This work considers the compaction of the peat to coal, as well as a range of peat accumulation rates. Assuming the largest de-compaction rates and slowest accumulation rates of the coal formation, less than 50% of the allocated time can be accounted for. In addition however, calculations suggest that peat formation accounts for less than 25% of the total time taken for sediment accumulation. It is suspected that there are major time gaps in the sequences, most probably occurring between seat-earths and coal and within the coals, and it is believed that this finding has significance for the debate over short-term climate changes in the Carboniferous and the causes of peat and sediment alternations. Supplementary material: Borehole thickness data and references are available at http://www.geolsoc.org.uk/SUP18788

Abstract Depositional environments of coal beds, despite the voluminous works on this topic, remain elusive and difficult to prove (Dapples and Hopkins, 1969; Ferm et al., 1979; Rahmani and Flores, 1984; Lyons and Alpern, 1989; McCabe and Parrish, 1992). Factors that control coal accumulation are as varied as the many disciplines (sedimentol- ogy, coal petrology, geochemistry, paleobotany, etc.) studying the origin of coal beds. For decades, approaches to coal-bed depositional environments have been dichoto- mous; that is, separate and independent analyses of the organic deposits and “accompanying” sediments. This uni- discipline-research approach has fragmented and confused efforts to understand this century-old problem (Schaler, 1885; Stevenson, 1910). However, attempts to bridge the interdisciplinary gap during the past few decades have produced new insights on the nature and origin of coals and associated sedimentary rocks (Raistrick and Marshall, 1939; Styan and Bustin, 1983; Pocknall and Flores, 1987; Stanton et al., 1989; McCabe, 1991; Diessel, 1992). The economic potential of coal-bed methane gas resource has renewed study of coal resources, coal rank, coal geochemistry, and physical properties of coals (Rightmire et al., 1984; Fassett, 1988; Coalbed Methane Symposium, 1989). Although coal beds often serve as source and reservoir rocks of methane gas, it has been found that adjoining sandstones can also serve as reservoir rocks (Rice and Flores, 1990; Flores et al., 1991; Law et al., 1991; Pashin et al., 1991). Thus, knowledge of the origin and properties of the sedimentary rocks lateral to, above, and below coal beds is vital to a successful

Abstract For the west European regional chronostratigraphic framework, the Cantabrian substage was conceived as covering a widely apparent stratigraphic gap between the top of the Westphalian and the base of Stephanian A, the lowest unit of the Stephanian. A continuous depositional history covers this time gap in the Cantabrian region of Spain; the upper limit of this interval was defined by the succeeding Barruelian substage, equivalent to Stephanian A. Intense tectonic and magmatic activity characterizes this period; the Iberian orogenic belt was an essentially linear feature buckled through the Late Pennsylvanian into the tightly folded Cantabrian Orocline. This evidences an extensive southern foreland to the Variscides, in which the coal-swamp biome persisted through the Late Pennsylvanian, supporting biostratigraphical correlation with the Donbass. New high precision U–Pb CA-ID-TIMS radiometric dating of tonstein horizons supports a preliminary time-framework of regional substages: base of the Asturian (proposed, ex-Westphalian D) c. 310.7 Ma; base of the Cantabrian c. 307.5 Ma; base of the Barruelian (ex-Stephanian A) c. 304.9 Ma; base of the Saberian (proposed) c. 303.5 Ma. The Cantabrian and Barruelian embrace the entire Kasimovian of the global time-scale, and the top of the Barruelian is essentially coincident with the base of the Gzhelian.

Abstract Coal has been mined in the South Wales Coalfield for centuries. Substantial dewatering operations have attended these activities, particularly with the advent of steam and electric pumps that facilitated deeper mining operations. However, underground coal mining in South Wales has been in decline since 1913. The closure of the last deep mine in the eastern part of the coalfield in 1992 entailed a cessation of pumping over a large geographical area, with a resultant recovery of the groundwater. A consequence of this recovery is that emissions of mine water are occurring at the surface. Surface water emissions of known provenance from the Upper Coal Measures were sampled in 2000 and characterized in terms of their major ion composition. Also, known emissions of mine water within the catchments of the Rivers Ebbw, Ebbw Fach, Rhymney and Taff Bargoed were sampled, and the major ion data plotted on trilinear Piper diagrams. The results indicate that two distinctive hydrochemical facies could be identified from these plots. By combining knowledge of the underground mine workings and lithology, and by comparison with the Upper Coal Measures ‘fingerprint’, it is possible to divide the mine water emissions into those sourced from the Upper and Middle and Lower Coal Measures, and at times to infer a degree of mixing between the two. The conclusion is that in the eastern valleys of the South Wales Coalfield, the Upper Coal Measures water has a calcium-sulphate facies and the Middle and Lower Coal Measures water has a sodium-sulphate to sodium-bicarbonate facies. This information can be added to the available knowledge to aid in assessing the nature and the progress of groundwater recovery within the coalfield. This paper refers to preliminary work that has been carried out in the South Wales Coalfield to attempt to ‘fingerprint’ mine water emissions to identify their underground source. This, in turn, provides valuable information on the hydrogeological regime and, coupled with the geological and mining setting, may further assist in identifying underground flow paths. This information helps to fill in some of the ‘knowledge gaps’ and provide a tool for use in the prediction of future surface mine water emissions and in the formulation of treatment-mitigation strategies. The current work uses observations and interpretations of the hydrochemistry of the coal Measures to develop a robust and simple to use method of characterizing and classifying mine water emissions within the South Wales Coalfield. It is anticipated that a similar interpretive process could be applied to mine water emissions in other coalfields, although it should be stressed that this cannot be considered as a ‘stand alone’ process and that the initial characterization of the mine water needs to be carried out with reference to the geological and mining setting for any particular area under consideration.