British Coal Measures Research Articles

Untangling the Gordian knot\u2014further resolving the super-species complex of 300-million-year-old xiphosurids by reconstructing their ontogeny

The group Xiphosurida (horseshoe “crabs”) is today only represented by four species. However, in the fossil record, several dozen species have been described, especially from the Carboniferous (about 300 million years ago). Several species have been interpreted as representatives of Euproops or Belinurus, but there is ongoing discussion which of these species are valid and how they can be differentiated. Recent studies suggested that differences in the timing of individual development could provide information for species distinction, exemplified by studies on Euproops danae (Mazon Creek, USA) and Euproops sp. (“Piesproops”; Piesberg, Germany). For this study, we reinvestigated all Carboniferous xiphosurids from the British Coal Measures stored in the collections of the Natural History Museum London. Size comparisons of the specimens revealed nine size groups; the smaller specimens were originally labelled as Belinurus, the larger ones as Euproops. The nine size groups exhibit five different morphotypes differing in structures surrounding the posterior shield (= thoracetron): spines of different lengths and, in larger specimens, a more or less developed flange. Two of these morphotypes show significantly longer spines than the remaining specimens and could be conspecific as E. anthrax. The remaining specimens are interpreted as growth series of another species, presumably of E. rotundatus. An ontogenetic flange formation is also known from E. danae and the “Piesproops”, but the timing differs between all three species. In E. rotundatus, the flange develops rather late, but then comparably abruptly, which makes this development more metamorphic in relation to development in the other species.

The phylogeny of fossil whip spiders

BackgroundArachnids are a highly successful group of land-dwelling arthropods. They are major contributors to modern terrestrial ecosystems, and have a deep evolutionary history. Whip spiders (Arachnida, Amblypygi), are one of the smaller arachnid orders with ca. 190 living species. Here we restudy one of the oldest fossil representatives of the group, Graeophonus anglicus Pocock, 1911 from the Late Carboniferous (Duckmantian, ca. 315 Ma) British Middle Coal Measures of the West Midlands, UK. Using X-ray microtomography, our principal aim was to resolve details of the limbs and mouthparts which would allow us to test whether this fossil belongs in the extant, relict family Paracharontidae; represented today by a single, blind species Paracharon caecus Hansen, 1921.ResultsTomography reveals several novel and significant character states for G. anglicus; most notably in the chelicerae, pedipalps and walking legs. These allowed it to be scored into a phylogenetic analysis together with the recently described Paracharonopsis cambayensis Engel & Grimaldi, 2014 from the Eocene (ca. 52 Ma) Cambay amber, and Kronocharon prendinii Engel & Grimaldi, 2014 from Cretaceous (ca. 99 Ma) Burmese amber. We recovered relationships of the form ((Graeophonus (Paracharonopsis + Paracharon)) + (Charinus (Stygophrynus (Kronocharon (Charon (Musicodamon + Paraphrynus)))))). This tree largely reflects Peter Weygoldt’s 1996 classification with its basic split into Paleoamblypygi and Euamblypygi lineages; we were able to score several of his characters for the first time in fossils. Our analysis draws into question the monophyly of the family Charontidae.ConclusionsOur data suggest that Graeophonus is a crown group amblypygid, and falls within a monophyletic Paleoamblypgi clade, but outside the family Paracharontidae (= Paracharonopsis + Paracharon). Our results also suggest a new placement for the Burmese amber genus Kronocharon, a node further down from its original position. Overall, we offer a broad phylogenetic framework for both the fossil and Recent whip spiders against which future discoveries can be tested.

Hydrochemistry and stable isotopes as tools for understanding the sustainability of minewater geothermal energy production from a ‘standing column’ heat pump system: Markham Colliery, Bolsover, Derbyshire, UK

The abandoned workings of the former Markham Colliery are still in the process of flooding. They are being exploited, via a ‘standing column’ heat pump arrangement in Markham No. 3 shaft, to produce thermal energy. From 2012, water was pumped from 235m below ground level in the shaft at c. 15°C and 2–3l/s, through shell and tube heat exchangers coupled to a 20kW heat pump, to supply space heating to commercial offices. The thermally spent (cool) water was returned to the same shaft at c. 250m bgl at around 12°C. The mine water contained iron, c. 6000mg/l chloride, and was highly reducing. Avoiding contact with oxygen was effective in preventing problems with ochre scaling. In January 2015, taking advantage of rising water levels, the pump was repositioned at 170m bgl, and the reinjection diffuser at 153m bgl. Since then, both iron concentration and salinity have fallen significantly, suggesting stratification in the shaft. Stable isotope data from sampling in 2015 generally show little variation. Sulphate δ34S exhibits values typical for British Coal Measures (c. +5‰), whilst δ18O/δ2H indicate influence of fresh meteoric waters. Chloride and sodium concentrations have gradually increased since May 2015, possibly indicating a renewed influence of deeper, more saline, waters and reflecting the gradual rise of mine water in the shaft. Further monitoring of mine water chemistry and isotopic composition is required to better assess the sustainability of the Markham heat pump scheme and advise on optimal management of this mine water resource.

Two new species of megasporangiate <i>Sigillariostrobus</i> Schimper (Sigillariostrobaceae) fructifications from the British Coal Measures

Abstract. The arborescent lycophyte group known as the sigillarians bore pedunculate fructifications, including Sigillariostrobus Schimper, which has a known propensity to disaggregate, making comparisons of cones and in situ spores often difficult if not impossible. Sigillariostrobus is monosporangiate, containing either megaspores or microspores. Two new species of Sigillariostrobus with megaspores are described from the British Coal Measures. Two cones of Sigillariostrobus saltwellensis sp. nov. are described from Langsettian–Duckmantian strata of Great Britain, containing in situ Laevigatisporites glabratus (Zerndt) Potonié and Kremp spores, making this the first British Sigillariostrobus species described containing such spores. Sigillariostrobus barkeri sp. nov. is given here to the previously described cone with in situ Tuberculatisporites brevispiculus (Schopf) Potonié and Kremp spores. This is the first Sigillariostrobus cone with this megaspore species in situ, and thus shows that T. brevispiculus and T. mamillarius (Bartlett) Potonié and Kremp are not conspecific as others have previously suggested.

A taxonomic revision of orthosternous scorpions from the English Coal-measures aided by X-ray Micro-Tomography (XMT)

Fossil scorpion systematics – particularly that of the diverse assemblage found in Carboniferous Coal Measure deposits – are problematic, being characterised by a large number of frequently monotypic taxa, based on a limited set of characters. These Palaeozoic scorpions have the potential to elucidate the nature of the scorpion stemgroup and hence to inform long running debates regarding the origin of the crown group and relationships between extant lineages. Carboniferous taxa are often found in siderite concretions and can be preserved in three dimensions. This study investigates two such fossils of the species Compsoscorpius buthiformis (Pocock, 1911) with the aid of X-ray Micro-Tomography (XMT) and computer reconstruction. These scans reveal important new details of the anatomy, such as the walking legs, that allow more detailed comparison with coeval taxa. Many of these taxa are revealed here to be junior synonyms of C. buthiformis and previous taxonomic practice, as it relates to Coal Measures scorpions, is criticised. The ecology of C. buthiformis is also reviewed in light of the new evidence from XMT. In particular, aspects of its walking leg and metastomal anatomy are analogous to that of extant lithophilic and ‘errant’ leaf-litter scorpions.

Morphology and systematics of anthracomartidae (Arachnida: Trigonotarbida)

Abstract: X‐ray microtomography (XMT) was applied to three species of the extinct arachnid order Trigonotarbida, hosted in siderite nodules from the late Carboniferous British Middle Coal Measures. All three, Cryptomartus hindi (Pocock, 1911), Cleptomartus plautus (Petrunkevitch, 1949) and Maiocercus celticus (Pocock, 1902), belong to the family Anthracomartidae. As well as providing interactive three‐dimensional visualisations of their likely appearance in life, XMT study has resolved new morphological detail, yielding key data about the likely stance and habitus of these early arachnids. Similarities in the form of the carapace, eyes and coxosternal region between anthracomartids and the Devonian genus PalaeocharinusHirst, 1923 are highlighted. Analogies in limb disposition are drawn between anthracomartids and modern crab spiders (Araneae: Thomisidae), which exhibit sit‐and‐wait style predatory behaviour. Anthracomartids are relatively common fossils at many Coal Measures localities. Although they appear to exhibit limited morphological variation, numerous genera and species have been proposed in the literature, often distinguished from each other on rather trivial characters. From our reconstruction of well‐preserved examples, we have resolved a number of common features likely to be present in a typical anthracomartid. Comparisons to this model suggest that the characters on which many anthracomartid genera are distinguished may be artefacts of preservation. We hence treat PromygaleFrič, 1901, BrachylycosaFrič, 1904, PerneriaFrič, 1904, CoryphomartusPetrunkevitch, 1945, CryptomartusPetrunkevitch, 1945, PleomartusPetrunkevitch, 1945, CleptomartusPetrunkevitch, 1949 and OomartusPetrunkevitch, 1953 as junior synonyms of the type genus of the family, AnthracomartusKarsch, 1882. Only the genera BrachypygeWoodward, 1878 and MaiocercusPocock, 1911 are additionally retained. Within Anthracomartus, Cleptomartus planusPetrunkevitch, 1949, Cryptomartus meyeriGuthörl, 1964, Cleptomartus hangardiGuthörl, 1965 and Cryptomartus rebskeiBrauckmann, 1984 are treated as junior synonyms of A. hindiPocock, 1911 (all syn. nov.). Cleptomartus plautusPetrunkevitch, 1949 and Anthracomartus denuitiPruvost, 1922 are treated as junior synonyms of A. priestiPocock, 1911 (both syn. nov.).

Longwall mining-induced fault reactivation and delayed subsidence ground movement in British coalfields

Faults located in areas undergoing mining subsidence during the longwall extraction of coal seams may undergo reactivation. This has been observed and documented throughout the UK (and in other major coalfields around the world) over the past 150 years. Subsidence-induced fault reactivation may cause moderate to severe damage to foundations, houses, buildings, structures and underground services, as well as damage to agricultural land through disruption of drainage and alteration of the gradient. Monitoring of faults, as they are affected by undermining, has resulted in a better understanding of fault reactivation mechanisms and of the various styles of fault reactivation, in different geological and mining settings. The duration of fault reaction is difficult to determine because of the lack of observational data. However, trough subsidence following longwall extraction of coal is rapid, often being completed within weeks to months. This is commonly followed, shortly afterwards, by a period of delayed subsidence known as residual subsidence, which in the British Coal Measures rarely accounts for more than 10% of the total subsidence. In many circumstances, where faults are not present, residual subsidence is complete within 4 months, although several cases have been recorded where subsidence effects were still being observed more than 2 years after mining had finished. Generally, it is accepted that fault reactivation sometimes may extend over the period of residual subsidence. In parts of the abandoned or partially active coalfields in the UK, relatively smaller ground movements have been observed in the vicinity of fault outcrops many years after mining has ceased. The reasons for this are not fully understood. None the less, prolonged periods of fault reactivation may have an important effect on land use and construction. The objectives of this paper are to consider fault reactivation and, in particular, to document examples of post-mining ground movements around fault outcrops and to discuss possible causal mechanisms. Features associated with these movements include increases in elevation of the ground surface and deformation (e.g. subsidence, grabens, scarps or steps, fissures, compression and tension) of the ground surface in the vicinity of faults. These features, in turn, may be associated with groundwater or mine water rebound.

New Euthycarcinoids and an Enigmatic Arthropod from the British Coal Measures

Two new species of euthycarcinoids (Arthropoda), Kottixerxes anglicus sp. nov. and Smithixerxes pustulosus sp. nov., are described from the Coal Measures of Westhoughton, Lancashire and Coseley, West Midlands (Westphalian A and B respectively). Both genera are previously known from Mazon Creek, USA (Westphalian D). An additional, enigmatic arthropod with possible euthycarcinoid affinities, Arthrogyrinus platyurus gen. et sp. nov., is described from Coseley. Hypotheses concerning the phylogenetic position of euthycarcinoids are critically reviewed.

Cordaites tree‐trunks in the British Coal Measures

Carboniferous cordaitean tree‐trunks have been discovered in Britain for the first time.

Sphenacanthus, a Palaeozoic freshwater shark

Recently discovered material from the Viséan Oil Shale Groups of the Scottish Midland Valley allows a description of the anatomy of the head and dermal skeleton ofSphenacanthus serrulatusto be made for the first time. This suggests that it was a typical phalacanthous shark, rather larger, but otherwise quite similar to the contemporaneousTristychius arcuatus. Like the latter, it appears to have had a long otic region on the neurocranium, a heterodont dentition and two dorsal finspines, but it differed in having longer, deeper jaws and a complete covering of scales (aggregated lepidomoria).Sphenacanthus serrulatusis absent from the British Coal Measures (Westphalian), but the very similarSphenacanthus hybodoidesis found here. Both these forms appear to be normal components of the freshwater «lagoonal» stage of the cyclothems and provide further evidence that Palaeozoic sharks were more varied in their choice of habitat than those of today.

Sphenacanthus, a Palaeozoic freshwater shark

Abstract Recently discovered material from the Visean Oil Shale Groups of the Scottish Midland Valley allows a description of the anatomy of the head and dermal skeleton of Sphenacanthus serrulatus to be made for the first time. This suggests that it was a typical phalacanthous shark, rather larger, but otherwise quite similar to the contemporaneous Tristychius arcuatus . Like the latter, it appears to have had a long otic region on the neurocranium, a heterodont dentition and two dorsal finspines, but it differed in having longer, deeper jaws and a complete covering of scales (aggregated lepidomoria). Sphenacanthus serrulatus is absent from the British Coal Measures (Westphalian), but the very similar Sphenacanthus hybodoides is found here. Both these forms appear to be normal components of the freshwater «lagoonal» stage of the cyclothems and provide further evidence that Palaeozoic sharks were more varied in their choice of habitat than those of today.

Transmission‐reflection tomography: Application to reverse VSP data

A multiphase tomographic algorithm is presented that allows 2-D and 3-D slowness (inverse of velocity) and variable reflector depth to be reconstructed simultaneously from both transmission and reflection traveltimes. We analyze the ambiguity in the determination of velocity and depth in transmission and reflection data and realize that depth perturbation is more sensitive to reflection traveltime anomalies than slowness perturbation, whereas the reverse is true of transmission traveltime anomalies. Because of the constraints on velocity and depth provided by the different wave types, this algorithm reduces the ambiguity substantially between velocity and depth prevalent in reflection tomography and also avoids the undetermined problem in transmission tomography. The linearized inversion was undertaken iteratively by decoupling velocity parameters from reflector depths. A rapid 2-D and 3-D ray‐tracing algorithm is used to compute transmission and reflection traveltimes and partial derivatives with respect to slowness and reflector depth. Both depth and velocity are parameterized in terms of cubic B‐spline functions. Synthetic examples indicate the improvement in tomographic results when both transmission and reflection times are included. The method has been applied to a reverse vertical seismic profile (VSP) data set recorded on the British coal measures along a crossed‐linear array. Traveltimes were picked automatically by the simultaneous determination of time delays and stacking weights using a waveform matching technique. The tomographic inversion of the observed reverse VSP images two fault‐zones of lower velocity than the surrounding media. The location of the faults was confirmed by near‐by reflection lines. The technique can be applied to offset VSPs or reverse VSPs and coincident VSP and surface reflection data.

A geotechnical survey of some British Coal Measures mudstones, with particular emphasis on durability

Samples of fresh mudstones were obtained from near Tow Law and Kirkheaton, and of weathered mudstones from near Wrexham. The mineral composition of these mudstones was similar, kaolinite being the principal clay mineral, the clay mineral fraction dominating. Quartz was the chief non-clay mineral present. Some basic geotechnical and index properties were determined. The fresh mudstones from near Tow Law had a low plasticity, as did the moderately and highly weathered mudstones from near Wrexham. However, the completely weathered mudstones from the latter area possessed intermediate plasticity. The strength of the fresh mudstones from near Kirkheaton was notably higher than that of the mudstones from near Tow Law. Both groups of fresh mudstones displayed significant anisotropy ratios when they underwent axial and diametral point load testing. This, no doubt, was due to the influence of lamination. As durability is one of the most important engineering properties of mudstone, it was assessed by a number of tests. One cycle slake durability testing did not appear to offer an acceptable indication of the durability of mudstones when compared with cyclic wetting and drying, cyclic freezing and thawing, and geodurability classification. Cyclic slake durability testing and comparison with unconfined compressive strength would seem to be a more reliable way of determining durability. Both fresh and weathered mudstones underwent little expansion when subjected to swelling tests. However, in the case of the weathered mudstones, the amount of swelling stress and strain could be related to basic geotechnical properties.

A method to predict final subsidence basins by means of a finite difference computer code : L. R. Alejano Monge, P. Ramirez Oyanguren & R. De la Fuente, in: Land subsidence, Proc. international symposium, The Hague, 1995, ed F.B.J. Barends & others, (IAHS; Publication, 234), 1995, pp 251–258

In this paper a method to predict subsidence due to total extraction of flat coal seams is presented. The method is based on the adequate characterization and the correct definition of the constitutive model of behaviour of rock masses, and is implemented in a finite difference numerical code. Due to the existence of an enormous quantity of data related to material properties as well as to subsidence measurements in the UK, the method is validated with acceptable results for standard British carboniferous coal measures rock masses.

95/00322 Geological and hydrological controls on the producibility of coalbed methane

British Coal measure their methane emissions at 0.8 ± 0.2 million tonnes from UK coal mining in 1987. However, this figure cannot be verified until British Coal releases relevant data. Recently, the US Environmental Protection Agency has endorsed the use of an emission equation as a means of calculating methane emissions from coal mining. Methane emissions from coal mining rise to 1.19 – 2.21 Mt when this equation is applied to the UK. Both these estimates represent a lost resource and a major global warming effect due to methane's potency as a greenhouse gas.

Absolute stress and stress change measurements in British Coal Measures : Bigby, D N; Cassie, J W; Ledger, A R Proc ISRM Symposium: Eurock'92, Chester, 14–17 September 1992P390–395. Publ London: Thomas Telford, 1992

Absolute stress and stress change measurements in British Coal Measures : Bigby, D N; Cassie, J W; Ledger, A R Proc ISRM Symposium: Eurock'92, Chester, 14–17 September 1992P390–395. Publ London: Thomas Telford, 1992

Coal-bed methane in the UK

British Coal measure their methane emissions at 0.8 ± 0.2 million tonnes from UK coal mining in 1987. However, this figure cannot be verified until British Coal releases relevant data. Recently, the US Environmental Protection Agency has endorsed the use of an emission equation as a means of calculating methane emissions from coal mining. Methane emissions from coal mining rise to 1.19 – 2.21 Mt when this equation is applied to the UK. Both these estimates represent a lost resource and a major global warming effect due to methane's potency as a greenhouse gas.

Dips of normal faults in British Coal Measures and other sedimentary sequences

Fault dip measurements (n = 3291) from 122 faults in British Coalfields are presented. Two classes of normal fault are recognized: (a) gently dipping (<55°) synsedimentary faults of gravity driven or, less commonly, tectonic origin and (b) steeply dipping (>55°) post-coalification tectonic faults formed at depths of about 2.5 km which comprise 90% of the faults analysed. Dip data from the steeply dipping faults are variable (standard deviation = 9°), both on single faults and between faults, and 70° is a better approximation of fault dip than the commonly accepted value of 60°. Data on tectonic normal faults, with comparable depths of formation (<3–4 km), from other sedimentary sequences show that dips of greater than 60° are quite usual. Systematic changes of dip on single fault surfaces have predictable effects on the curvature of fault traces. Using the modified Griffith fracture criterion the dips of faults at varying depths (up to 4 km) are calculated for both unsaturated (dry) and saturated rocks. The dips of normal faults are expected to vary from 90° at the surface to 60° at 3–4 km and this variation is consistent with the limited field data available. The coalfield data are consistent with fault formation at standard hydrostatic pore fluid pressures at depths of about 2.5 km. Below depths of a few kilometres normal faults are expected to flatten out gradually to a dip of 45°, but such flattening is not necessarily an indication of an underlying detachment.

Geological controls on the formation and distribution of gas in British coal measure strata

The methane, ethane, higher alkanes and nitrogen found in British coal seams are residual products of coalification occasionally complemented by petroleum-derived hydrocarbons. Carbon dioxide, a minor constituent of coal seam gas, may have been introduced during the phase of cleat mineralisation following uplift. Helium and argon are considered to be radiogenic in origin. Variations in seam methane content with depth, geographic location and rank can be interpreted in terms of the coalification and erosion history of a coalfield. However, the limitations inherent in an analysis in which coal rank is represented by a single parameter must be recognised. There are indications that the methane content of a seam is not likely to exceed the methane sorption capacity of the coal determined at a temperature commensurate with that obtaining at the maximum burial depth. Research in the East Midlands coalfield suggests that structurally controlled migration of coalification gas was contemporaneous with folding. During the Permo-Carboniferous erosion period gas was lost from outcropping seams. Subsequently, the bulk permeability of the seams must have been reduced, perhaps as a result of cleat mineralisation, because no re-distribution of methane appears to have occurred in response to later (Tertiary) deformation and gas contents of seams at incrop below the base of the Permo-Triassic have remained zero. Data on the effects of faulting on seam gas contents are few but the expectation is that faults, of appropriate age and orientation, whilst inhibiting in-seam migration may, in some instances have aided cross-measures movement of gas. Elevated seam ethane and propane contents are frequently encountered in seams disturbed by oil-bearing faults.

Coal Measures mudrocks: composition, classification and weathering processes

Abstract British Coal Measures mudrocks are dominantly non-marine, mature sediments with a high average clay minerals content of over 75%. A geological classification based on quartz content does not differentiate the dominant durable mudrocks from the non-durable types and overconsolidated clays in the formation. A uniaxial compressive strength greater than 3.6MN/m 2 with a three cycle slake durability value of over 60% is suggested as an appropriate division between durable and non-durable mudrocks of this age. Physical breakdown, which acts as a control on chemical weathering triggered by pyrite oxidation, is considered to be governed by incidence of sedimentary structures, slaking and expandable mixed-layer clay content. Shear strength reduction during post-glacial weathering can be significant. A tentative fully weathered effective stress peak strength for the weakest mudrocks and clays is deduced to be φ′ = 22°( c ′ = 0). Colliery tip investigations indicate that chemical weathering effects on the shear strength of the mudrocks are small. A diagenetic rank factor applies both to peak shear strength and slake durability of mudrocks excavated from UK coal mines.