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.

The Warwickshire Thick Coal is of Westphalian B age, and it developed at the southern margin of the Pennine Basin in central England. It usually consists of three to five leaves of coal which can total up to 8.5 m in thickness. Palynological analysis of the leaves has revealed the presence of four miospore types which occur in similar successions in each leaf. These coals are interpreted as long-residence histosols. Comparable successions have been recognized by other authors and a variety of mechanisms advanced for their formation. The model proposed to account for their origin is change in vegetation due to variations in water table (hydroseral growth), which occur during the development of ombrotrophic bogs similar to those found in the Far East. Many inter-related factors are believed to affect water table variation including climate, topography and raising of the bog surface (the latter controlled by both differential rate of subsidence and accumulation of plant debris). It is probable that the model proposed may be applicable to other coal seams, and this has implications for coal exploration. Estimation of regional rates of subsidence may help in the location of thick long-residence histosols, and examination of miospore cycles within leaves of coal may be useful in predicting the proximity of seam splits.

A discrete fracture network model has been applied to increase the probability of sinking a successful groundwater production borehole at a well-field in Carboniferous rocks in southwest Ireland. The model employs the FracMan software to explicitly represent fractures. Model construction is based on a synthesis of data from a variety of geological and hydrogeological sources. The model is verified and calibrated against borehole measurements and multiborehole pumping tests. The process of model construction indicates that the intensity of flowing fractures is controlled primarily by fracture zones running through the well-field, and that there is also a relationship between flowing fractures and zones of weathered dolomite. Simulations allow the optimal orientation of any production borehole to be determined, and suggest that the most favourable orientation increases the mean number of flowing fractures intersected by up to 30%. The likely yield for different borehole locations can be assessed by conducting flow simulations. Within fracture zones, the probability of a successful production well is high. Flow simulations are also used to quantify the degree of hydraulic interference between boreholes. The results of the modelling can be used to assess the most significant uncertainties and develop a programme of future site characterization that addresses them. JONES, M. A., PRINGLE, A. B., FULTON, I. M. & O'NEILL, S. 1999. Discrete fracture network modelling applied to groundwater resource exploitation in southwest Ireland.

The opencast coal industry seeks to identify and extract near-surface coal reserves. Within the UK Pennine Basin, most coal deposits suitable for opencast exploitation range from middle Westphalian A to lower Westphalian C in age. These deposits dominantly accumulated in an upper delta plain setting in which subsidence rates and depositional setting formed the primary controls on the initial distribution, thickness and quality of coal reserves. Hence an appreciation and analysis of the sedimentary setting and controls on sedimentation are important in the delineation of potential areas of thick, persistent coals. The calculations of in situ coal reserves and coal to overburden ratios are important objectives during exploration for prospective opencast coal sites. Coal reserves are detrimentally affected by early, depositionally related factors such as as wash-outs, seam splits, channel bank collapse and compaction faults. The thickness and type of interseam sedimentary rock (overburden) is directly related to the original despositional environment and the nature of the overburden can change substantially across the working area of an opencast site, reflecting sedimentary facies variations. The various sedimentary facies have unique characteristics and adversely influence mining in a variety of ways, including highwall stability problems, seam gradient changes, groundwater problems, interseam interval variations and facies-specific discontinuities. Many of these problems are related to the presence of palaeochannels. Palaeochannels occur at different scales and contain a variety of fills, and their identification is an important aspect of site exploration. Sedimentary facies mapping, incorporating facies analysis, the construction of isopach maps and palaeocurrent studies can play an important part in an opencast exploration programme. Facies maps have many applications which may be invaluable in site planning, including the delineation of areas of sedimentary disturbance, improved understanding of seam thickness and quality variations, and changes in the interseam strata.