Sedimentary and diagenetic environments of the Wildmoor Sandstone Formation (UK): implications for groundwater and contaminant transport, and sand production
Published:January 01, 2006
Jon E. Bouch, Ed Hough, Simon J. Kemp, John A. McKervey, Geoffrey M. Williams, Richard B. Greswell, 2006. "Sedimentary and diagenetic environments of the Wildmoor Sandstone Formation (UK): implications for groundwater and contaminant transport, and sand production", Fluid Flow and Solute Movement in Sandstones: The Onshore UK Permo-Triassic Red Bed Sequence, R. D. Barker, J. H. Tellam
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The Wildmoor Sandstone Formation, proved in three boreholes drilled at Birmingham University, is dominated by fine- to medium-grained sandstones deposited in a braided river environment, within which channel lag, channel fill and abandoned channel facies are recognized. Minor proportions of aeolian sandsheet are present, as are dolocretes, not previously reported in the formation.
The sandstones are feldspathic and lithic arenites, and typically are clay-poor. Early dolomite dominates the diagenetic overprint, and is preferentially developed in channellag deposits. Burial diagenetic effects are minor. Late calcite occurs as a pore-filling phase and within fractures.
Minor fractures and granulation seams are oriented parallel to the NE–SW Birmingham Fault. ‘Conventional’ granulation seams, with comminution of detrital material, and more complex seams containing comminuted dolomite cement with a millimetre-wide halo of dolomite cement are present, the latter implying that the sandstone was dolomitecemented at the time of fracturing.
Several scales of heterogeneity will affect groundwater solute transport. The palaeosols and abandoned channel mudstones may act as barriers to vertical flow at the decimetre scale. Dolomite-cemented channel-lag deposits may act similarly at smaller scales. Granulation seams have permeabilities of two–three orders of magnitude lower than their host sandstones, but their limited occurrence may limit their impact on larger scale flow. Matrix permeability is controlled by grain size and dolomite cement.
The fines in the fine-grained, ripple cross-laminatied sandstones were extensively washed out during coring, and this lithology may be a source of sand yields in some sandstone boreholes. Although no enhancement of particle yields was seen during packer testing, the possibility remains that more comprehensive failure may occur at higher pumping rates.
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Fluid Flow and Solute Movement in Sandstones: The Onshore UK Permo-Triassic Red Bed Sequence
Sandstone aquifers are common worldwide: they contain a significant proportion of the Earth’s fresh water supplies. However, because of their textural complexity and the frequent occurrence of both matrix and fracture flow, prediction of flow and pollutant migration is still a considerable challenge. This volume contains a collection of papers summarizing current research on an example sandstone aquifer: the UK Permo-Triassic Sandstone sequence. These red bed, organic-poor sandstones are of fluvial and aeolian origin, are often strongly textured, and are cut by discontinuities of a wide range of permeabilities. Matrix flow often dominates, but fracture flow also occurs. The papers in the volume deal with research on saturated and unsaturated flow, and solute and non-aqueous-phase liquid movement. They cover investigations from laboratory to regional scale, and involve a wide range of approaches, from petrophysical through geophysical and hydrochemical to modelling.
The book is intended to be of interest to researchers and practitioners involved in water resources and groundwater pollution, and to hydrogeology, water engineering, and environmental science students.