Sedimentary and diagenetic environments of the Wildmoor Sandstone Formation (UK): implications for groundwater and contaminant transport, and sand production

Abstract

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.

Towards prediction of saturated-zone pollutant movement in groundwaters in fractured permeable-matrix aquifers: the case of the UK Permo-Triassic sandstones

“…Laboratory measurements indicate that the seams typically have permeabilities of 3-6 orders of magnitude lower than the host sandstone (Fowles & Burley 1994;Ballard 2000;Main et al 2001;Bouch et al 2006). Fowles & Burley (1994) also found that the permeability of the sandstone immediately surrounding the seams is increased (by 3-4 times in the case described).…”

“…Not surprisingly, granulation-seam orientations may parallel main slip-surface orientations (e.g. Bouch et al 2006) (Table 3). Reactivation is common, and complex structures can form (Edwards et al 1993).…”

“…(Bunch (2006); see also Bunch et al (2004)). also have significantly lower permeability than the majority of the sequence (Bouch et al 2006;. Rushton & Salmon (1993) demonstrated the importance of low-permeability beds, especially mudstones, in controlling vertical head gradients in the sandstones.…”

“…In strong contrast to the practice in petroleum geology, such geologically oriented conceptualizations have seldom been applied in water resources and non-nuclear pollution studies in the UK Permo-Triassic sandstones (but compare Bloomfield et al 2006 andBouch et al 2006).…”

Architectural analysis of a Triassic fluvial system: The Sherwood Sandstone of the East Midlands Shelf, UK

“…However, no calcified root structures or features indicating pedogenesis such rooting are observed at Styrrup, although calcification and evidence of colonization has been described elsewhere in the Sherwood Sandstone (e.g. Bouch et al, 2006;.…”