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Calcrete as a source of heterogeneity in Triassic fluvial sandstone aquifers (Otter Sandstone Formation, SW England)

By
Andrew J. Newell
Andrew J. Newell
British Geological Survey
, Maclean Building, Wallingford, Oxfordshiref OX10 8BB, UK a.newell@bgs.ac.uk
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Published:
January 01, 2006

Abstract

Carbonate is not generally considered as a potential source of large-scale heterogeneity in Permo-Triassic sandstone aquifers. This study shows that carbonate, in the form of early diagenetic calcrete, forms an abundant component of the Triassic Otter Sandstone Formation in south Devon. Three types of calcrete are described from the outcrop of this fluvial sandstone dominated aquifer: rhizocretions; calcrete sheets; and calcrete conglomerates. Data obtained from core plugs show that calcrete reduces sandstone permeability to less than 10−15 m2 and porosity to less than 12%. Calcrete can be sufficiently abundant to produce a significant (up to 30%) reduction in the total effective porosity of the aquifer. Moreover, calcrete conglomerates can form laterally extensive (up to 1 km) low-permeability sheets that will represent major baffles to vertical flow.

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Geological Society, London, Special Publications

Fluid Flow and Solute Movement in Sandstones: The Onshore UK Permo-Triassic Red Bed Sequence

R. D. Barker
R. D. Barker
The University of Birmingham, UK
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J. H. Tellam
J. H. Tellam
The University of Birmingham, UK
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Geological Society of London
Volume
263
ISBN electronic:
9781862395114
Publication date:
January 01, 2006

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