Chalk/Bowland Shale Formation and Craven Group separation map

Area where aquifer and shale/clay are present	Yorkshire Lincolnshire Note that, for the purposes of drafting this separation map the maximum depth of the Chalk aquifer is taken to be 400 mbgl based on the recommendations in the UK TAG report. More information about this can be found in the methods section
Thickness of intervening strata	About 2000 to 3500 m.
	North Yorkshire: mixed permeability Millstone Grit Group and Pennine Coal Measures Group (mudstones, siltstones and sandstones); permeable Magnesian limestone (principal aquifer); permeable Triassic sandstone (principal aquifer); low permeability Mercia Mudstone Group; low permeability Lias Group (clay); permeable Ravenscar Group; low permeability Oxford Clay Formation (clay); low permeability Osgodby Formation (clay); permeable Corallian Group (principal aquifer); low permeability Kimmeridge Clay Formation (clay); low permeability Ampthill Clay Formation (clay); low permeability Speeton Clay Formation (clay); mixed permeability Lower Cretaceous sedimentary rocks East Yorkshire: mixed permeability Millstone Grit Group and Pennine Coal Measures Group (mudstones, siltstones and sandstones); permeable Magnesian limestone (principal aquifer); permeable Triassic sandstone (principal aquifer); low permeability Mercia Mudstone Group; low permeability Lias Group (clay); mixed permeability Lower Cretaceous sedimentary rocks Around the Humber and Lincolnshire: mixed permeability Millstone Grit Group and Pennine Coal Measures Group (mudstones, siltstones and sandstones); permeable Magnesian limestone (principal aquifer) permeable Triassic sandstone (principal aquifer); low permeability Mercia Mudstone Group; low permeability Lias Group (clay); permeable Great Oolite Group and Inferior Oolite Group (principal aquifer); low permeability Kellaways Formation (clay); low permeability Oxford Clay Formation (clay); low permeability Kimmeridge Clay Formation (clay); Ampthill Clay Formation (clay); permeable Spilsby Sandstone Formation (principal aquifer); permeable Lower Cretaceous sandstone; low permeability Wealden Group limestone; Lower Greensand Group (principal aquifer)
Other major aquifers in the area	Central Lincolnshire: Carboniferous limestone (below)
Other shales or clays in the area	None
Aquifer map	Chalk principal aquifer
Shale/clay map	Bowland and Craven groups shale/clay unit

ch-bcg — Chalk/Bowland and Craven groups separation map. BGS © UKRI.

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