Chalk/Kellaways, Oxford Clay and Osgodby formations separation map

Area where aquifer and shale/clay are present	North Yorkshire Around the Humber and Lincolnshire Norfolk and Cambridgeshire Bedfordshire to Dorset Around the Weald 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	North Yorkshire: 150 to 300 m Around the Humber and Lincolnshire: up to about 450 m, generally increasing south-eastwards Norfolk and Cambridgeshire: 30 to 250 m decreasing south and eastwards Bedfordshire to Dorset; around the Weald: 30 to 1500 m; thickest adjacent to the Weald and south-eastwards on the Isle of Wight
Lithology of intervening strata	North Yorkshire: permeable Corallian Group (principal aquifer); low permeability Kimmeridge Clay Formation (clay); low permeablitiy Ampthill Clay Formation (clay); low permeability Speeton Clay Formation; mixed permeability Lower Cretaceous sedimentary rocks Around the Humber and Lincolnshire: low permeability Kimmeridge Clay Formation (clay); Ampthill Clay Formation (clay); permeable Spilsby Sandstone Formation (principal aquifer); permeable Wealden Group sandstone; low permeability Wealden Group limestone; permeable Lower Greensand Group (principal aquifer) Norfolk and Cambridgeshire: low permeability Kimmeridge Clay Formation (clay); Ampthill Clay Formation (clay); permeable Wealden Group sandstone; permeable Lower Greensand Group (principal aquifer); mixed permeability Gault Formtion (clay); Upper Greensand Formation Bedfordshire to Dorset and around the Weald: permeable Corallian Group (principal aquifer); low permeability West Walton Formation (clay); low permeability Kimmeridge Clay Formation (clay); low permeability Ampthill Clay Formation (clay); permeable Portland Group; permeable Purbeck Group; low permeability Wealden Group; Lower Greensand Group (principal aquifer); mixed permeability Upper Greensand Formation; Gault Formation (clay)
Other major aquifers in the area	North Yorkshire: Triassic sandstone; Magnesian limestone (both below) Around the Humber and Lincolnshire: Oolites; Triassic sandstone; Magnesian limestone; Carboniferous limestone (all below) Norfolk and Cambridgeshire: Crag; Oolites; Permian sandstone; Triassic sandstone; Carboniferous limestone (all below) Bedfordshire to Dorset; around the Weald: Oolites; Permian sandstone; Triassic sandstone; Carboniferous limestone (all below)
Other shales or clays in the area	North Yorkshire: Lias Group; Bowland High Group; Craven Group (all below) Around the Humber and Lincolnshire; Norfolk to Cambridgeshire; Bedfordshire to Dorset; around the Weald: Lias Group (below)
Aquifer map	Chalk principal aquifer
Shale/clay map	Kellaways, Oxford Clay and Osgodby formations shale/clay unit

ch-koo — Chalk/Kellaways, Oxford Clay and Osgodby formations separation map. BGS © UKRI.

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