An in Depth Look at the Superficial Deposits in the Selby Area And

Expert | Impartial | Innovative An in depth look at the superﬁcial deposits in the Selby area and implications for the groundwater system

Burke, H. F., Ford, J. R., Hughes, L., Thorpe, S., and Lee, J. R. (British Geological Survey)

Introducon The Environment Agency’s regional groundwater model of the Selby area of northern England does not convey the complexity and variable hydrogeological properes of the superficial deposits. To address this the Environment Agency commissioned a 3D geological model of the superficial deposits from Thorne near Doncaster to Haxby just north of York. Covering an area of 1,300km2, the model comprises 22 superficial units, plus arficial ground and 6 schemac bedrock units.

Quaternary geology The Quaternary succession of the model area is dominated by glacial sediments laid down in the Late Devensian, the last major glaciaon to aﬀect the United Kingdom. The Escrick Moraine crosses the model area, marking the southern-most extent of the Brish-Irish Ice Sheet during the Late Devensian glaciaon (Ford et al, 2008). York Moraine

South of the Escrick Moraine the Quaternary sediments are dominated by laminated clays, silts and sands of the Hemingbrough Glaciolacustrine Formaon that were laid down by Glacial Lake Humber, a huge pro-glacial lake system. Escrick Moraine North of the Escrick Moraine the Quaternary geology is complex and dominated by the Vale of York Formaon ll sheet. This overrode the Hemingbrough Glaciolacustrine Formaon, deposing ll containing lenses of sand and gravel and laminated clay. Glaciolacustrine clays and silts also overlie the Vale of York ll sheet. Widespread cover sands occur throughout the model R Derwent area, plus ﬂuvial deposits associated with the rivers Aire, Derwent and Ouse. Remnants of an older ll sheet (possibly Middle Pleistocene) occur on higher ground in the west of the model area. R Ouse

R Aire

Vale of York till: composed of sandy BGS GeologyGB 50K superﬁcial gravelly clay with cobbles and geology map of the model area. Inset boulders. Clasts of Carboniferous limestone and sandstone with Upper laminated clay and intervening shows the Devensian (blue) and occasional volcanic material indicate a running sand of the Hemingbrough Anglian (red) glaciaon limits. Includes northern England source area Glaciolacustrine Formation mapping data licensed from Ordnance Survey. © Crown Copyright and/or database right 2019. Licence number 100021290 EUL

Sherwood Sandstone Group bedrock exposed at ground surface

Cover sand: sand with some gravel, laid down by ﬂuvial and aeolian processes. Mobilises during ploughing and certain weather conditions. Peat deposits at Hatﬁeld Moors Remnants of an older till sheet, possibly Mid Pleistocene

Applicaons of the model The Environment Agency is parcularly interested in areas where the underlying Sherwood Sandstone Group aquifer recharges through exposures at the ground surface and areas where permeable superficial deposits form conduits from the ground surface to the aquifer. Key findings The model has increased our scienfic understanding of the Vale of York’s glacial history. For example, the model reveals the extent of the Hemingbrough Glaciolacustrine Formaon beneath the Vale of York ll.

Cross-section EA_Selby_WE5_LJ_NorthWest runs west to east in the north of the model area. Top view coloured according to lithostratigraphy. Bottom view coloured using inferred permeability. Red is weakly permeable, green is highly permeable.

References Burke, H. F., Ford, J. R., Hughes, L., Thorpe, S., and Lee, J. R., 2017. A 3D geological model of the superﬁcial deposits in the Selby area. Brish Geological Survey commissioned report no. CR/17/112N. Available on the NERC Open Research Archive at: hp://nora.nerc.ac.uk/id/eprint/519164/ Cooper, A. H., Ford, J. F., Price, S. J., Hall, M., Burke, H. F. and Kessler, H. K., 2007. The digital approach to understanding the Quaternary evoluon of the Vale of York, UK. Brish Geological Survey poster. hp://nora.nerc.ac.uk/id/eprint/4077/1/Vale_of_York_%285%29.pdf Ford, J. R., Cooper, A. H., Price, S. J., Gibson, A; D., Pharaoh, T. C and Kessler, H., 2008. Geology of the Selby district. A brief explanaon of geological map sheet 71 (Selby). Brish Geological Survey publicaon. Acknowledgements The authors wish to thank the Environment Agency (York oﬃce) for commissioning this work and giving their permission to present this poster.

Contact Information

Helen Burke [email protected] www.bgs.ac.uk