3D characterisation of the Yorkshire Wolds chalk aquifer, UK

The Yorkshire Wolds Chalk aquifer, provides the main source of water supply in East Yorkshire and the city of Hull, which have a population over 900.000. Its structural configuration, including the effects of faulting, influence groundwater flow across the region. However, stratigraphic and structural characterisation is challenging due to limited bedrock being exposed at surface, with most of its extension covered by Quaternary glacial deposits and arable fields and pastures. While the coastal sections have been well characterised through the years, inland areas of the Yorkshire Wolds Chalk aquifer have not been systematically mapped since the late 19th century. The available maps do not reflect present-day stratigraphic divisions or current tectonic understanding, leading to an underestimation of the structural complexity of the aquifer.

A multi-faceted approach to geological mapping is being undertaken in the region by the British Geological Survey, in collaboration with the Environment Agency and Yorkshire Water, integrating remote sensing, targeted field mapping, palaeontological analysis, 2D onshore seismic interpretation and borehole records. The objective of the project is to deliver an up-to-date geological map and structural model of the Chalk bedrock and Quaternary deposits which will impact on the groundwater resources management.

The recent mapping campaigns have led to identifying and characterising numerous new faults in different structural trends, which were not present on previous maps. It has also led to a significant shifting of stratigraphic contacts and formation thicknesses, which have more lateral variability than previously thought. We present some of the most recent updates on the Yorkshire Wolds Chalk aquifer map, which highlight the importance of revising old cartography using modern tectonic and stratigraphic concepts and a multidisciplinary approach to field data collection and compilation. We are also interested in discussing with the hydrogeologist community how to better capture and represent structural complexity around fault zones, so it has an impact on hydrogeological modelling.