Tadcaster Magnesian Limestone 3-D borehole interpretation and cross-sections study

This report was prepared under contract to the Environment Agency and describes the geology of the area surrounding Tadcaster in North Yorkshire. The work was commissioned to investigate the local geology and construct 3-D cross-sections from borehole and surface information. Approximately 1200 boreholes were utilised for the work and these ranged in depth from a few metres to 350m. Five cross-sections were constructed; three WSW-ENE trending sections and two NNW-SSE trending sections all to a depth of 250m below OD. In addition, a series of thematic maps were generated from the lithological component of the digital borehole data. Total superficial aquifer and superficial aquitard maps show how the lithological nature of the superficial sequence varies across the area. Rockhead elevation and superficial thickness maps indicate where the bedrock aquifers outcrop or are near to the ground surface. The east side of the Vale of York in the vicinity of Tadcaster is underlain by a sequence of Permian and Triassic rocks overlain in part by thick superficial deposits dating mainly from the last Ice-Age. The Permian rocks comprise two magnesian limestone aquifers separated by sequences of gypsum/anhydrite and gypsiferous mudstones. The overlying Triassic rocks comprise the major Sherwood Sandstone aquifer. The western part of the area consists of mainly exposed bedrock (Permian dolostone and dolomitic limestone), but the eastern side where the Sherwood Sandstone Group is present has a thick cover of superficial deposits including moraines, glacial lake deposits and alluvial deposits.