This is a booklet written to describe the surface and subsurface geology of a 1:50 000 scale geological map. It also includes all of the local details and all other written reports relating to the sheet, for example biostratigraphy, aspects of the engineering geology, and petrography. Sheet descriptions and Sheet explanations are gradually being introduced in place of memoirs. Sheet explanations give a concise account of a geological sheet district in the form of an A5 sized booklet. Many are available in a pack with the accompanying map. Sheet descriptions contain additional, more detailed information and are produced as print-on-demand (POD) A4 reports or on CD.