I have benefited from many fruitful discussions with fellow geologists at this site, including Charles Copp, Elizabeth Devon, Andy Farrant, Jim Hanwell, Peter Hardy, Kevin Isaac, Chris King, Hugh Prudden, Rick Ramsdale, John Reynolds, Dorothy Satterfield and Roger Suthren. Their opinions have influenced me to a greater or lesser extent, but the interpretations offered here are my own. In addition, I would like to thank the following individuals for their help in developing this website: Orion Ackroyd for the photographs of Crotoclypeus sp. and Andrew Smith (Natural History Museum, London) for identifying the specimen. Charles Copp who undertook much of the detailed analysis of the unconformity and provided the basis for Figure 17. Jon Todd (Natural History Museum, London) for helpful comments regarding the fossil bivalves. Andrew Whiteley for the photographs of fossils and hand specimens. Maggie and Peter Williams (University of Liverpool and ESTA) for the annotated ‘field sketches’ generated using PictureToExe software.