The Genetic Units Project and GEOTIPE projects based at Heriot-Watt University and their respective sponsoring companies are thanked for their financial support. Fieldwork has been supplemented by an AAPG grants-in-aid fieldwork award. David Crawford of Survey Development Services Ltd, Dan Eng of Bentley Microstation, Peter Fenning of Survey Development Systems Ltd., Randy Kolesar of Seismic Image Software Ltd. and Lynsey Anderson of Roxar RMS are acknowledged for their computer software support. Aerial photographs used to create Figures 2 and 6 are courtesy of Institut Géographique National (IGN) Paris, (1995-Mission FD 04 - 1:20 000 nos. 7585-7589, 7687-7693, and 7702-7704) and Cambridge Air Photograph Company respectively. Malcolm Arnot is acknowledged for his thoughts, ideas and constructive comments. The authors also wish to acknowledge Dom Tatum, Matt Porter, and Justyn Clark for field assistance.