I would like to acknowledge at the outset the verysubstantial contributions made by many authors to the establishment of thestratigraphic framework presented in this study. Available space dictatesthat I have only been able to make reference to some of these in the text. Iam particularly grateful to a number of BAS and UK colleagues for theircollaboration in both the field and laboratory over a number of years: G WFarquharson, J E Francis, J R Ineson, D Pirrie, J B Riding and M R AThomson all contributed greatly to the results presented in the paper. Iwould also like to thank A G Beu, A Clarke, E M Harper and J D Taylor,for their very real help over a similar period of time in developing some ofthe theoretical ideas presented here. Financial support from the UK NaturalEnvironment Research Council is gratefully acknowledged, and inparticular: NE/I005803/1. Two referees and the editors are thanked forcomments that helped to improve the manuscript. （）