This volume presents an updated version of the final report of the Silurian-Devonian Boundary Committee of the IUGS Commission on Stratigraphy as submitted in 1972. In addition, it contains descriptions of additional areas and discussions of fossil succesions which played an important role in the discussions during the Committee's twelve years of activity. This means that the intention of the book is not simply to trace the boundary wherever it occurs in the world, and that the sections or areas described under a particular geographical heading do not always represent all of the pertinent geology in the region but just the ones that were considered in the discussion or led to a submission.

The authors have been requested to describe not only conditions relating to the boundary level that the Committee ultimately agreed on, but also the one that perhaps most of the involved specialists departed from (Errol I. White's boundary of 1950 at the base of the Ludlow Bone Bed) and any other level that was of importance during the discussions. This has resulted in a reasonably homogenous book with a very good coverage of the problems. Although there was a striking consensus within the Committee on the recommended boundary level, the reader of this volume will easily find very varying opinions on subdivisions and correlations within the sequences below and above the boundary.

The volume bears the insignia of the International Geological Correlation Programme (IGCP), symbolizing the fact that practically every contributor is now involved in Project Ecostratigraphy which was designed to profit from the existence and experience of a well coordinated international group, the momentum generated within it, and the wealth of material and intimate knowledge of the sequence traversed by the new and old boundaries that had been amassed by the members of the Committee. The group has turned from a boundary project to a sequence project, aiming at the "development of biochron correlation at the ecosystem level, using the Wenlockian-Gedinnian as a test sequence". The book is a state of the art report at the beginning of the new project and is expected to be one of the main source books for the proliferating ecostratigraphical working groups.