This book forms the first of a two part volume containing a compilation of 35 classic papers on extensional tectonics, with particular emphasis on petroleum-related features. Each part comprises a set of scientifically significant papers from the last 20 years taken from the Journal of the Geological Society and various Special Publications of the Geological Society. The present volume focuses on regional scale processes under the headings: Mechanical and Thermal Consequences of Extensional Basin Formation; Stratigraphic Consequences of Extensional Tectonics; and The Uplift and Erosion of Sedimentary Basins and the Role of Overpressure. The book begins with a new scientific and historical review of the subject and the context of the papers contained therein.