PREFACE

Study of depositional sequences and development of the concepts and principles of sequence stratigraphy owe their beginnings and formulation to many people. Since 1930, those working with Pennsylvanian strata have examined Weller's (1930) 'cyclothems ' and Moore's (1958) 'megacyclothems ' and argued various origins for them ranging from local tectonism on the one hand to eustatic changes in sea level on the other hand and included numerous other origins based on climatic changes and orogenesis. The idea that systemic boundaries were the result of worldwide orogenies had been discredited and laid to rest only a few years earlier in the late 1920's, so ideas that worldwide sea level might have ha