Marine phosphorites, the principal raw material for phosphatic fertilizers, do not occur uniformly through time and space. The origin of these unusual sedimentary rocks appears to be related mainly to marine biological productivity, often associated with upwelling currents during certain intervals of geological time. This book examines the environmental setting and resulting phosphorites which formed during the Miocene, one of the major and most recent phosphogenic periods throughout the geologic record. In addition, an oceanographic perspective is given by investigations of modern oceanic environments where phosphorites are presently forming. Together, the geologic and marine approaches provide a complete outlook on this important mineral resource. This book is the third of four reference volumes which together cover the achievements of the International Geological Correlation Programme Project 156 (Phosphorites) during the ten years of the project’s existence.