Black shales have captured the interest of geoscientists since at least the 19th century. A black shale is usually considered to be an organic matter-rich, fine-grained sedimentary rock irrespective of lithology and other petrologic considerations. It was recognised early on that black shale horizons are more than just of local significance, and may in fact be of global importance. With the advent of the Deep Sea Drilling Project and the recovery of black shale horizons from ocean basins – coeval to those previously known from land sections – geoscientists fully recognised the supraregional significance of these horizons. In 1976, time intervals in the Mesozoic characterised by widespread distribution of black shales were termed oceanic anoxic events in recognition of their discrete interbasinal significance, but not implying total global anoxia. Whilst the term was originally intended to include a number of Mesozoic black shale horizons, the term is actually valid for any Phanerozoic time interval associated with perturbations of the global carbon cycle and widespread black shale deposition.
Black shales are unique in a variety of aspects. The requirement of a multidisciplinary approach to their study distinguishes them from the majority of other sedimentary rocks. The contributions to this special issue reflect that multidisciplinarity and represent the current views of black shale deposition and environments. This special issue also represents a holistic approach to black shales, rather than just considering them as the carriers of particular biogeochemical signals. Thus, the sedimentology and stratigraphy of black shale facies associations are at the core of this special issue.