Phanerozoic organic-carbon-rich marine sediments: Overview and future research challenges

“One of the major obsessions of many early workers, to the mid-1900s, was the application of uniformitarian principles to depositional models for black shales“ (Arthur and Sageman, 1994).The purpose of this overview of organic-carbon(OC)-rich marine sediments is to provide a brief but current summary of the historical developments, principle concepts, and remaining challenges in integrated sapropel and black shale research. As such, it provides a substantive introduction to the Special Issue of Palaeogeography, Palaeoclimatology, Palaeoecology on “Organic Carbon Rich Sediments through the Phanerozoic: Processes, Progress, and Perspectives”. Given this focused scope, the overview does not aim to be comprehensive or complete but to provide a solid setting for the fourteen individual research papers that constitute this Special Issue and two previous special issues (Meyers and Negri, 2003; Negri et al., 2006) that cover research aspects complementary to this one. Like the individual contributions, this introduction and overview is organized into Cenozoic, Mesozoic, and Palaeozoic units. The Cenozoic and Palaeozoic units are deliberately larger than theMesozoic unit, acknowledging that much ground on Mesozoic black shale is already covered in the two previous special issues. Because the Late Cenozoic sapropels of the Mediterranean Basin have been extensively studied, understanding how these near-modern analogs of ancient black shales were deposited provides a good foundation for understanding how the older sequences may have evolved. In contrast, because far less is generally known about the black shales of the Palaeozoic than comparable OC-rich sequences of either the Cenozoic or the Mesozoic, a more comprehensive summary and comparison of the more ancient sequences is particularly appropriate to the theme of this Special Issue.