POSSIBLE RELATIONSHIPS BETWEEN LATE DEVONIAN ALPINE GLACIATION AND BLACK SHALES
This occurrence also points out an important association between glaciation and black shales. Glacial meltwater is a major source of terrestrial nutrients and dissolved organic matter that can stimulate organic productivity in nearby seas, and iceberg-prone seas are typically areas of enhanced organic productivity and sequestration of organic carbon in underlying sediments. In addition, glacial meltwater draining into adjacent seas commonly generates a fresher, lighter, surface layer that initiates a salinity stratification, or halocline, and this kind of density stratification may prevent circulation of oxygen-rich surface water to greater depths, thereby promoting anoxia below the halocline. Hence, Late Devonian tidewater glaciation may have contributed to both anoxia and enhanced organic productivity, and at least for upper parts of the Cleveland Shale, coeval glaciation must now be considered as another control on organic-rich sedimentation.