Around 1,840 million years ago, a widespread transition to euxinia occurred along productive continental margins.
Anoxic sulﬁdic conditions extended outward from near-shore to the mid-shelf, and were overlain by oxic surface waters and underlain by anoxic and Fe-rich (ferruginous) water maintaining the redox stratiﬁcation of the ocean, which developed with the evolution of oxygenic photosynthesis. Widespread sulfidic conditions throughout the Mesoproterozoic have been implicated in the protracted oxygenation of the atmosphere and slow rates of eukaryotic evolution. However, the continuation of ferruginous deep water conditions through the Mesoproterozoic, with sulfidic conditions limited to areas of high organic carbon production, highlights that the controls on productivity, and oxygenic productivity in particular, remain poorly understood.
Linda Godfrey and colleagues report new nitrogen and carbon isotope data for sediments from six drill cores that provide a 350-km-long oblique transect to the paleo-coastline of the Animikie Basin on the margin of Superior Province, North America.
Linda V. Godfrey et al., DOI: 10.1130/G33930.1.