A detailed geochemical analysis of iron and sulfur speciation in sediments recovered during Leg 207 on the Demerara Rise show that the paleoenvironment was euxinic during Cretaceous black shale deposition with iron sulfides being formed in the sulfidic part of the water column and the sediment. This requires the transport of iron to the place of iron sulfide formation, for instance, via an intense but not sulfidic OMZ. In addition, OM acted as an important early diagenetic sink for dissolved reduced/intermediate sulfur species at (present) OM contents exceeding ~2 wt%. Results from the five different sites demonstrate that environmental redox conditions were not constant with time. A more detailed analysis of iron-sulfur speciation during black shale deposition at Sites 1258 and 1260 together with sulfur isotope partitioning between sulfur species is needed and is currently being carried out to identify the frequency of changes in water column euxinia during black shale deposition with time in relation to the availability of iron.