Depth localization of denitrification in a deep-sea sediment from the Madeira Abyssal Plain

Sediments of the Madeira Abyssal Plain are dominated by alternate sequences of pelagic sediment and “turbidites” composed of relatively organic-rich material transported from the continental margin. After the deposition of a turbidite and resumption of pelagic sedimentation, the zones of O2 and NO3− respiration progress slowly into the turbidite from above. The oxidation front is characterized by depletion of O2 and NO3 at almost identical depths. Data are presented to show that NO3− respiration (denitrification) within such a turbidite is localized in a very small depth interval at the oxidation front.