High resolution examinations of the solid phase have been performed on a gravity core that shows the typical Amazon fan stratigraphy of the last 20,000 years. The sedimentary record is characterized by two pronounced enrichments of solid phase Fe. The first Fe peak, from 0.34 to 0.37 m sediment depth, consists of an indurated Fe oxyhydroxide crust, located close to the Pleistocene/Holocene boundary. This peak represents a widespread, nonsteady-state, diagenetic feature on the fan. The second Fe peak is a pronounced enrichment of authigenic Fe sulfides, located between 6.15 and 6.45 m in the sediment. The formation of this maximum is attributed to sulfate reduction that is mainly driven by anaerobic methane oxidation. Based on SO42- pore water profiles and calculations of the time of formation of the Fe sulfide enrichment, we conclude that both Fe-rich layers formed more or less simultaneously. The condition that caused both Fe enrichments is a period of nonsteady-state diagenesis, induced by a pronounced decrease in sedimentation and organic carbon accumulation rates between the Pleistocene and the Holocene. During this depositional change, the redox boundaries and reaction fronts were fixed at particular sediment levels for a prolonged time, thus producing higher concentrations of the authigenic minerals than possible under steady-state diagenetic conditions.