Oxygen minimum zone controlled Mn redistribution in Arabian Sea sediments during the late Quaternary

Abstract

Accumulation of labile Mn is related to bottom water oxygen concentrations. In this study we investigate the relation between oxygen minimum zone (OMZ) intensity and Mn burial in Arabian Sea during the late Quaternary. Mn carbonates in sediments of the deep Arabian Basin indicate that this part of the basin remained oxygenated for at least the last 185 kyr. Sequential leaching showed manganese carbonate enrichments with concentrations up to 3750 ppm in deep basin sediments. These Mn spikes must have formed diagenetically during periods of increased Mn oxide fluxes to the deep basin, associated with vertical extension of the OMZ. This extension caused remobilization of Mn oxides from a previously oxic slope, resulting in increased Mn accumulation in the deep basin. Mn relocation is evidenced by synchronous Mn depletions in organic-rich intervals in slope sediments. Mn records from the deep basin can thus be used as a qualitative proxy to reconstruct intermediate water oxygenation.