RECONSTRUCTING THE IRON CYCLE FROM THE HORIZONTAL DISTRIBUTION OF METALS IN THE SEDIMENT OF BALDEGGERSEE

In Baldeggersee, the distributions of solid phase Fe, Mn, V, Cr, As an d Mo were determined in different sediment strata, deposited under var ious deep-water oxygen conditions. Iron concentrations are correlated with water depth when an anoxic sediment is in contact with an oxic wa ter column. Benthic redox gradients trigger iron transport towards the deepest site (geochemical focusing) and loss of iron from the shallow er parts through the outflow. Fe cycling in the lake is inhibited by o xygen penetration into the sediment. Vanadium and arsenic can be used as tracers for the internal Fe cycle. Their distribution patterns are highly correlated with iron. In case of a stable oxycline in the deep water, Mo is enriched in the sediment and correlates with Mn. The hori zontal distribution patterns of Fe, V, As and the correlation of Fe an d Mn with trace metals are promising proxy indicators for the reconstr uction of deep-water oxygen conditions during deposition.