Oxygenation history of bottom waters in the Cariaco Basin, Venezuela, over the past 578,000 years: Results from redox-sensitive metals (Mo, V, Mn, and Fe)

We present results from analyses of the redox-sensitive metals Mo, V, Mn, and Fe in sediment recovered from the Cariaco Basin (Ocean Drilling Program Leg 165, site 1002). Results are interpreted in the context. of previous studies of delta N-15, export production (percent total organic carbon), eolian input, and hemipelagic deposition in the basin. Variations in redox metal ratios over the past similar to 578,000 years were compared to variations in delta O-18 at Milankovitch frequencies and show a strong relationship between glacial-interglacial cycles in sealevel, governed by the shallow sills encircling Cariaco Basin, and bottom water oxygen content. During 100 kyr and 41 kyr cyclicity, enrichments of Mo and V occur during highly productive interglacials, indicating bottom water anoxia. During glacials, sediments are less depleted or enriched in Mn and Fe relative to the interglacials, reflecting oxic conditions. During 23 kyr and 19 kyr cyclicity, however, these redox metal patterns are not observed, indicating that the Cariaco Basin responds differently to the higher-frequency climate changes.