Is pore water oxygen content decoupled from productivity on the California Margin? Trace element results from Ocean Drilling Program Hole 1017E, San Lucia slope, California

摘要

+AFs-1+AF0- Trace element evidence from the California Margin (Ocean Drilling Program Hole 1017E) shows significant changes in sediment redox chemistry at intermediate water depths over the last 60 kyr. The influence of export production on intermediate water oxygen content can be distinguished from lateral ventilation through comparisons among proxies representing export production flux ( percent C-org) and sediment-surface (I/Br) and pore water (Mo, Ag, Cd, Re, and U) oxygenation proxies. Sulfate reduction within the uppermost sediment column occurred during late Quaternary interstadials and the Holocene, indicating reduced intermediate water ventilation. However, sulfate reduction was most intense during major interstadials when productivity was enhanced. Decoupling between export production and pore water oxygen content is demonstrated during deglaciation when the sediment pore water oxygen content increases without a corresponding reduction in export productivity. Thus both export production and intermediate water ventilation play a role in oxygen minimum zone processes on the California Margin.