Sulfate reduction is not the most important mechanism affecting metal accumulation in Mejillones Bay, probably due to the presence of Thioploca, which inhibits the pyrite formation and the metal-sulfide reaction. We propose the use of the authigenic Mo/U ratio and a preliminary statistical model to reconstruct the levels of paleoxygenation in the subsurface waters of Mejillones Bay, by analyzing the same metals measured throughout the sedimentary sequences (and using the same statistical procedure), at least to identify extreme variations of the OMZ in this bay of northern Chile. (C) 2014 Elsevier B.V. All rights reserved.