Molybdenum isotope signatures in continental margin marine sediments

We present molybdenum isotope data for four sediment profiles from continental margin settings. Each profile has a distinctive average isotope composition ranging from δ98 / 95Mo − 0.5‰ to 1.3‰ (relative to J and M laboratory standard). This range lies between the modern ocean water value (2.3‰) and the values typical of Mo adsorbed onto Mn oxides (− 0.7‰ ± 0.1‰). An important finding of this study is the apparent co-variation between the Mo isotope composition and the accumulation rate of authigenic Mo under reducing conditions. This relationship suggests that the chemical processes responsible for Mo accumulation under reducing conditions produce an isotope signature in marine sediments. In addition to the relationship between Mo accumulation and the Mo isotope signature there is also a relationship between these parameters and the rate of organic carbon oxidation and burial. These relationships suggest that the Mo isotope signature of reducing sediments may serve as a tracer for the cycling of organic carbon in continental margin sediments; however, additional data will be required to refine any such relationships.