Contrasting molybdenum cycling and isotopic properties in euxinic versus non-euxinic sediments and sedimentary rocks: Refining the paleoproxies

The redox-sensitive transition element molybdenum is present in the Earth's crust at trace concentrations but is abundant in seawater, marine sediments, and ancient sedimentary rocks. These occurrences have led to the development of a suite of paleoredox proxies based on the bulk concentration of Mo, its isotopic composition, and the covariation of Mo with total organic carbon (TOC) in ancient black shales. However, these proxies have almost...