The Role of Restricted Basins in Global Biogeochemical Cycles

The formation of restricted basins isolates seawater from the global ocean and allows the formation of salt deposits, often because restricted basins can have minor connectivity to the global ocean and thus can fill and evaporate many times over. The formation of salts removes ions from the global ocean, potentially decreasing their concentration elsewhere and leading to an alteration of their biogeochemical cycle.  The subsequent exposure and chemical weathering of these salt deposits changes the source of these elements back into the global ocean and can influence their biogeochemical cycles for a long time after the formation of the restricted basin.   Sediment biogeochemistry in restricted basins also differs from most global continental shelf, slope, and deep-sea sediments. The formation of sedimentary minerals and their subsequent diagenesis means that the amount and isotopic composition of deposited minerals in restricted basins can differ greatly from those in the global ocean. In this talk I am going to explore how the formation of restricted basins, including epicontinental seas and isolated seas, has influenced the biogeochemical cycle of carbon and sulfur over the course of the last 65 million years.  I am going to use a combination of new measurements on the carbon and sulfur isotopic composition of the ocean over this time to explore how different types of restricted basins influence global biogeochemical cycles in the rest of the ocean. I will argue that the formation of restricted basins has been important in driving changes in the carbon and sulfur isotopic composition of the ocean over time, linking changes in ocean chemistry to tectonics.