Surface sediments interact with underlying sedimentary sequences and geologic reservoirs. Organic matter preserved in surface sediments is microbially degraded in the deep subsurface while the chemical composition of buried sediments and pore fluids is strongly altered by various diagenetic processes. Methane produced by the decomposition of buried organic matter within the deep biosphere is either trapped as sedimentary gas hydrate or returned towards the surface via fluid and gas migration. A significant fraction of methane and other chemicals ascending towards the surface is consumed by microbial and chemical processes in cold seep and mud volcano sediments. Marine surface sediments are thus regulating the flux of particulate matter into the deep subsurface and the return flux of dissolved and gaseous species into the ocean. Methane hydrates are probably the most important product of the deep biosphere. They are only stable under low temperatures and may thus response to global warming. Moreover, they harbor vast amounts of natural gas and may thus be exploited as a new unconventional resource of fossil energy. Quantifying the burial of organic matter, gas hydrates and other solids and the return fluxes of dissolved and gaseous species into the ocean is thus a major challenge and opportunity for research unit Marine Geosystems.
Marine expeditions to offshore gas hydrate deposits and associated cold seeps and mud volcanoes are conducted on a regular basis by research unit Marine Geosystems. During these cruises, various methods are applied to study the ascent of deep-seated fluids and gases, to characterize the geochemical environment of the source region, to investigate the turnover of methane in marine surface sediments and to quantify the emissions of methane into the overlying water column. The research unit also develops and applies basin modeling tools to simulate the formation of gas hydrates in marine sediments.
New approaches for the environmentally sound production of natural gas from marine gas hydrates are developed within the SUGAR project (Submarine Gas Hydrate Reservoirs). This national German program on applied gas hydrate research is led by research unit Marine Geosystems. It aims to use CO2 from coal power plants and industrial sources to release and produce natural gas from methane hydrates and to sequester CO2 as solid CO2 hydrate. Cutting-edge high-pressure laboratories and reservoir modeling tools are developed within the research unit to advance these technologies.