The role that continental margin sediments play in the global carbon cycle and the mitigation of climate change is currently not well understood. Recent research has indicated that these sediments might store large amounts of organic carbon; however, Blue Carbon research continues to focus on vegetated coastal ecosystems as actionable Blue Carbon. Marine sediments are considered emerging Blue Carbon ecosystems, but to decide whether they are actionable requires better quantifications of organic carbon stocks, accumulation rates, and the mitigation potential from avoided emissions. To close some of these knowledge gaps, we spatially predicted organic carbon content, dry bulk density and sediment accumulation rates across the Norwegian margin. The resulting predictions were used to estimate organic carbon stocks in surface sediments and their accumulation rates. We found that organic carbon stocks are two orders of magnitude higher than those of vegetated coastal ecosystems and comparable to terrestrial ecosystems in Norway. Accumulation rates of organic carbon are spatially highly variable and linked to geomorphology and associated sedimentary processes. We identify shelf valleys with a glacial origin as hotspots of organic carbon accumulation with a potentially global role due to their widespread occurrence on formerly glaciated continental margins. The complex and heterogenous nature of continental margins regarding organic carbon accumulation means that to close existing knowledge gaps requires detailed spatial predictions that account for those complexities. Only in this way will it be possible to evaluate whether margin sediments might be actionable Blue Carbon ecosystems.