A prolific Tertiary source rock of terrestrial origin in the eastern Nordic Seas

This study evaluates the source rock potential, organic matter input, and depositional environments of Miocene-aged sediments in the eastern Nordic Seas. It focuses on ODP/IODP Sites 909, 985, and 1572, two exploration wells (7316/5-1 and 6608/10-1), and oil seeps offshore western Svalbard. Integrated marine palynological, biomarker, and geochemical analyses indicate a mainly Early to Middle Miocene age and a mixed terrestrial-marine origin of the sedimentary organic matter and associated oil seeps. Angiosperm-derived biomarkers, especially triterpenoids like oleananes and oleanenes, are abundant and help link seeping oils to deltaic terrestrial sources. Depositional settings ranged from oxic in the Fram Strait (Hole 909C) to dysoxic or anoxic in southern Sites (Holes 985A and 1572B), influenced by the semi-enclosed Nordic Seas. Geochemical indicators such as sulfur content, TOC/S ratios, and Pr/Ph values reflect variations in bottom water oxygenation and sediment conditions. Terrestrial organic input is linked to Miocene deltaic systems, likely formed by tectonic uplift in East Greenland, the Barents Sea, and central Norway. Basin modeling in the southwestern Barents Sea, using seismic and well data, shows that Miocene source rocks have reached maturity levels sufficient for hydrocarbon generation, especially beneath thick Plio-Pleistocene glacial overburden. The presence of oleanene and oleanane in both boreholes and oil seeps supports the conclusion that these Miocene source rocks are regionally widespread and part of an active petroleum system. • Oil seep and source rock correlation reveal that Miocene sediments in the eastern Nordic Seas contain significant contributions from terrestrial angiosperms. The widespread presence of triterpenoids like oleananes and oleanenes directly links these source rocks to deltaic systems influenced by regional tectonic uplift. • The organic-rich Miocene sediments of the Nordic Seas are conceptually discussed with prolific systems like the Niger Delta and Congo deep-sea fan, highlighting the significance of terrestrial input in generating source rock potential in marginal marine settings. • Basin modeling and biomarker evidence from boreholes and oil seeps confirm that Miocene source rocks are thermally mature and capable of hydrocarbon generation – particularly where thick Plio-Pleistocene overburden exists – indicating a novel, regionally extensive and active petroleum system in the eastern Nordic Seas.