The area to the northwest of Svalbard was repeatedly affected by tectono-magmatic events during the opening of the Arctic Ocean including the formation of the Cretaceous High Arctic Large Igneous Province, the Late Cretaceous/early Cenozoic birth of the Eurasian Basin, and the establishment of a full seafloor-spreading regime along the Lena Trough/Fram Strait in the middle Miocene. These processes also affected the Sophia Basin located between the Yermak Plateau and the northern Svalbard Shelf. In 2013 a piece of basalt was dredged from the southern flank of the Mosby Seamount, the central landmark within the Sophia Basin. According to Ar–Ar dating on fresh plagioclase the basalt erupted at ~ 13 Ma, contemporaneous with incipient seafloor spreading in the nearby Lena Trough and volcanic activity on northern Svalbard. If the dredged basalt is temporally related to sediment-covered lava flows and sill intrusions around Mosby Seamount, which were revealed by seismic reflections, then the age of the sedimentary cover must be middle Miocene or younger. This finding will improve the regional seismo-stratigraphy.