The Kap Washington Group of post-Palaeozoic explosive volcanic rocks was discovered in 1969 on the north coast of Greenland. Although there have been uncertainties regarding their age and chemical character, they have featured prominently in geotectonic reconstructions of the Arctic regions-in recent interpretations as products of the Yermak hot spot, generated on the Nansen spreading axis during the opening of the Eurasia Basin. We present here new evidence which confirms the volcanicity as end-Cretaceous in age and of peralkaline type. We show that a direct connection with the Yermak hot spot is improbable and infer that the volcanic rocks were generated in a continental extensional rift environment before the break-up of the Laurasian plate in the Arctic. Their age helps to constrain the timing of this poorly understood event.