[en] The Kap Washington Group, Peary Land, North Greenland, is a bedded suite of rhyolitic lavas and tuffs that forms the northernmost rock province of Greenland. The volcanic group borders on the north the Palaeozoic North Greenland fold belt from which it is separated by the sourtherly-dipping Kap Cannon thrust. K/Ar whole-rock age determinations of 34.9+-5.3 m.y. and 32.3+-3.2 m.y. on somewhat mylonitised lava samples were earlier regarded as giving an approximate minimum age volcanic consolidation and a maximum age of the Kap Cannon thrusting. This note reports on Rb/Sr isotopic work that dates the Kap Washington Group, the five samples processed suggesting an age of about 63 m.y. Thus the general age of extrusion and consolidation of the volcanic pile is considered to be earliest Tertiary. (author)