Longitude: -53, Latitude: 71.03
A group of "completely unaltered minor lamprophyre-carbonatite intrusions" in the Umanak area are referred to by Larsen and Moller (1968a, p. 686 and 1968b, p. 83). No other details are given.
K-Ar on biotite gave 600±15 Ma (Larsen and Moller, 1968b).
LARSEN, O. and MOLLER, J. 1968a. Potassium-argon age studies in West Greenland. Canadian Journal of Earth Sciences, 5: 683-91. LARSEN, O. and MOLLER, J. 1968b. K/Ar age determinations from western Greenland. I. Reconnaissance programme. Rapport, Gronlands Geologiske Undersogelse, 15: 82-6