K-Ar AGES FOR THE TERTIARY OF EAST GREENLAND

• Main Authors: Robert D. Beckinsale, C. Kent, Brooks, David C. Rex
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Greenland; Angmagssalik; East Greenland; North Atlantic; Scoresbysund; Shannon
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.473.5462; http://2dgf.dk/xpdf/bull20-01-27-37.pdf

K-Ar whole-rock ages of extrusive rocks from the Tertiary of East Greenland show variable argon loss but the oldest ages of 55-60 m.y. are similar to those found for basalt plateaux elsewhere in the North Atlantic Tertiary province. The pattern of ages from samples collected serially in a vertical traverse of a single flow is discussed. Minerals separated from intrusive rocks show the effects of slow cooling and different retentivities for radiogenic 40Ar with biotites giving generally younger ages than amphiboles. The later give ages clustering around 50 m.y. which is marginally younger than ages for Tertiary instrusions in the British Isles and West Greenland. The long cooling history recorded in the biotite ages is consistent with evidence for deep burial found in the lowest basalts. Tertiary igneous rocks outcrop over considerable areas in East Greenland between Angmagssalik (lat. 66°) and Scoresbysund (lat. 70°), while more scattered occurrences are found as far north as Shannon 0 (lat. 75°). A