Abstract:

The Kap Washington Group volcanic sequence is exposed on the north coast of Greenland. The sequence was erupted in a continental rift setting during the opening of the Arctic Ocean and provides important geological constraints on the timing of this event. In this study we present the first isotope dilution thermal ionization mass spectrometry U–Pb zircon ages from 10 samples of trachytic to rhyolitic composition. Samples from Lockwood Island (n = 4) gave concordant ages between 67.2 ± 0.5 and 61.0 ± 0.3 Ma (2σ). Lavas from Kap Kane (n = 5) yielded concordant ages between 70.5 ± 0.3 and 69.7 ± 0.2 Ma. An ignimbrite from the Kap Washington peninsula yielded a concordant age of 68.5 ± 0.3 Ma. The Kap Washington Group sequence and similar occurrences on Ellesmere Island record a prolonged period of continental rift volcanism lasting from 92 to 58 Ma. We propose that this volcanism occurred along the margins of a nascent Eurasia Basin undergoing east–west extension linked to rifting in the Labrador Sea–Baffin Bay system.

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