Age of the volcanoes and granite basement of the Auckland Islands, Southwest Pacific

Abstract

Abstract Potassium-argon age determinations are presented for volcanic rocks and granites of the Auckland Islands, Southwest Pacific Ocean. Two biotite age determinations of granites (94, 96 Ma) confirm the data of previous workers and indicate a pre-Late Cretaceous age for granites at Musgrave Peninsula, Carnley Harbour, and granite boulders in ?Cretaceous conglomerates at Camp Cove, Carnley Harbour. Total-rock age determinations of volcanics of the southern (Carnley) volcanic centre indicate that the Older Basic Series is probably 24–26 Ma old (Late Oligocene), but possibly older (Late Eocene). Volcanism associated with the Newer Basic Series at this centre probably begain about 19 Ma ago (Early Miocene), but the youngest volcanic flows remain undated. In the northern (Ross) volcanic centre, the oldest dated lava flow, at Bivouac Hill, is 19 Ma old (Early Miocene), but a considerable thickness of flows lies beneath this and accordingly may be slightly older. The main sequence of flows around Laurie Harb...