Age Relations of the Dunedin Volcanic Complex and Some Paleogeographic Implications—Part I

Abstract

Marine inliers at Dowling Bay - Waipuna Bay and Blanket Bay on the northern shores of Otago Harbour are of Waiauan, or at youngest, early Tongaporutuan age. They contain mixed basaltic and trachytic tuffs of the Initial Eruptive Phase at a number of horizons among their upper members, thus fixing the date of initiation of volcanic activity. The beds pass conformably upwards into basaltic tuffs followed by flow-rocks of the First Major Eruptive Phase. The sediments comprise massive and laminated micaceous sandstones, calcareous sandstones and fetid limestones (Dowling Bay Limestone) as well as the interbedded water-lain tuffs. All these, up to the top of the highest sandy layer at Waipuna Bay, are grouped as the Waipuna Bay Formation. They are derived mostly from the Otago schists, but contain minor microcline of granitic or high-grade metamorphic parentage. Outward dips of the sediments and overlying volcanics are ascribed to doming by magmatic intrusions. © 1960 Taylor & Francis Group, LLC. All rights reserved.