Kaikoura Orogeny in Northland, New Zealand

Abstract

The Kaikoura system of orogenesis, sedimentation, and volcanism reached a tectonic climax in Northland in the uppermost Oligocene with east-to-west gravity-slide emplacement of an internally disrupted plate of Upper Jurassic oceanic igneous rocks (Tangihua Volcanics) and Cretaceous-Oligocene sedimentary formations. Synorogenic and postorogenic epicontinental marine sedimentation (Waitemata, Otaua, and Parengarenga Groups) extended throughout the Waitakian, Otaian, and Altonian stages of the Lower Miocene. The sediments include distinctive facies derived by marginal collapse of the gravity-slide sheet (Onerahi Chaos-breccia) and by deep erosion of the Tangihua Volcanics (Albany Conglomerate); concurrent volcanic activity (Manukau Breccia, Wairakau Andesites, and Parahaki Volcanics) contributed calc-alkaline debris to the sedimentary basin. Volcanism and marine sedimentation terminated during a post-Altonian episode of profound block-faulting which marked the end of Kaikoura Orogeny in Northland and was followed by a sequence of Upper Tertiary Quaternary subaerial volcanic eruptions. The Mid-Tertiary tectonic timetable for northern New Zealand is similar to that of New Caledonia, New Hebrides, and New Guinea, and seems similarly to have been controlled by a sequence of subduction zones at the interface between the Indian and Pacific plates, and substantial dextral movement on a transform Alpine Fault system.