The Ngatutura Volcanics, Southwest Auckland

Abstract

Basaltic volcanism occurred in three centres at Ohuka, southwest Auckland, in response to late Pliocene-early Pleistocene fault movements. Eruption took place at, or close to, sea level, and volcanoclastic deposits at each centre include agglomerates, sub-aqueous breccias of terrestrial origin, and laharic breccias. Associated flow and dyke rocks are well-jointed, fine-grained alkali olivine basalts which display little variation in their petrographic, mineralogical, and che:nical characters.