Some Aspects of Western Taranaki Geology and Pedology

Abstract

The North Island of New Zealand is the southern end of an island arc structure which stretches 3000 km northwards to Samoa. It comprises the Hikurangi Trench to the east of the North Island (Houtz, et.al. 1967), a central negative gravity anomaly (Robertson and Reilly 1958) and two volcanic zones to the west of the gravity anomaly (Cole 1967). The volcanic zones comprise the Ohakune-White Island zone of calc-alkaline volcanoes and a western zone of more alkaline volcanoes from Northland to Taranaki. The Taranaki volcanoes are principally high potash low magnesia hornblende-andesites (Hatherton 1968a) which extend 25 km south from New Plymouth to Mt. Egmont. Volcanological investigations on the Taranaki andesites have previously been limited to petrological, geomorphic and Recent tree-ring dating studies. The following work involves detailed studies on the tephrochronology, lahar stratigraphy, weathering and soil formation in western Taranaki together with a detailed interpretation of Quaternary volcanic and climatic events.