Stratigraphy of New Zealand's Cenozoic volcanism north-west of the Volcanic Belt

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Abstract
The several methods for dating vo1canic formations are reviewed. They are: superposition (including the relationship to eustatic terraces), local and distant fossils, radiocarbon, petrology, paleomagnetism, weathering and erosion of rocks, and erosion of cones. The stratigraphic data of the many volcanic formations north-west of the Volcanic Belt are summarized in a figure and a table. The distribution of andesites, dacites, and rhyolites (as opposed to that of basalts) tends to be paral1e1 to the main arcuate structures of the North Island. For any single Hthologic type, the younger volcanic arcs tend to be to the east, and within anyone arc the latest volcanic foci tend to be in the south. The sequence of volcanism is inferred to be: andesite (oldest), dacite, rhyolite, anel basalt (youngest); with tectonic activity extending possibly from as early as late in the andesite volcanicity, through possibly into the period of rhyolite eruptions. The fact that the present-day eruptions at Tongariro National Park are andesitic may be explained by a southward shift of volcanic foci to that area, rather than by an assumption that andesite eruptions are a late phase of volcanism.

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