Ohinewai Tephra Formation; ac.150000-year-old tephra marker in New Zealand

Abstract
The stratigraphic rank of Ohinewai Tephra Formation is proposed for Ohinewai Ash Member (basal member of Hamilton Ash Formation) at the type section and newly defined reference sections at Te Kuiti, and Tirau, and at Sapphire Springs, Tauranga, and Opape in Bay of Plenty B.P. An eruptive source near Taupo is indicated. An estimated age is c. 150000 years B.P. The weathered form of Ohinewai Tephra at these reference sections has the general character of Te Uku Variant but with variations depending on the proportion of allophane to halloysite. Ohinewai Tephra is commonly contrasted with older rhyolitic tephras in which the proportion of allophane to halloysite is much lower.

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