Tephras and New Zealand archaeology

Establishing an accurate date for earliest Polynesian settlement in New Zea land is essential for understanding patterns of settlement and associated e nvironmental impacts, and the processes and rates of cultural change in Eas tern Polynesia. Tephra deposits from five volcanic centres, together with e xotic sea-rafted pumice, provide isochronous constraints on the timing of e arliest settlement and human impacts in northern New Zealand. A local basal tic tephra from Rangitoto Island (Auckland) and locally distributed andesit ic tephras from Egmont volcano directly date human occupation to c.AD1400-1 450. Distal andesitic tephras (Tufa Trig Formation) from Mt Ruapehu, Tongar iro volcanic centre, help constrain the timing of earliest anthropogenic de forestation signals in Hawke's Bay. Sea-rafted Loisels Pumice(s), although of uncertain stratigraphic reliability in places, overlies cultural remains that can be no younger than c.AD1350 along the east coast, North Island. T he regionally extensive rhyolitic Kaharoa Tephra, which erupted from Okatai na volcano between c.AD1300-1390, is the critical "settlement layer" datum for dating prehistory in the North Island: no human artefacts are recorded beneath it and the earliest inferred environmental impacts by humans are da ted to c.AD1280, just prior to its deposition. This maximum date matches th e earliest radiocarbon dates derived for both settlement and human impacts from archaeological and natural sites (c.AD1250), and implies that the onse t of deforestation was essentially contemporaneous with initial settlement. The widespread rhyolitic Taupo Tephra, which erupted from Taupo volcano c.A D200, provides an isochronous benchmark well before earliest settlement. Th e tephra may coincide approximately with a putative earlier transient conta ct in New Zealand based on Pacific rat-bone (Rattus exulans) dates. More pr ecise calendrical dates on the tephras-via dendrochronology or ice-core rec ords or other dating methods-would help refine assessment of the timing of earliest settlement, while extending the distributional range of critical t ephra layers, through application of crypto-tephra analysis, could lead to a greater understanding of settlement patterns. Copyright 2000 Academic Pre ss