A 6500-year-old history of tephra deposition recorded in the sediments of Lake Tutira, eastern North Island, New Zealand

Lake Tutira is a small lake formed as a result of a landslide about 6500 radiocarbon years BP. It is situated 100 km east, and downwind, of the central North Island volcanoes and has provided a trap for tephras which have erupted since the mid-Holocene. Detailed studies of cores from the lake and adjacent swamps have revealed 23 tephra layers, which represent tephra deposition into Lake Tutira every 300 years on average. Sixteen of these layers are macroscopic and seven are microscopic, occurring as concentrations of volcanic glass. The tephra layers mark rhyolitic and andesitic tephra eruptions from Taupo, Okataina, Egmont, and Tongariro volcanic centres. They were identified using their ferromagnesian mineralogy, major element compositions of glass shards, and their stratigraphic position, particularly with respect to radiocarbon dates. The Lake Tutira tephra record is the most detailed record yet found in eastern North Island, and the detection of microscopic tephra layers indicates the value of lake sediments and swamps as traps for distal tephras. Copyright (C) 1996 INQUA/Elsevier Science Ltd