A MULTIPLE-SOURCE HOLOCENE TEPHRA SEQUENCE FROM LAKE TUTIRA, HAWKES BAY, NEW-ZEALAND

A core drilled in a swamp at the northern end of Lake Tutira, northern Hawke's Bay, New Zealand, as part of a programme to determine the ero sion history of the Lake Tutira catchment, contains 14 tephra layers ( 10 rhyolitic and 4 andesitic). The mineralogy of each layer was determ ined, together with electron microprobe chemistry of glass shards, and of hornblendes from two of the andesitic tephras. The rhyolitic layer s are identified from their stratigraphic position, mineralogy, and gl ass/mineral chemistry as: Taupo (1850 conventional radiocarbon years o ld), Mapara (2160 yr), Whakaipo (2685 yr), Waimihia (3280 yr), Hinemai aia (4510 yr), Whakatane (4830 yr), and Motutere (5430 yr), but three additional rhyolitic layers (aged c. 3700, 4100, and 4300 yr) could no t be correlated with known tephras. Two are possibly reworked layers, but one (c. 4300 yr) may represent a new tephra which has not been pre viously recognised. The mineralogy of three of the andesitic tephras ( aged c. 3100, 4900, and 6000 yr) indicates that they were probably der ived from Egmont Volcanic Centre, and tentative correlations are sugge sted for them. The fourth andesitic tephra (c. 5400 yr) is probably de rived from Tongariro Volcanic Centre. Nine radiocarbon ages were obtai ned from the core and two of these, 6530 +/- 110 yr B.P and 6330 +/- 7 0 yr B.P located near the base of the core, indicate that Lake Tutira formed c. 6500 years ago.