STRATIGRAPHY AND CHRONOLOGY OF THE STENT TEPHRA, A C-4000 YEAR-OLD DISTAL SILICIC TEPHRA FROM TAUPO-VOLCANIC-CENTER, NEW-ZEALAND

Tephrostratigraphic and chronologic studies in two areas of the North Island have identified a previously unrecorded, thin, distal silicic t ephra derived from the Taupo Volcanic Centre. In Taranaki, three radio carbon ages of the uncorrelated tephra are consistent with the indepen dent radiocarbon chronology obtained from enveloping Egmont-sourced te phras. In western Bay of Plenty, where the uncorrelated tephra is also directly dated, it is overlain by Whakaipo Tephra (c. 2.7 ka) and und erlain by Hinemaiaia Tephra (c. 4.5 ka). From these sites in Taranaki and western Bay of Plenty, seven radiocarbon dates obtained on the unc orrelated silicic tephra yield an error-weighted mean age of 3970 +/- 31 conventional radiocarbon years B.P. The ages on the uncorrelated te phra (informally referred to as Stent tephra) from both areas are stat istically identical but significantly different from those on both Wai mihia and Hinemaiaia Tephras. The occurrence of Stent tephra in Tarana ki, c. 160 km upwind from the postulated source area, and in western B ay of Plenty, suggests that it represents the product of a moderately large plinian eruption. Until recently, its validity as a discrete eru ptive event had been problematical, because a near-source equivalent d eposit between Waimihia and Hinemaiaia Tephras was not recognised in t he Taupo area. However, a revised stratigraphy proposed by C. J. N. Wi lson in 1993 for eastern sectors of the Taupo area shows that multiple tephra layers were erupted from Taupo volcano between c. 3.9 and 5.2 ka. Of these newly recognised layers, unit-Q-the product of a moderate ly large eruption (greater-than-or-equal-to 0.15 km3) at c. 4.0 ka-is tentatively correlated with Stent tephra. Other eruptive units recogni sed by Wilson are either too old or too small in volume to be consider ed as likely correlatives.