Chronology and dynamics of a large silicic magmatic system: Central Taupo Volcanic Zone, New Zealand

Abstract

The central Taupo Volcanic Zone in New Zealand is a region of intense Quaternary silicic volcanism accompanying rapid extension of continental crust. At least 34 caldera-forming ignimbrite eruptions have produced a complex sequence of relatively short-lived, nested, and/or overlapping volcanic centers over 1.6 m.y. Silicic volcanism at Taupo is similar to the Yellowstone system in size, longevity, thermal flux, and magma output rate. However, Taupo contrasts with Yellowstone in the exceptionally high frequency, but small size, of caldera-forming eruptions. This contrast reflects the thin, rifted nature of the crust, which precludes the development of long-term magmatic cycles at Taupo.

Kawerau Ignimbrite: A 0.24 Ma ignimbrite erupted from the Okataina caldera complex, Taupo Volcanic Zone, New Zealand

“…Distribution, ML, lithic types, and chemistry are inconsistent with a Kapenga, Rotorua, or Reporoa caldera source, and with correlation with ignimbrites of similar mineralogy, chemistry, age, and stratigraphic position. Three other ignimbrites of similar age and stratigraphic position to the Kawerau Ignimbrite have similar field characteristics, but the distinctive hornblende-rich mineralogy, dissimilar chemistry, ML, and lithic-type distribution of the Kawerau Ignimbrite, all suggest it is distinct from other sandy black ignimbrites (Table 1), and it represents a newly recognised ignimbrite within period Illb of Houghton et al (1995).…”

The nature and age of Ohakuri Formation and Ohakuri Group rocks in surface exposures and geothermal drillhole sequences in the central Taupo Volcanic Zone, New Zealand

“…The group includes tuffs, welded ignimbrites, dacite/andesite lavas, and some greywacke pebble conglomerate units that are elsewhere separately named Waikora Formation. However, revisions to the stratigraphy and subsequent age dating (Grindley et al 1994;Houghton et al 1995;Leonard 2003;Gravley 2004;Gravley et al 2006) of surface rocks correlated with the Ohakuri type locality has shown that it is wholly younger than the Whakamaru group ignimbrites. There is thus a dichotomy in use of the term Ohakuri: the type locality and its mapped surface deposits represent a wholly different suite of deposits from those labelled as Ohakuri Group in records from geothermal drillholes.…”

“…However, Healy et al adopted Grindley's (1959) original name "Ohakuri Formation". Based on subsequent 40Ar/39Ar dating (see Houghton et al 1995) for the Whakamaru and Paeroa Ignimbrites, and collective informal grouping of these and other ignimbrites as the Whakamaru group ignimbrites (Wilson et al 1986), the surface to subsurface correlations of Healy et al (1964) and Grindley (1965) implied an age for the Ohakuri of >320-340 ka. In contrast, Martin (1961) …”

Stratigraphy and chronology of a 15 ka sequence of multi‐sourced silicic tephras in a montane peat bog, eastern North Island, New Zealand

“…In addition to providing a tephrochronological framework, our study extends the known geographic distribution of tephras in eastern North Island, which is important for modelling the magnitude and style of tephra-generating eruptions, and for broader volcanic systems' interpretations (e.g., Wilson 1993;Houghton et al 1995;Nairn et al 199? :;Lowe & Newnham 1999;Shane in press).…”