Motutere Tephra Formation and redefinition of Hinemaiaia Tephra formation, Taupo Volcanic Centre, New Zealand

Abstract

Motutere and Hinemaiaia Tephra Formations are moderately widespread rhyolitic tephras erupted from near the southeast margin of Lake Taupo. The 2 multiple-bedded formations constitute a prolonged eruptive sequence interrupted by a short hiatus. The eruptive sequence comprises a plinian-type eruption of coarse pumice lapilli (Motutere Tephra (new name), volume c. 1 kIn 3 ), and further eruptions of a more widespread vitric ash (Hinemaiaia Tephra, volume c. 3 kIn 3 ) apparently related to the growth of a rhyolite dome. Isopach data for both tephras place the eruptive vent near the southeast margin of Lake Taupo in the vicinity of Te Rangiita. Bathymetry and geophysical data suggest the presence of a rhyolite dome 2 kIn offshore and within the vent area.Two unpublished radiocarbon dates of 5370 ± 90 years B.P. (NZ4846A) for Motutere Tephra and 4650 ± 80 years B.P. (NZ4574A) (old T!) for Hinemaiaia Tephra establish the age of these tephras.

Stratigraphy, age, composition, and correlation of late Quaternary tephras interbedded with organic sediments in Waikato lakes, North Island, New Zealand

“…The mineralogical results agree closely with previous findings on pyroclastics and lavas associated with the Taupo, Okataina, and Mayor Island volcanoes (e.g., Ewart 1963Ewart , 1971Cole 1970;Topping & Kohn 1973;Kohn & Glasby 1978;Howorth et al 1980;Buck et al 1981;Froggatt 1981a;Hogg & McCraw 1983;Lowe & Hogg 1986). The results are also consistent with mineralogical analyses of Tongariro and Egmont eruptives, although most published results relate to work done on near-source lavas (e.g., Clark 1960;Gow 1968;Kohn & Neall1973;Cole 1978;Franks 1984;Coleetal.…”

“…To a large extent the dates agree closely with those obtained for the same tephras elsewhere (e.g., Pullar & Heine 1971;Vucetich & Pullar 1973;Cole & Nairn 1975;Froggatt 1981a;Hogg & McCraw 1983), although relatively few dates are available for andesitic eruptives from Tongariro and Egmont (e.g., Topping 1973;.…”

“…Various workers have suggested that a change in slope reflects a change in dispersal mechanism of the tephra, perhaps from turbulent transport near the source to nonnal wind dispersal of finer material further from the source. More recently, however, this flat-lying "fine tail" has been interpreted as representing coignimbrite ashfall rather than Plinian-type fallout material (Sparks & Walker 1977;Froggatt 1982b;Fisher & Schmincke 1984). Secondary thickening of distal tephra deposits has also been attributed to premature fallout because of particle aggregation or scavenging (Cas & Wright 1987 Fig_ 12 Provisional isopach maps for 11 tephras in the Waikato area, based on measurements from lake sediment cores (see Fig.…”

Stratigraphy and chronology of the Stent tephra, a c. 4000 year old distal silicic tephra from Taupo Volcanic Centre, New Zealand

“…Radiocarbon samples obtained immediately above and below the tephra yielded ages of 4060 ± 80 (Wk 1443A) and 3910 ± 110 yr B.P. (Wk-1444A), respectively Whakaipo Tephra (as defined by Vucetich & Pullar 1973) (also directly dated) was identified at c. 2 m depth, together with Hinemaiaia Tephra (as defined by Froggatt 1981c andLowe 1986) at c. 4 m depth. Radiocarbon samples directly above Hinemaiaia Tephra, and 0.25 m below it, constrained its age (Fig.…”

“…However, Wilson (1993) has now constructed anew detailed stratigraphy and identified 28 eruptions postdating the c. 22.6 ka Kawakawa (Oruanui) eruption. Hinemaiaia Tephra, previously defined by Froggatt (1981c), was reinterpreted by Wilson to represent 10 discrete units erupted between 3950 and 5200 yr B.P., these units being separated on the basis of intervening weak paleosols and/or erosion breaks. These newly identified units have been mapped, but correlation of individual units from source was difficult because many rarely exceed 0.20 m thickness and they rapidly merge together.…”