The Te Rere and Okareka eruptive episodes — Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand

Abstract

The Te Rere and Okareka eruptive episodes occurred within the Okataina Volcanic Centre at c. 21 000 and 18 000 yr B.P., respectively. The widespread rhyolitic pumice fall deposits of Te Rere Ash (volume 5 km 3 ) and Okareka Ash (6 km 3 ) are only rarely exposed in near-source areas, and locations of their vent areas have been uncertain. New exposures and petrographic and chemical analyses show that the Te Rere episode eruptions occurred from multiple vents, up to 20 km apart, on the Haroharo linear vent zone. The Okareka episode eruptions occurred from vents since buried beneath the Tarawera volcanic massif. Eruption of the rhyolitic Okareka pumice fall was immediately preceded by a small basaltic scoria eruption, apparently from vents close to those for the following rhyolite eruptions. Dacitic mixed pumices scattered within the rhyolite pumice layers immediately overlying the scoria were formed by mixing of the basalt and rhyolite magmas. The Te Rere and Okareka pyroclastic eruptions were both followed by extrusion of voluminous rhyolite lavas. These eruptive episodes mark the commencement of growth of the present-day Haroharo and Tarawera volcanic complexes.

Volcanic stratigraphy and phase chemistry of the 11 900 yr BP Waiohau eruptive episode, Tarawera Volcanic Complex, New Zealand

“…Each of the other rhyolitic eruptions (Okareka, Rerewhakaaitu, and Kaharoa) contain this phase. The occurrence of basaltic ejecta and mingled pumice in the Okareka and Kaharoa events (Nairn 1992;Nairn et al 2001) provides evidence for eruption triggering caused by intrusion of basaltic magma into a silicic magma chamber. The 1886 eruption was entirely basaltic.…”

Interpretation of gravity and magnetic anomalies at Lake Rotomahana: Geological and hydrothermal implications

“…There is evidence of basalt erupted during each of these rhyolite episodes (Nairn, 1992(Nairn, , 2002Darragh et al, 2006;Shane et al, 2007) and it is believed that injections of basaltic magma played a key role in triggering the rhyolitic eruptions (Villamor et al, 2007;Leonard et al, 2002). Basalts predating the 1886 eruption (Nairn, 1979;Nairn and Cole, 1981) have been mapped along the South and North shore of Lake Rotomahana (Fig.2).…”

The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response

“…Of this volume, it is estimated that roughly two-thirds has been eroded and transported into the lake basin (Wilson 2001). The majority of this erosion was accomplished before 22.5 ka, based on localised preservation of the Okareka Tephra (Nairn 1992;Newnham et al 2003) in the loess cover draping the erosion surface. This erosion therefore occurred under the climatic conditions approaching or during the LGM, when the central North Island was colder, windier, and drier than today (Stewart & Neall 1984;Newnham et al 1989).…”