Alexandra Volcanic Group

Alexandra Volcanic Group (including Okete volcanic field)
Map
Map of selected volcanic features of the Alexandra Volcanic Group and Okete volcanic field. Clicking on the map enlarges it, and enables mouseover of volcano feature/wikilink and ages if available in brackets. The type of basaltic volcanic eruption (some are composite over their eruptive history) is indicated by red being arc basalts, pink being ring basalts of stratovolcanoes and brown being intra-arc basalts typical of those produced by monogenetic volcanic fields. Approximate location of characterised vents are black rectangles with red centres.[1][2][3][4] For wider context see map at North Island Surface Volcanism.
Highest point
Coordinates37°59′35″S 174°59′0″E / 37.99306°S 174.98333°E / -37.99306; 174.98333[1]
Geography
Volcanic field map
Volcanic field map
Alexandra Volcanic Group (including Okete volcanic field)
Geology
Rock ageMiocene to Pliocene(2.74–0.9 Ma)[5]
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Mountain typeVolcanic field
Rock typeBasalt
Last eruption0.9 Ma[1]

The Alexandra Volcanic Group (also known as Alexandra volcanic lineament or Alexandra Volcanics) is a chain of extinct calc-alkalic basaltic stratovolcanoes that were most active between 2.74 and 1.60 million years ago but is now known to have had more recent activity between 1.6 and 0.9 million years ago.[1] They extend inland from Mount Karioi near Raglan with Mount Pirongia being the largest,[2] with Pukehoua on the eastern slopes of Pirongia, Kakepuku, Te Kawa, and Tokanui completing the definitive lineament. The associated, but usually separated geologically basaltic monogenetic Okete volcanic field (also known as the Okete Volcanic Formation or Okete Volcanics), lies mainly between Karioi and Pirongia but extends to the east and is quite scattered.

  1. ^ a b c d Pittari, Adrian; Prentice, Marlena L.; McLeod, Oliver E.; Zadeh, Elham Yousef; Kamp, Peter J. J.; Danišík, Martin; Vincent, Kirsty A. (2021). "Inception of the modern North Island (New Zealand) volcanic setting: spatio-temporal patterns of volcanism between 3.0 and 0.9 Ma" (PDF). New Zealand Journal of Geology and Geophysics. 64 (2–3): 250–272. doi:10.1080/00288306.2021.1915343. S2CID 235736318.
  2. ^ a b McLeod, OE; Pittari, A; Brenna, M; Briggs, RM (2020). Geology of the Pirongia Volcano, Waikato:1:30,000 Geological Map in The Pirongia Volcano. Geoscience Society of New Zealand Wellington, New Zealand. ISBN 978-0-473-52832-4.
  3. ^ Cite error: The named reference Briggs1983 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Briggs1989 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Bischoff2021 was invoked but never defined (see the help page).