Waitākere volcano

The Waitākere volcano, also known as the Manukau volcano,[1] was a Miocene era volcano that formed off the west coast of the modern Auckland Region of New Zealand's North Island. Erupting intermittently between 23 million and 15 million years ago, the volcano was at one point one of the tallest mountains in New Zealand. The volcano alternated between periods as a seamount and as a volcanic island, before tectonic forces raised the volcano up from the seafloor 17 million years ago. Volcanism at the site ceased 15 million years ago and the cone has mostly eroded, however the modern Waitākere Ranges are formed from the remnants of the volcano's eastern slopes. A number of visible volcanic sites associated with the Waitākere volcano remain around Auckland, including Pukematekeo, Karekare and Lion Rock.

Waitākere volcano (also Waitakere volcano, Manukau volcano)
Stratigraphic range: Miocene, ~
TypeIgneous
Unit ofNorthland Volcanic Arc
OverliesMurihiku Terrane Greywacke
Lithology
PrimaryAndesite conglomerate and breccia
Location
Coordinates36.9°S 174.3°E / -36.9; 174.3
RegionAuckland
CountryNew Zealand
Type section
Named forWaitākere Ranges

Geological history

The Waitākere volcano began erupting 23 million years ago, beginning life as a seamount adjacent to a deep sedimentary basin. Periodically, the volcano would breach the surface, and be capped by a series of volcanic islands. At its peak, the volcano rose from between 3,000 and 4,000 metres above the sea floor.[2] The volcano had two cones: the major central vent and a smaller cone to the northwest.[3]

The volcano is part of Northland-Mohakatino Volcanic Belt which to the south is still potentially active at Taranaki.[4] This belt forms the western part of a two part extended volcanic arc, which included vents located at the Whangārei Heads, the Hen and Chicken Islands, Whangaroa Harbour, Waipoua Forest and the Kaipara volcano.[5][6][7]

17 million years ago, tectonic forces in the Auckland Region changed, and the Waitākere volcano was uplifted from the seafloor.[2] Vulcanism at the site ceased two million years afterwards.[2] The final two vents were along the Scenic Drive ridge and the modern west coast. Lava from these above sea eruptions form the Lone Kauri Formation of rock.[8]

Most of the volcanic cone eroded five million years ago, except for its uplifted eastern slopes, which form the modern Waitākere Ranges.[2][8] Many remaining volcanic features, such as Lion Rock, are formed from conglomerate rock that is harder and less able to be eroded.[8]

While fossils are rarely found in the Waitākere volcano rocks, some Miocene fossils exist in the Nihotupu Formation of the Manukau Subgroup.[9] These specimens represent deep sea species which lived on the underwater slopes of the volcano.[10][11]

References
  1. Hadden, Peter (2014). North New Zealand: a natural history of the upper North Island. Wairau Press. p. 74. ISBN 9781927158272.
  2. Hayward, Bruce (2009). "Land, Sea and Sky". In Macdonald, Finlay; Kerr, Ruth (eds.). West: The History of Waitakere. Random House. pp. 8–10, 13. ISBN 9781869790080.
  3. Herzer, Richard H. (1 January 1995). "Seismic stratigraphy of a buried volcanic arc, Northland, New Zealand and implications for Neogene subduction". Marine and Petroleum Geology. 12 (5): 511–531. doi:10.1016/0264-8172(95)91506-K. ISSN 0264-8172. Retrieved 30 June 2022.
  4. Bischoff, Alan; Barriera, Andrea; Begg, Mac; Nicola, Andrew; Colea, Jim; Sahoo, Tusar (2020). "Magmatic and Tectonic Interactions Revealed by Buried Volcanoes in Te Riu-a-Māui/Zealandia Sedimentary Basins". New Zealand Journal of Geology and Geophysics. 63: 378–401. doi:10.1080/00288306.2020.1773510. S2CID 221380777.
  5. Hayward, Bruce W. (2017). Out of the Ocean, Into the Fire: History in the Rocks, Fossils and Landforms of Auckland, Northland and Coromandel (PDF). Geoscience Society of New Zealand. title page. ISBN 9780473395964. Retrieved 20 February 2022.
  6. Hayward, Bruce W.; Black, Philippa M.; Smith, Ian E. M.; Ballance, Peter F.; Itaya, Tetsumaru; Doi, Masako; Takagi, Miki; Bergman, Steve; Adams, Chris J.; Herzer, Richard H.; Robertson, David J. (2001). "K-Ar ages of early Miocene arc-type volcanoes in northern New Zealand". New Zealand Journal of Geology and Geophysics. 44 (2): 285–311. doi:10.1080/00288306.2001.9514939. S2CID 128957126. Archived from the original on 25 May 2010. Retrieved 20 April 2010.
  7. Hayward, Bruce W (1979). "Eruptive history of the early to mid Miocene Waitakere volcanic arc, and palaeogeography of the Waitemata Basin, northern New Zealand". Journal of the Royal Society of New Zealand. 9 (3): 297–320. doi:10.1080/03036758.1979.10419410. ISSN 0303-6758.
  8. Hayward, Bruce W. (2006). "The Structure of the Land". In Harvey, Bruce; Harvey, Trixie (eds.). Waitakere Ranges: Ranges of Inspiration, Nature, History, Culture. Waitakere Ranges Protection Society. p. 38. ISBN 978-0-476-00520-4.
  9. Hayward, Bruce W; Triggs, Christopher M (2016). "Using multi-foraminiferal-proxies to resolve the paleogeographic history of a lower Miocene, subduction-related, sedimentary basin (Waitemata Basin, New Zealand)". The Journal of Foraminiferal Research. 46 (3): 285–313. doi:10.2113/gsjfr.46.3.285. ISSN 0096-1191.
  10. Hayward, Bruce W. (2006). "Fossils: Relics of the Past". In Harvey, Bruce; Harvey, Trixie (eds.). Waitakere Ranges: Ranges of Inspiration, Nature, History, Culture. Waitakere Ranges Protection Society. p. 41. ISBN 978-0-476-00520-4.
  11. Eagle, Michael K (1999). "A new Early Miocene Pseudarchaster (Asteroidea: Echinodermata) from New Zealand". New Zealand Journal of Geology and Geophysics. 42 (4): 551–556. doi:10.1080/00288306.1999.9514861. ISSN 0028-8306.
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