Rangatauanui

Rangatauanui is a maar lake south of Ohakune in the North Island of New Zealand. It is in the area of the southernmost volcanic activity in the Taupō Rift. Its undisturbed lake sediments have proved useful in reconstructing recent climate proxy records for New Zealand. Geography It is 3 km (1.9 mi) south of Ohakune in the Ngā Roto-o-Rangataua Scenic Reserve, which before 2019 was known as the Ohakune Lakes Scenic Reserve. This has an area of about the about 58 ha (140 acres). Historically it has been called Rangataua Crater Lake. Adjacent is another smaller maar lake, Rangatauaiti, in the area that has been called the Rangataua craters in the geological literature. Geology Along with Rangatauaiti it is a maar lake, believed to have been formed about 30,000 years ago. The nearest other volcanoes are to the north, being the Ohakune volcanic complex and it is unclear if the maar lakes are similar potential Ruapehu parasites, representing the southernmost vents of the Taupō Volcanic Zone which is defined as terminating at Mount Ruapehu. The structure of the southern Ruapehu magma system is unknown and evidence exists in the case of the Ohakune volcanic complex for an approximately 16–18 km (9.9–11.2 mi) depth for the originating magma reservoir, fair magma ascent rates and that the magma conduit may be independent of the main feeder system of Mount Ruapehu. Either way these volcanoes may be the present propagating tip of the arc system that extends from the Taupō Rift through the South Kermadec Ridge Seamounts and Kermadec Islands to beyond Tonga. Because the lake has no major inflows or outflows sediment cores have been undisturbed, and provide a useful dated tephra record of nearby eruptions. Climate studies Consistent with Tasmanian and Chilean studies there is a peak in summer temperatures at about 16,000 years ago similar to the later Holocene. Summer temperatures then cooled from 14.5 to 12.9 cal ka BP, before peaking at 11.7 cal ka BP. Forest developed after 11.5 cal ka BP, similar to today's and the climate record here is consistent with other New Zealand Holocene studies. Ecology Currently the lake is surrounded by wetland for 50 m (160 ft) dominated by New Zealand flax and also containing raupō, mānuka, and cabbage trees. Within the surrounding reserve associated with the two lakes is regenerating native forest containing the trees kahikatea, kāmahi, and rewarewa, as well as the epiphyte northern rātā. Notes References Sources Houghton, B.F.; Hackett, W.R. (1984). "Strombolian and phreatomagmatic deposits of Ohakune Craters, Ruapehu, New Zealand: a complex interaction between external water and rising basaltic magma". Journal of Volcanology and Geothermal Research. 21 (3–4): 207–231. Bibcode:1984JVGR...21..207H. doi:10.1016/0377-0273(84)90023-4. Rees, A.B.; Holt, K.A.; Hinojosa, J.L.; Newnham, R.M.; Eaves, S.; Vandergoes, M.J.; Sessions, A.L.; Wilmshurst, J.M. (2021). "Duelling narratives of chironomids and pollen explain climate enigmas during The Last Glacial-Interglacial transition in North Island New Zealand". Quaternary Science Reviews. 263. 106997. Bibcode:2021QSRv..26306997R. doi:10.1016/j.quascirev.2021.106997. Kósik, S.; Németh, K.; Kereszturi, G.; Procter, J.N.; Zellmer, G.F.; Geshi, N. (2016). "Phreatomagmatic and water-influenced Strombolian eruptions of a small-volume parasitic cone complex on the southern ringplain of Mt. Ruapehu, New Zealand: facies architecture and eruption mechanisms of the Ohakune Volcanic Complex controlled by an unstable fissure eruption". Journal of Volcanology and Geothermal Research. 327: 99–115. Bibcode:2016JVGR..327...99K. doi:10.1016/j.jvolgeores.2016.07.005. Gamble, J. A.; Wright, I. C.; Baker, J. A. (1993). "Seafloor geology and petrology in the oceanic to continental transition zone of the Kermadec-Havre-Taupo Volcanic Zone arc system, New Zealand". New Zealand Journal of Geology and Geophysics. 36 (4): 417–435. Bibcode:1993NZJGG..36..417G. doi:10.1080/00288306.1993.9514588. Archived from the original on 2008-11-22. Booden, M.A.; Smith, I.E.; Mauk, J.L.; Black, P.M. (2010). "Evolving volcanism at the tip of a propagating arc: The earliest high-Mg andesites in northern New Zealand". Journal of Volcanology and Geothermal Research. 195 (2–4): 83–96. Bibcode:2010JVGR..195...83B. doi:10.1016/j.jvolgeores.2010.06.013. Moebis, A. (2010). Understanding the Holocene explosive eruption record of the Tongariro Volcanic Centre, New Zealand: a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand (Doctoral dissertation) (PDF) (Thesis). Massey University.