title: Quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on Chatham Island, east of New Zealand, southwest Pacific Ocean

authors: Holt, Katherine A.

subjects: Kawakawa tephra

abstract: Tephras provide one of the most reliable methods of time control and synchronisation within Quaternary sequences. We report on the identification of two widespread rhyolitic tephras - the Kawakawa and Rangitawa tephras - preserved in extensive peat deposits on Chatham Island  900 km east of New Zealand. The tephras, both products of supereruptions from the Taupo Volcanic Zone, occur as pale, fine-ash dominated layers typically 10-150 mm thick. Mineralogically they are dominated by rhyolitic glass, together with subordinate amounts of quartz, feldspar, hypersthene, hornblende, Fe-Ti oxides and zircon. Phlogopite/biotite was identified additionally in Rangitawa Tephra. Ages for each tephra were obtained via mineralogical and major element glass composition-based correlation with well-dated equivalent deposits on mainland New Zealand, and we also obtained a new zircon fission-track age for Rangitawa Tephra (350 ± 50 ka) on Chatham Island. Both tephras were erupted at critical times for palaeoenvironmental reconstructions in the New Zealand region: the Kawakawa at ca. 27 cal. ka, near the beginning of the  extended  LGM early in marine isotope stage (MIS) 2; and the Rangitawa at ca. 350 ka near the end of MIS 10. The time constraints provided by the tephras demonstrate that Chatham Island peats contain long-distance pollen derived from mainland New Zealand, which provides a reliable proxy for identifying glacial-interglacial climate conditions, in this case during the MIS 11-10 and MIS 2-1 cycles. The two tephras thus provide important chronostratigraphic tie-points that facilitate correlation and synchronisation not only across the Quaternary deposits of the Chatham Islands group but also with climatically significant terrestrial and marine records in the wider New Zealand region.

text: Quaternary tephra marker beds and their potential for palaeoenvironmental reconstruction on Chatham Island, east of New Zealand, southwest Pacific Ocean Tephras provide one of the most reliable methods of time control and synchronisation within Quaternary sequences. We report on the identification of two widespread rhyolitic tephras - the Kawakawa and Rangitawa tephras - preserved in extensive peat deposits on Chatham Island  900 km east of New Zealand. The tephras, both products of supereruptions from the Taupo Volcanic Zone, occur as pale, fine-ash dominated layers typically 10-150 mm thick. Mineralogically they are dominated by rhyolitic glass, together with subordinate amounts of quartz, feldspar, hypersthene, hornblende, Fe-Ti oxides and zircon. Phlogopite/biotite was identified additionally in Rangitawa Tephra. Ages for each tephra were obtained via mineralogical and major element glass composition-based correlation with well-dated equivalent deposits on mainland New Zealand, and we also obtained a new zircon fission-track age for Rangitawa Tephra (350 ± 50 ka) on Chatham Island. Both tephras were erupted at critical times for palaeoenvironmental reconstructions in the New Zealand region: the Kawakawa at ca. 27 cal. ka, near the beginning of the  extended  LGM early in marine isotope stage (MIS) 2; and the Rangitawa at ca. 350 ka near the end of MIS 10. The time constraints provided by the tephras demonstrate that Chatham Island peats contain long-distance pollen derived from mainland New Zealand, which provides a reliable proxy for identifying glacial-interglacial climate conditions, in this case during the MIS 11-10 and MIS 2-1 cycles. The two tephras thus provide important chronostratigraphic tie-points that facilitate correlation and synchronisation not only across the Quaternary deposits of the Chatham Islands group but also with climatically significant terrestrial and marine records in the wider New Zealand region.

year: 2010

title: Linking proximal ignimbrites and coeval distal tephra deposits to establish a record of voluminous Early Quaternary (2.4–1.9 Ma) volcanism of the Tauranga Volcanic Centre, New Zealand

authors: Prentice, Marlena Lee

subjects: Taupō Volcanic Zone

abstract: The Tauranga Volcanic Centre (TgaVC) of the North Island, New Zealand, was active from 2.95 to 1.9 Ma. It lies temporally and spatially between the currently active Taupō Volcanic Zone, one of the most productive regions of Quaternary silicic volcanism globally, and its predecessor, the Coromandel Volcanic Zone. This study provides an enhanced chronology for pyroclastic volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite). These eruptives were followed by the eruption of the large-volume Waiteariki Ignimbrite at 2.1 Ma. In northern Hawke’s Bay (150-170 km southeast of TgaVC), several distal tephra-fall horizons and an ignimbrite (Hikuroa Pumice Member) are preserved in marine-hosted sediments and are stratigraphically equivalent to the five ignimbrites of the TgaVC. Using new major- and trace-element data on glass in conjunction with new zircon-derived U-Pb ages, a correlation between the Hawke’s Bay tephras and the TgaVC ignimbrites is established and the Hikuroa Pumice Member is confirmed as the distal deposit of the Waiteariki Ignimbrite. The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs.

text: Linking proximal ignimbrites and coeval distal tephra deposits to establish a record of voluminous Early Quaternary (2.4–1.9 Ma) volcanism of the Tauranga Volcanic Centre, New Zealand The Tauranga Volcanic Centre (TgaVC) of the North Island, New Zealand, was active from 2.95 to 1.9 Ma. It lies temporally and spatially between the currently active Taupō Volcanic Zone, one of the most productive regions of Quaternary silicic volcanism globally, and its predecessor, the Coromandel Volcanic Zone. This study provides an enhanced chronology for pyroclastic volcanism of the TgaVC with four locally widespread units named and defined as follows: Welcome Bay and Wharo ignimbrites (together formerly known as Lower Pāpāmoa Ignimbrite); Otawera Ignimbrite; and Arateka Ignimbrite (formerly known as Upper Pāpāmoa Ignimbrite). These eruptives were followed by the eruption of the large-volume Waiteariki Ignimbrite at 2.1 Ma. In northern Hawke’s Bay (150-170 km southeast of TgaVC), several distal tephra-fall horizons and an ignimbrite (Hikuroa Pumice Member) are preserved in marine-hosted sediments and are stratigraphically equivalent to the five ignimbrites of the TgaVC. Using new major- and trace-element data on glass in conjunction with new zircon-derived U-Pb ages, a correlation between the Hawke’s Bay tephras and the TgaVC ignimbrites is established and the Hikuroa Pumice Member is confirmed as the distal deposit of the Waiteariki Ignimbrite. The integrated proximal and distal records show that at least eight eruptions occurred in the TgaVC between 2.4 and 1.9 Ma and provide a maximum repose period between explosive eruptions of ca. 50 kyrs.

year: 2022-09

title: In defence of mātauranga Māori: A response to the 'seven academics'

authors: Waitoki, Waikaremoana

abstract: On 28 July 2021, a group of academics from the University of Auckland published a letter in the Listener, a well-known, non-academic magazine. The letter writers expressed their moral outrage that the Government’s NCEA curriculum working group proposed that science would be taught to Māori students along with its colonising history.

text: In defence of mātauranga Māori: A response to the 'seven academics' On 28 July 2021, a group of academics from the University of Auckland published a letter in the Listener, a well-known, non-academic magazine. The letter writers expressed their moral outrage that the Government’s NCEA curriculum working group proposed that science would be taught to Māori students along with its colonising history.

year: 2022-04-01