| Waiareka-Deborah volcanic field | |
|---|---|
| Stratigraphic range: | |
| Type | Igneous |
| Overlies | Rakaia Terrane |
| Area | 890 square kilometres (340 sq mi)[1] |
| Lithology | |
| Primary | Sub-alkaline basalt and basaltic andesite |
| Location | |
| Coordinates | 45°00′S 170°18′E / 45.0°S 170.3°E |
| Region | Otago |
| Country | New Zealand |
| Type section | |
| Named for | Waiareka Valley, inland from Oamaru |
 Map of surface volcanic features of the South Island centred near Oamaru. The basalts of the Waiareka-Deborah volcanic field are more red tinted than those of the Dunedin volcanic group.
Clicking on the map enlarges it, and enables panning and mouseover of volcano name/wikilink and ages before present. Key for the volcanics that are shown with panning is: basalt (shades of brown/orange), monogenetic basalts, undifferentiated basalts, arc basalts, arc ring basalts, olivine (basalts shades of olive), phonolite (pale salmon), dacite, andesite (shades of red), basaltic andesite, rhyolite, (ignimbrite is lighter shades of violet), and plutonic or intusive (gray) - so dolerite/diabase/microgabbro will have shadings towards gray compared to erupted basalt. | |
The Waiareka-Deborah volcanic field is a group of sub-alkaline basalt to basaltic andesite composition volcanics, most of which erupted about 34 million years ago. There is a range of determined ages by various methods and sites although most have very similar timings. At Bridge Point one deposit has an age of 39.5 ± 1.8 and another 34.3 ± 0.5 million years ago.[1] They are found near Oamaru, South Island New Zealand,[1] and are small Surtseyan volcanoes that erupted originally on a submerged continental shelf.[2][3]
The former term, the Waiareka-Deborah volcanic group should not be used as any alkali basalt volcanoes in this group and all of those in the former Waiareka volcanic field are now assigned to the Dunedin volcanic group and its monogenetic volcanic field.[4]
- ^ a b c d Scott, James M.; White, James D. L.; le Roux, Petrus J. (2020). "Intraplate volcanism on the Zealandia Eocene-Early Oligocene continental shelf: The Waiareka-Deborah Volcanic Field, North Otago". New Zealand Journal of Geology and Geophysics. 63 (4): 450–468. doi:10.1080/00288306.2020.1785896. S2CID 221380814.
- ^ Simone Hicks, PhD proposal: Ecological and sedimentological evolution of the volcanically active Oligocene continental shelf, east Otago, New Zealand, Geology Department, University of Otago. Retrieved 19 April 2010.
- ^ R. A. F. Cas; C. A. Landis; R. E. Fordyce (1989). "A monogenetic, Surtla-type, Surtseyan volcano from the Eocene-Oligocene Waiareka-Deborah volcanics, Otago, New Zealand: A model". Bulletin of Volcanology. 51 (4): 281–298. Bibcode:1989BVol...51..281C. doi:10.1007/BF01073517. S2CID 129657592.
- ^ Scott, James M.; Pontesilli, Alessio; Brenna, Marco; White, James D. L.; Giacalone, Emanuele; Palin, J. Michael; le Roux, Petrus J. (2020). "The Dunedin Volcanic Group and a revised model for Zealandia's alkaline intraplate volcanism". New Zealand Journal of Geology and Geophysics. 63 (4): 510–529. doi:10.1080/00288306.2019.1707695. S2CID 212937447.