which was followed by the late Oligocene faulting that lifted Otago above sea level. Studies of the group were previously constrained by gaps in age mapping. A pretty comprehensive age mapping now exists and gives us ages from 25 million to approximately 9 million years ago. There are for some of the data age inconsistencies, but others appear to be very accurate. There is a general age trend with west being oldest. The Crater near Middlemarch, now the high-level vent diatreme facies of an approximately wide maar is the oldest dated component at 24.8 ± 0.6 Ma. The oldest eruptions of the Dunedin Volcano are likely to have been near Allans Beach on the Otago Peninsula at 16.0 ± 0.4 Ma. Mount Cargill is accurate at 11 Ma before present on multiple samples and techniques. About two-thirds of the eruptions in the entire group took place in the period between 16 to 11 Ma which contains all the Dunedin Volcano eruptions as well. The youngest ages might be as recent as 8 Ma and are at Lookout Bluff, but are still regarded as provisional as corrections may be necessary. The basaltic monogenetic volcanoes were arbitrarily separated from the Dunedin Volcano as found by subsequent detailed rock analysis. However, the Dunedin volcanic group basalts are probably derived from several subtly different isotopic reservoirs. Other long standing knowledge such as the occurrence of rhönite, a very rare mineral, with the minerals phonolite and trachyte in the Dunedin Volcano, confused matters historically until international collaboration with detailed analysis of samples from the whole group area clarified matters. The likely central vent at Port Chalmers, which is likely a large diatreme is filled now with breccia in an oval about 1.3 by 2.5 km that contains volcanic clasts of mainly phonolite but also basanite, basaltic-trachyandesite, trachyandesite, syenite, gabbro, pyroxenite, and hornblendite as well as fragments of Otago Schist and Cenozoic sedimentary rocks. Within the Dunedin Volcano area at Hoopers Inlet are nepheline syenite plutonic dykes but there are no other plutonic rocks in the group area. The Dunedin Volcano has been well studied from the 1880s since New Zealand's first school of geology was established at the University of Otago but detailed studies of north - central volcanoes such as The Crater near Middlemarch were done much later. Northwest of Dunedin the Yellow Hill-Summer Hills area has scoria, tuff and basanite overlying Eocene-Oligocene marine