Abstract:
Two classes of basement rock are recognised on the Campbell Plateau: silicic to intermediate plutonic rocks, and quartzose metasedimentary rocks. The plutonic rocks, from Auckland Island and petroleum exploration wells Pakaha-1, Tara-1, and Pukaki-1, are petrologically similar to granites from southern Stewart Island, Snares Islands, and western South Island and produce similar Cretaceous K-Ar ages. Granodiorite from Bounty Island (K-Ar age 189 Ma) is petrologically comparable with rocks in the Foveaux Strait area. Metasedimentary rocks from Campbell Island, the sea floor near Bounty Islands, and petroleum wells Kawau-1A, Hoiho-1C, and possibly Rakiura-1, are comparable with early Paleozoic metasedimentary rocks (e.g., Greenland Group) on the West Coast of the South Island, as well as Robertson Bay Group of northern Victoria Land and other Antarctic suites, and basement from DSDP hole 281 on the South Tasman Rise. They are distinct compositionally from late Paleozoic and Mesozoic metasedimentary rocks of eastern New Zealand (Caples and Torlesse terranes). Magnetic anomalies on the Campbell Plateau (Campbell Magnetic Anomaly System) have previously been correlated with the Stokes Magnetic Anomaly System. Since Caples and Torlesse rocks lie immediately north and east of the Stokes Magnetic Anomaly System throughout onshore New Zealand, but quartzose metasedimentary rocks occur both south and north of the Campbell Magnetic Anomaly System on the Campbell Plateau, these anomaly systems cannot follow the same tectonic terrane boundaries. Therefore the Campbell Magnetic Anomaly System should not be correlated with the Stokes Magnetic Anomaly System, weakening the basis for the Campbell Fault, which has been postulated to offset the two anomaly systems.