TECTONIC AND PALEOBIOGEOGRAPHIC SIGNIFICANCE OF RADIOLARIAN MICROFAUNAS IN THE PERMIAN TO MESOZOIC BASEMENT ROCKS OF THE NORTH-ISLAND, NEW-ZEALAND

From the terranes sutured to the New Zealand Gondwana margin in mid-Cretaceous time, the Murihiku, Waipapa, Torlesse and Mata River terranes have yielded tectonically and paleogeographically significant radiolarian faunas. A late Jurassic fauna from the Murihiku forearc terrane is more cosmopolitan than coeval faunas from the Waipapa. Faunas from the terranes east of the Murihiku, which all show evidence of accretion tectonics, can be subdivided into ocean floor assemblages and assemblages of terrigenous clastic deposits. Waipapa ocean floor assemblages are typically Tethyan while the terrigenous clastic assemblages are non-Tethyan, possibly of southern hemisphere high latitude origin. Ocean floor assemblages show the same eastward younging trends, opposed to the westward sedimentological younging, due to imbrication, as do the assemblages of the terrigenous clastics, but are always a few tens of million years older. Radiolarians from ophiolites (Tangihua Volcanics and Matakaoa Volcanics) indicate that significant portions of the ocean floor obducted onto New Zealand in late Oligocene to earliest Miocene time were of Late Cretaceous to Early Tertiary age.