The "Waipapa Terrane", North Island, New Zealand : Subdivision and correlation(MEMORIAL VOLUME TO THE LATE PROFESSOR TERUHIKO SAMESHIMA)

Waipapa terrane is the exposed basement of much of the central and northern North Island; it has in the past not been readily correlated with any of the terranes recognised in the South Island and southern North Island. Available information about the lithologies and age relations of rocks in the Waipapa terrane are summarised and three -possibly four - different geographically discrete tectonostratigraphic units, correlated with South Island terranes, are recognised : Omahuta-Puketi area ( = Caples terrane) containing volcanogenic greywackes and laminated argillites, cherts, basaltic tuffs and volcanics of Late Paleozoic age, metamorphosed to prehnite-pumpellite and pumpellite-actinolite facies and uplifted before Mid Jurassic. Bay of Islands - northern Waipapa area ( = Older Torlesse/Rakaia subterrane) of feldspathic sandstones exposed in western Bay of Islands and interleaved with argillites and lithic sandstones in the eastern Bay of Islands. Permian microfossils occur in some terrigenous argillites and in tectonically interleaved oceanic limestones and cherts. Compared with the extent of the South Island Rakaia subterrane the northern Torlesse is a very thin sequence; it is believed that the Torlesse has been tectonically thinned out by a series of imbrication zones parallel to Northland Peninsula and does not extend further to the north of New Zealand. Helena Bay-Hunuas and Moehau-Morrinsville areas which both contain sediments of Upper Jurassic to ? Cretaceous in age, although precise ages and hence stratigraphic relationships are unknown; they are correlated with the Younger Torlesse or Pahau subterrane. However, there are significant differences between the areas : Helena Bay-Hunua rocks are a turbidite sequence containing volcaniclastic sandstones and interleaved basaltic and associated oceanic sedimentary material of Triassic-Jurassic age. Moehau-Morrinsville rocks are dominated by coarser sandstones and argillite conglomerates and lack oceanic material; they are tentatively interpreted as a terrane collision facies blanketing zones of imbrication and younger than the Helena Bay-Hunuas facies. Use of the term Waipapa terrane should be discontinued and Caples, Older Torlesse ( Rakaia subterrane) and Younger Torlesse ( Pahau subterrane) used instead.publishe