Tectonic significance of Late Cretaceous Radiolaria from the obducted Matakaoa volcanics,East Cape,North Island,New Zealand (鮫島輝彦先生追悼論文集)

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Radiolarian faunas from several localities in the Matakaoa Volcanics of the Mangaroa Range, North Island, New Zealand indicate Late Cretaceous (Campanian to Maastrichtian) ages. This contrasts with Late Paleocene/Early Eocene ages obtained from foraminifera approximately 3 km higher in the section. The radiolarian faunas are cosmopolitan and may have been deposited at mid to high latitude. A new structural analysis indicates that the fossils occur in a sequence of intercalated pillow lavas, sediments and dolerites about 10 km thick equivalent of layer 2B of the oceanic crust. This great thickness implies that there has been much repetition by shortening deformation. Layering dips steeply; younging is generally to the north and the sequence is affected by km-scale steeply plunging folds associated with decollements. Structural development involved first formation of melange, and subsequent refolding of these structures to give the present dextral, steeply plunging folds. It is not clear yet how another phase of deformation, steepening and overturning of layering in the Matakaoa Volcanics, relates to these two tectonic events.
静岡大学の論文