New Zealand Journal of Geology and Geophysics abstracts

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Radiolarians in offscraped seamount fragments, Aorangi Range, New Zealand

ANNETTE D. GEORGE

Research School of Earth Sciences
Victoria University of Wellington
P.O. Box 600,
Wellington New Zealand*

*Present address: Department of Geology, The University of Western Australia, Nedlands, W.A. 6009, Australia.

Abstract Well-preserved radiolarians occur in coloured argillites at two localities in the Torlesse Terrane exposed in the Aorangi Range in the southernmost part of the North Island, New Zealand. The coloured argillites which host the radiolarians are associated with metabasite, and together these rocks are interpreted as remnants of seamounts which were dismembered immediately before or during subduction and accretion. Recent studies have shown that radiolarian faunas are highly useful for dating such oceanic deposits, and for constraining the depositional ages of adjacent turbidites in terranes which are typically sparsely fossiliferous. Radiolarians from the two Aorangi Range localities are consistent with the Late Jurassic to Early Cretaceous age established by regional age constraints, although one genus previously considered to be exclusively Late Cretaceous is also present. This suggests that radiolarian biostratigraphic zones defined by Northern Hemisphere studies should not be rigidly applied to rocks preserved in Southern Hemisphere terranes until radiolarian stratigraphic ranges for these terranes are adequately established.

Keywords radiolarian dating; seamount; Torlesse Terrane; turbidites; metabasite; Early Cretaceous; Aorangi Range; Cape Palliser; biogeography

Received 24 March 1992; published 25 June 1993
New Zealand Journal of Geology & Geophysics, 1991, Vol. 36: 185—199
0028Ð8306/06/3602—0185 ©The Royal Society of New Zealand 1991

PDF file of entire paper: medium quality (6241K); (scanned from paper original: notes about this process). Digitisation of this article from the printed journal was kindly facilitated by the Geological Society of New Zealand

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