Radiolarians in offscraped seamount fragments, Aorangi Range, New Zealand

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.

Episodicity of Mesozoic terrane accretion along the Pacific margin of Gondwana: implications for superplume-plate interactions

“…Jurassic to Aptian-Albian argillic and metabasic rocks in the Wellington region, interpreted to be part of a dismembered seamount (George 1993), which are cut by ~99 Ma lamprophyre dikes.…”

Data report: early Late Cretaceous radiolarians from IODP Site U1520 (Expedition 375, Hikurangi subduction margin)

“…Radiolarian biostratigraphy is relatively well resolved in the mid-Cretaceous following extensive studies of onshore sections in Europe, Japan, and North America and offshore studies in the low-latitude Pacific, Indian, and Atlantic Oceans (Sanfilippo and Riedel, 1985;O'Dogherty, 1994). However, there have been very few studies of radiolarian assemblages of this age from the southwest Pacific region (e.g., George, 1993).…”