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Microplankton provide 9 Ma age for sediment in the Macquarie Island ophiolite complex


Quilty, PG and Crundwell, MP and Wise Jr, SW, Microplankton provide 9 Ma age for sediment in the Macquarie Island ophiolite complex, Australian Journal of Earth Sciences, 55, (8) pp. 1119-1125. ISSN 0812-0099 (2008) [Refereed Article]

Copyright Statement

Cooyright 2008 Geological Society of Australia

DOI: doi:10.1080/08120090802266584


Macquarie Island in the southwest Pacific Ocean (558S) is unique as an exposed location for studying oceanic crust generated by slow seafloor spreading—regions where rocks are difficult to date using radiometric methods. Bolboforms, an extinct group of poorly known microplankton, in sediment intercalated with pillow lavas yield tight constraints (9.01–8.78 Ma) on the age of formation of the dominantly seafloor volcanic sequence constituting the south of the island. The occurrence of Bolboforma metzmacheri extends the known geographic range of this Late Miocene zonal marker species in the southwest Pacific. A monospecific calcareous nannoplankton flora (Reticulofenestra perplexa) accompanied by the foraminifer Neogloboquadrina pachyderma in sediment from the north part of the island indicates a slightly older age (9.5–9.3 Ma), consistent with a radiometric date (9.2+0.4 Ma) from nearby volcanics. The new age data indicate that the ocean floor volcanic sequence formed early in the Late Miocene, possibly along short segments of a slow-spreading midocean ridge. Bolboforms have potential to provide fine-scale dating in other similarly complex ridge systems that are difficult to date by other means.

Item Details

Item Type:Refereed Article
Keywords:bolboforms, foraminifers, Macquarie Island, Miocene, nannoplankton, ophiolite
Research Division:Earth Sciences
Research Group:Geology
Research Field:Palaeontology (incl. palynology)
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Quilty, PG (Dr Pat Quilty)
ID Code:94850
Year Published:2008
Web of Science® Times Cited:9
Deposited By:Earth Sciences
Deposited On:2014-09-18
Last Modified:2014-10-07

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