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The geological significance of some Triassic microfossils from the South Orkney Islands, Scotia Ridge

Published online by Cambridge University Press:  01 May 2009

I. W. D. Dalziel ,
D. H. Elliot ,
D. L. Jones ,
J. W. Thomson ,
M. R. A. Thomson ,
N. A. Wells  and
W. J. Zinsmeister
I. W. D. Dalziel
Affiliation:
Lamont Doherty Geological Observatory, Columbia University, New York, NY 10027
D. H. Elliot
Affiliation:
Institute of Polar Studies and Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210
D. L. Jones
Affiliation:
US Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
J. W. Thomson
Affiliation:
British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 0ET, U.K.
M. R. A. Thomson
Affiliation:
British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 0ET, U.K.
N. A. Wells
Affiliation:
Institute of Polar Studies and Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210
W. J. Zinsmeister
Affiliation:
Institute of Polar Studies and Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio 43210
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Summary

Late Triassic Radiolaria have been recovered from a bedded chert collected early in 1977 in the South Orkney islands. This is the first reliable palaeontological evidence for the age of the so-called basement complex that forms most of the exposed rock of a microcontinent on the southern limb of the Scotia Ridge. The fossils place a lower limit on the age of deformation of at least part of the complex as post-Karnian or Norian. The basement is overlain by undeformed Jurassic to Cretaceous conglomerates, which suggests this event took place during the early Mesozoic Gondwanian orogeny.

The new data are consistent with the interpretation that the basement complex of the South Orkney Islands represents part of a subduction complex and was accreted to the Pacific margin of Gondwanaland during the late Triassic or early Jurassic time.

Type
Articles
Information
Geological Magazine , Volume 118 , Issue 1 , January 1981 , pp. 15 - 25
Copyright
Copyright © Cambridge University Press 1981

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