7. Deep Sea Drilling on the Ninetyeast Ridge: Synthesis and a Tectonic Model

  1. J.R. Heirtzler,
  2. H.M. Bolli,
  3. T.A. Davies,
  4. J.B. Saunders and
  5. J.G. Sclater
  1. Bruce P. Luyendyk

Published Online: 23 MAR 2013

DOI: 10.1029/SP009p0165

Indian Ocean Geology and Biostratigraphy

Indian Ocean Geology and Biostratigraphy

How to Cite

Luyendyk, B. P. (1977) Deep Sea Drilling on the Ninetyeast Ridge: Synthesis and a Tectonic Model, in Indian Ocean Geology and Biostratigraphy (eds J.R. Heirtzler, H.M. Bolli, T.A. Davies, J.B. Saunders and J.G. Sclater), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP009p0165

Author Information

  1. Department of Geological Sciences, University of California, Santa Barbara, California 93106

Publication History

  1. Published Online: 23 MAR 2013
  2. Published Print: 1 JAN 1977

ISBN Information

Print ISBN: 9780875902081

Online ISBN: 9781118664919



Legs 22 and 26 of the Deep Sea Drilling Project drilled five sites on the Ninetyeast Ridge. Four main observations emerged:

1) The Ridge has an extrusive volcanic basement with a distinctive petrochemistry.

2) The Ridge is older to the north, ranging from Campanian or older at 90°N to Eocene-Oligocene at 310°S. This age gradient is in the same sense as that for the Indian basin to the west, implying that the Ridge belongs, tectonically, to the Indian plate.

3) It was formed in shallow water, sometimes subaerially, and subsided with time in accordance with known age-depth curves.

4) The Ninetyeast Ridge was formed in more southerly latitudes and has since been transported northwards.

These observations, combined with other geophysical data, show that the Ridge is primarily a sunken oceanic island and seamount chain. Reconstructions based on a fixed hot spot assumption demonstrate strong support for this point source model. The model predicts that the Ridge is from 90 to 20 m.y. old and was formed primarily from volcanism associated with a source beneath the Amsterdam-St. Paul islands, but contributions from a source beneath Kerguelen are also probable. The Kerguelen source mainly generated the Broken Ridge and Naturaliste Plateau, and the Kerguelen Plateau between >100 and 80 mybp.