7. Deep Sea Drilling on the Ninetyeast Ridge: Synthesis and a Tectonic Model
- J.R. Heirtzler,
- H.M. Bolli,
- T.A. Davies,
- J.B. Saunders and
- J.G. Sclater
Published Online: 23 MAR 2013
Copyright © 1977 by the American Geophysical Union.
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
- Published Online: 23 MAR 2013
- Published Print: 1 JAN 1977
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.