Advertisement

Marine Geophysical Researches

, Volume 11, Issue 1, pp 1–14 | Cite as

The Rodriguez Triple Junction (Indian Ocean): Structure and evolution for the past one million years

  • M. Munschy
  • R. Schlich
Article

Abstract

The Rodriguez Triple Junction (RTJ) corresponds to the junction of the three Indian Ocean spreading ridges. A detailed survey of an area of 90 km by 85 km, centered at 25°30′ S and 70° E, allows detailed mapping (at a scale of 1/100 000) of the bathymetry (Seabeam) and the magnetic anomalies. The Southeast Indian Ridge, close to the triple junction, is a typical intermediate spreading rate ridge (2.99 cm a-1 half rate), trending N140°. The Central Indian Ridge rift valley prolongs the Southeast Indian Ridge rift valley with a slight change of orientation (12°). The half spreading rate and trend of this ridge are 2.73 cm a-1 and N152° respectively. In contrast, the Southwest Indian Ridge close to the triple junction is expressed by two deep-valleys (4300 and 5000 m deep) which abut the southwestcrn flanks of the two other ridges, and appears to be a stretched area without axial neovolcanic zone. The evolution of the RTJ is analysed for the past one million years. The instantaneous velocity triangle formed by the three ridges cannot be closed indicating that the RTJ is unstable. A model is proposed to explain the evolution of the unstable RRF Rodriguez Triple Junction. The model shows that the axis of the Central Indian Ridge is propressively offset from the axis of the Southeast Indian Ridge at a velocity of 0.14 cm a-1, the RTJ being restored by small jumps. This unstable RRF model explains the directions and offsets which are observed in the vicinity of the triple junction. The structure and evolution of the RTJ is similar to that of the Galapagos Triple Junction located in the East Pacific Ocean and the Azores Triple Junction located in the Central Atlantic Ocean.

Key words

oceanic spreading ridge triple junction Indian Ocean 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Atwater, T. and Mudie, J. D., 1973, Detailed Near-Bottom Geophysical Study of the Gorda Rise, J. Geophys. Res. 78, 8665–8668.Google Scholar
  2. Fisher, R. L., Sclater, J. G., and McKenzie, D. P., 1971, Evolution of the Central Indian Ridge, Western Indian Ocean, Geol. Soc. Amer. Bull. 82, 553–562.Google Scholar
  3. Lowrie, W. and Alvarez, W., 1981, One Hundred Million Years of Geomagnetic Polarity History, Geology 9, 392–397.Google Scholar
  4. Macdonald, K. C., 1982, Mid-Ocean Ridges: Fine Scale Tectonic, Volcanic, and Hydrothermal Processes within the Plate Boundary Zone, Ann. Rev. Earth Planet. Sci. 10, 155–190.Google Scholar
  5. Macdonald, K. C., Miller, S. P., Huestis, S. P., and Spiess, F. N., 1980, Three-Dimensional Modelling of a Magnetic Reversal Boundary from Inversion of Deep-Tow Measurements, J. Geophys. Res. 85, 3670–3680.Google Scholar
  6. McKenzie, D. P. and Morgan, W. J., 1969, Evolution of Triple Junctions, Nature 224, 295–315.Google Scholar
  7. McKenzie, D. P. and Sclater, J. G., 1971, The Evolution of the Indian Ocean since the Late Cretaceous, Geophys. J. R. Astr. Soc. 25, 437–528.Google Scholar
  8. Munschy, M., 1987, Etude géophysique détaillée du point triple de Rodriguez et de la zone axiale des trois dorsales associées, Thèse de Doctorat, Univ. L. Pasteur, Strasbourg I.Google Scholar
  9. Parker, R. L. and Huestis, S. P., 1974, The Inversion of Magnetic anomalies in the Presence of Topography, J. Geophys. Res. 79, 1587–1593.Google Scholar
  10. Patriat, P. 1983, Evolution du système de dorsales de l'océan Indien, Thèse Doct. es Sciences, Univ. Curie, Paris.Google Scholar
  11. Patriat, P. and Courtillot, V., 1984, On the Stability of Triple Junctions and its Relation to Episodicity in Spreading, Tectonics 3, 317–332.Google Scholar
  12. Peddie, N. W., 1982, International Geomagnetic Reference Field, 1980: a Report by IAGA Division I Working Group 1, Geophys. J. R. Astr. Soc. 68, 265–268.Google Scholar
  13. Renard, V. et Allenou, J. P., 1979, Le sea-beam sondeur à multi-faisceaux du N/O “Jean Charcot” description, évaluation et premiers résultats, Rev. Hydrog. Intern., Monaco 56, 35–71.Google Scholar
  14. Royer, J. Y., 1985, Evolution cinématique détaillée de la dorsale est-indienne entre le point triple de Rodriguez et les îles Saint Paul et Amsterdam, Thèse de Doctorat, Univ. L. Pasteur, Strasbourg I.Google Scholar
  15. Sander, E. L. and Mrazek, C. P., 1982, Regression Technique to Remove Temporal Variation from Geomagnetic Survey Data, Geophysics 47, 1437–1443.Google Scholar
  16. Schlich, R., 1982, The Indian Ocean: Aseismic Ridges, Spreading Centers, and Oceanic Basins, Nairn, A. E. M., and Stehli, F. G., (eds.), The Ocean basins and margins, 6, The Indian Ocean, New York, Plenum Press, 51–147.Google Scholar
  17. Schlich, R., Munschy, M., Marthelot, J. M., Royer, J. Y., and Schaning, M., 1987, Les campagnes du N.O. Jean Charcot sur le point triple de Rodriguez (océan Indien): premiers résultats, Bull. Soc. Géol. France 3, 693–697.Google Scholar
  18. Schlich, R., Munschy, M., and Blanck, M., 1988, frCartes 0 Bathymétriques, gravimétriques et magnétiques au 1/2000.000 et 1/100.000 du point triple de Rodriguez et de la zone axiale des trois dorsales associées (océan Indien), Institut de Physique du Globe, Strasbourg, France.Google Scholar
  19. Sclater, J. G., Bowin, C., Hey, R., Hoskins, H., Peirce, J., Phillips, J., and Tapscott, C., 1976, The Bouvet Triple Junction, J. Geophys. Res. 81, 1857–1869.Google Scholar
  20. Sclater, J. G., Fischer, R. L., Patriat, P., Tapscott, C., and Parsons, B., 1981, Eocene to Recent Development of the Southwest Indian Ridge, a Consequence of the Evolution of the Indian Ocean Triple Junction, Geophys. J. R. Astr. Soc. 64, 587–604.Google Scholar
  21. Searle, R., 1980, Tectonic Pattern of the Azores Spreading Center and Triple Junction, Earth Planet. Sci. Lett. 51, 415–434.Google Scholar
  22. Searle, R. and Francheteau, J., 1986, Morphology and Tectonics of the Galapagos Triple Junction, Mar. Geophys. Res. 8, 95–129.Google Scholar
  23. Tapscott, C. R., Patriat, P., Fisher, R. L., Sclater, J. G., Hoskins, H., and Parsons, B., 1980, The Indian Ocean Triple Junction, J. Geophys. Res. 85, 4723–4739.Google Scholar
  24. Weissel, J. K., and Hayes, D. E., 1972, Magnetic Anomalies in the Southeast Indian Ocean, in D. E., Hayes, (ed.), Antarctic Oceanology II: The Australian-New Zealand Sector, Antarctic Res. Ser. 19, AGU, Washington, D.C., 165–196.Google Scholar

Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • M. Munschy
    • 1
  • R. Schlich
    • 1
  1. 1.Laboratoire de Géophysique Marine (CNRS UA 323)Institut de Physique du GlobeSTRASBOURG CedexFrance

Personalised recommendations