Skip to main content
SpringerLink
Log in

Morphology and tectonics of the Australian-Antarctic Discordance between 123° E and 128° E

  • Published:
Marine Geophysical Researches Aims and scope Submit manuscript

Abstract

The Australian-Antarctic Discordance (AAD) is an anomalously deep and rugged zone of the Southeast Indian Ridge (SEIR) between 120° E and 128° E. The AAD contains the boundary between the Indian Ocean and Pacific Ocean isotopic provinces. We have analyzed SeaMarc II bathymetric and sidescan sonar data along the SEIR between 123° E and 128° E. The spreading center in the AAD, previously known to be divided into several transform-bounded sections, is further segmented by nontransform discontinuities which separate distinct spreading cells. Near the transform which bounds the AAD to the east, there is a marked change in the morphology of the spreading center, as well as in virtually every measured geochemical parameter. The spreading axis within the Discordance lies in a prominent rift valley similar to that observed along the Mid-Atlantic Ridge, although the full spreading rate within the AAD is somewhat faster than that of slow-spreading centers (~ 74 mm a−1 vs. 0–40 mm a−1). The AAD rift valleys show a marked contrast with the axial high that characterizes the SEIR east of the AAD. This change in axial morphology is coincident with a large (~ 1 km) deepening of the spreading axis. The segmentation characteristics of the AAD are analogous to those of the slow-spreading Mid-Atlantic Ridge, as opposed to the SEIR east of the AAD, which exhibits segmentation characteristics typical of fast-spreading centers. Thus, the spreading center within and east of the AAD contains much of the range of global variability in accretionary processes, yet it is a region free from spreading rate variations and the volumetric and chemical influences of hotspots. We suggest that the axial morphology and segmentation characteristics of the AAD spreading centers are the result of the presence of cooler than normal mantle. The presence of a cool mantle and the subsequent diminution of magma supply at a constant spreading rate may engender the creation of anomalously thick brittle lithosphere within the AAD, a condition which favor, the creation of an axial rift valley and of thin oceanic crust, in agreement with petrologic studies. The morphologies of transform and non-transform discontinuities within the Discordance also possess characteristics consistent with the creation of anomalously thick lithosphere in the region. The upper mantle viscosity structure which results from lower mantle temperatures and melt production rates may account for the similarity in segmentation characteristics between the AAD and slow-spreading centers. The section of the AAD which overlies the isotopic boundary is associated with chaotic seafloor which may be caused by an erratic pattern of magmatism and/or complex deformation associated with mantle convergence. Finally, the pattern of abyssal hill terrain within a portion of the AAD supports previous models for the formation of abyssal hills at intermediate- and slow-spreading ridges, and provides insights into how asymmetric spreading is achieved in this region.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  • Alvarez, W., 1982, Geological evidence for the geographical pattern of mantle return flow and the driving mechanism of plate tectonics,J. Geophys. Res. 87, 6697–6710.

    Google Scholar 

  • Alvarez, W., 1990, Geological evidence for the plate driving mechanism: The continental undertow hypothesis and the Australian Antarctic Discordance,Tectonics 9, 1213–1220.

    Google Scholar 

  • Anderson, R. N., Spariosu, D. J., Weissel, J.K., and Hayes, D. E., 1980, The interrelation between variations in magnetic anomaly amplitudes and basalt magnetization and chemistry along the Southeast Indian Ridge,J. Geophys. Res. 85, 3883–3898.

    Google Scholar 

  • Blackington, J. G., Hussong, D. M., and Kosalos, J., 1983, First results from a combination of side-scan sonar and seafloor mapping system (SeaMARC II), inOffshore Technology Conference, OTC 4478, pp. 307–311.

  • Bonatti, E., 1978, Vertical tectonism in oceanic fracture zones,Earth Planet. Sci. Lett. 37, 369–379.

    Google Scholar 

  • Chen, Y. and Morgan, W. J., 1990, Rift valley/no rift valley transition at mid-ocean ridges,J. Geophys. Res. 95, 17,571–17,581.

    Google Scholar 

  • Chen, Y. and Morgan, W. J., 1990, A non-linear rheology model for mid-ocean ridge axis topography,J. Geophys. Res. 95, 17,583–17,604.

    Google Scholar 

  • Christie, D. M., Pyle, D., Sempéré, J.-C., Phipps Morgan, J., and Shor, A., 1988, Petrologic and tectonic observations in and adjacent to the Australian-Antarctic Discordance (abstract),EOS Trans. AGU 69, 1426.

    Google Scholar 

  • Cochran, J. R., 1986, Variations in subsidence rates along intermediate and fast spreading mid-ocean ridges,Geophys. J. R. Astron. Soc. 87, 421–545.

    Google Scholar 

  • Duncan, R. A., 1981, Hotspots in the southern oceans — An absolute frame of reference for motion of the Gondwana continents,Tectonophysics 74, 29–42.

    Google Scholar 

  • Embley, R. W., Kulm, L. D., Massoth, G., Abbott, D., and Holmes, M., 1987, Morphology, structure and resource potential of the Blanco Transform Fault Zone, In Scholl, D. W., Grantz, A., and Yedder, J. G., editors, Geology and Resource Potential of the Continental Margin of Western North America and Adjacent Ocean Basins — Beaufort Sea to Baja, California, volume 6 of Earth Science Series, pages 549–561. Circum-Pacific Council for Energy and Mineral Resources.

  • Fornari, D. J., Gallo, D. G., Edwards, M. H., Madsen, J. A., Perfit, M. R., and Shor, A. N., 1989, Structure and topography of the Siqueiros transform fault system: Evidence for the development of intra-transform spreading centers,Mar. Geophys. Res. 11, 263–299.

    Google Scholar 

  • Forsyth, D. W., 1992, Geophysical constraints on mantle flow and melt generation beneath mid-ocean ridges, In Phipps Morgan, J., Blackman, D., and Sinton, J. (eds.)Mantle Flow and Melt Migration beneath Mid-Ocean Ridges, (in press).

  • Forsyth, D. W., Ehrenbard, R. L., and Chapin, S., 1987, Anomalous upper mantle beneath the Australian-Antarctic Discordance,Earth Planet. Sci. Lett. 84, 471–478.

    Google Scholar 

  • Fox, P. J. and Gallo, D. G., 1984, A tectonic model for ridge-transform-ridge plate boundaries: Implications for the structure of oceanic lithosphere,Tectonophysics,104, 205–242.

    Google Scholar 

  • Gallo, D. G., Kidd, W. S. F., Fox, P. J., Karson, J. A., Macdonald, K. C., Crane, K., Choukroune, P., Seguret, M., Moody, R., and Kastens, K., 1984, Tectonics at the intersection of the East Pacific Rise with the Tamayo Transform Fault,Mar. Geophys. Res. 6, 159–186.

    Google Scholar 

  • Gallo, D. G., Fox, P. J., and Macdonald, K. C., 1986, A Sea Beam investigation of the Clipperton Transform Fault: The morphotectonic expression of a fast slipping transform boundary.J. Geophys. Res. 91 (B3), 3455–3467.

    Google Scholar 

  • Graham, D., Lupton, J., Klein, E., Christie, D., and Pyle, D., 1990, Helium isotope geochemistry of the Australian-Antarctic Discordance, In Proc. 7th Int. Conf. of Geochronology, Cosmochronology and Isotope Geology, Canberra.

    Google Scholar 

  • Grindlay, N. R., Fox, P. J., and Macdonald, K. C., 1991, Secondorder discontinuities in the South Atlantic: Morphology, structure, and evolution,Mar. Geophys. Res. 13, 21–50.

    Google Scholar 

  • Hayes, D. E., 1976, Nature and implications of asymmetric spreading — different rates for different plates,Geol. Soc. Am. Bull. 87, 994–1002.

    Google Scholar 

  • Hayes, D. E., 1988, Age-dependent relationships and depth anomalies in the southeast Indian Ocean and South Atlantic Ocean,J. Geophys. Res. 93 (B4), 2937–2954.

    Google Scholar 

  • Hayes, D. E. and Conolly, J. R., 1972, Morphology of the Southeast Indian Ocean, In Hayes, D. E. (ed.),Antarctic Oceanology II: the Australian-New Zealand Sector, volume 19 of Antarctic Res. Ser., pp. 225–245. Am. Geophys. Union.

  • Kappel, E. S. and Ryan, W. B. F., 1986, Volcanic episodicity and a non-steady state rift valley along Northeast Pacific spreading centers: Evidence from SeaMARC I,J. Geophys. Res. 91, 13,925–13,940.

    Google Scholar 

  • Karson, J. A. and Dick, H. J. B., 1983, Tectonics of ridge transform intersections at the Kane Fracture Zone,Mar. Geophys. Res. 6, 51–98.

    Google Scholar 

  • Klein, E. M. and Langmuir, C. H., 1987, Global correlations of ocean ridge basalt chemistry with axial depth and crustal thicknesses,J. Geophys. Res. 92, 8089–8115.

    Google Scholar 

  • Klein, E. M., Langmuir, C. H., and Staudigel, H., 1991, Geochemistry of basalts from the Southeast Indian Ridge, 115°–138° E,J. Geophys. Res. 96, 2089–2108.

    Google Scholar 

  • Klein, E. M., Langmuir, C. H., Zindler, A., Staudigel, H., and Hamelin, B., 1988, Isotope evidence of a mantle convection boundary at the Australian-Antarctic Discordance,Nature 333, 623–629.

    Google Scholar 

  • Kuo, B. Y. and Forsyth, D. W., 1988, Gravity anomalies of the ridge-transform system in the South Atlantic between 31° and 34.5° S: Upwelling centers and variations in crustal thickness,Mar. Geophys. Res. 10, 202–232.

    Google Scholar 

  • Lachenbruch, A. H., 1973, Dynamics of a passive spreading center,J. Geophys. Res. 78, 3395–3417.

    Google Scholar 

  • Lin, J., Purdy, G. M., Schouten, H., Sempéré, J.-C., and Zervas, C. E., 1990. Evidence from gravity data for focused magmatic accretion along the Mid-Atlantic Ridge,Nature 344, 627–632.

    Google Scholar 

  • Lin, J. and Phipps Morgan, J., 1992, The spreading rate dependence of three-dimensional mid-ocean ridge gravity structure,Geophys. Res. Lett. 19, 13–16.

    Google Scholar 

  • Macdonald, K. C., 1982, Mid-ocean ridges: Fine scale tectonic, volcanic and hydrothermal processes within the plate boundary zone,Annu. Rev. Earth Planet. Sci. 10, 155–190.

    Google Scholar 

  • Macdonald, K. C., 1986, The crest of the Mid-Atlantic Ridge, In Vogt, P. R., and Tuckholke, B. E. (eds.),The Geology of North America, Volume M, the Western North Atlantic Region. Geological Society of America.

  • Macdonald, K. C., Fox, P. J., Perram, L. J., Eisen, M. F., Haymon, R. M., Miller, S. P., Carbotte, S. M., Cormier, M.-H., and Shor, A. N., 1988, A new view of the mid-ocean ridge from the behaviour of ridge axis-discontinuities,Nature 335, 217–225.

    Google Scholar 

  • Madsen, J. A., Forsyth, D. W., and Detrick, R. S., 1984, A new isostatic model for the East Pacific Rise crest,J. Geophys. Res. 89, 9997–10,016.

    Google Scholar 

  • Marks, K. M., 1990. Geophysical Investigation of the Australian-Antarctic Discordance Zone, PhD thesis, University of Houston.

  • Marks, K. M., Vogt, P. R., and Hall, S. A., 1990, Residual depth anomalies and the origin of the Australian-Antarctic Discordance Zone,J. Geophys. Res. 95, 17,325–17,337.

    Google Scholar 

  • Menard, H. W. and Atwater, T., 1969, Origin of fracture zone topography,Nature 222, 1037–1040.

    Google Scholar 

  • Minster, J.-B. and Jordan, T. H., 1978, Present-day plate motions,J. Geophys. Res. 83, 5331–5354.

    Google Scholar 

  • OTTER, 1984, The geology of the Oceanographer Transform: The ridge-transform intersection,Mar. Geophys. Res. 6, 109–141.

    Google Scholar 

  • 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 

  • Phillips, J. D. and Fleming, H. S., 1978, Multi-beam sonar study of the Mid-Atlantic Ridge rift valley, 36°–37° N, Geological Society of America, MC-19.

  • Phipps Morgan, J. and Forsyth, D. W., 1988, Three-dimensional flow and temperature perturbations due to a transform offset: Effects of oceanic crustal and upper mantle structure,J. Geophys. Res. 93, 2955–2966.

    Google Scholar 

  • Phipps Morgan, J. and Parmentier, E. M., 1984, Lithospheric stress near a ridge-transform intersection,Geophys. Res. Lett. 11, 113–116.

    Google Scholar 

  • Phipps Morgan, J., Parmentier, E. M., and Lin, J., 1987, Mechanisms for the origin of mid-ocean ridge axial topography: Implications for the thermal and mechanical structure of accreting plate boundaries,J. Geophys. Res. 92, 12,823–12,836.

    Google Scholar 

  • Phipps Morgan, J., Sempéré, J.-C., Christie, D., and Shor, A., 1988, Propagating rifts along the Southeast Indian Ridge (abstract),EOS Trans. AGU 69, 1430.

    Google Scholar 

  • Pockalny, R. A., Detrick, R. S., and Fox, P. J., 1988, Morphology and tectonics of the Kane Transform from Sea Beam bathymetry data,J. Geophys. Res. 93, 3179–3193.

    Google Scholar 

  • Pyle, D., Christie, D., and Mahoney, J., 1992, Resolving an isotope boundary in the Australian-Antarctic Discordance,Earth Planet. Sci. Lett. (in press).

  • Rabinowicz, M., Rouzo, S., Sempéré, J.-C., and Rosemberg, C., 1992, Three-dimensional mantle flow beneath mid-ocean ridges,J. Geophys. Res. (in press).

  • Searle, R. C., 1989, Location and segmentation of the Cocos-Nazca spreading centre west of 95° W,Mar. Geophys. Res. 11, 15–26.

    Google Scholar 

  • Sempéré, J.-C., Purdy, G. M., and Schouten, H., 1990, The segmentation of the Mid-Atlantic Ridge between 24°00′ N and 30°40′ N,Nature 344, 427–431.

    Google Scholar 

  • Sempéré, J.-C., Palmer, J., Phipps Morgan, J., Christie, D. M., and Shor, A. N., 1991, The Australian-Antarctic Discordance,Geology 19, 429–432.

    Google Scholar 

  • Sempéré, J.-C., Lin, J., Brown, H., Schouten, H., and Purdy, G. M., 1993, The Mid-Atlantic Ridge between 24°00′ N and 30°40′ N: Along-axis morphotectonic variations and the segmentation of the spreading center,Mar. Geophys. Res. (in press).

  • Sender, K. L., Shor, A. N., and Hagen, R., 1989, SeaMARC II sidescan processing techniques (abstract),EOS Trans. AGU 70, 1304.

    Google Scholar 

  • Severinghaus, J. and Macdonald, K. C., 1988, High inside corners at ridge-transform intersections,Mar. Geophys. Res. 9, 353–367.

    Google Scholar 

  • Stein, S., Melosh, H. J., and Minster, J.-B., 1977, Ridge migration and asymmetric seafloor spreading,Earth Planet. Sci. Lett. 36, 51–62.

    Google Scholar 

  • Stewart, W. K., 1988, Multisensor modeling underwater with uncertain information, PhD thesis, MIT/WHOI Joint Program.

  • Tamsett, D. and Searle, R., 1988, Structure and development of the mid-ocean ridge plate boundary in the Gulf of Aden: Evidence from GLORIA side-scan sonar,J. Geophys. Res. 93, 3157–3178.

    Google Scholar 

  • Tapponnier, P. and Francheteau, J., 1978, Necking of the lithosphere and the mechanics of slowly accreting plate boundaries,J. Geophys. Res. 83, 3955–3970.

    Google Scholar 

  • Tyce, R. C., 1987, Deep seafloor mapping systems — a review,Mar. Tech. Soc. Jnl. 20, 4–16.

    Google Scholar 

  • Veevers, J. J., 1982, Australian-Antarctic Depression from the midocean ridge to adjacent continents,Nature 295, 315–317.

    Google Scholar 

  • Veevers, J. J., McA, C., Power, A. and Roots, S. R., 1991, Review of seafloor spreading around Australia, I. Synthesis of the patterns of spreading,Aus. J. Ear. Sci. 38, 373–389.

    Google Scholar 

  • Vogt, P. R., Cherkis, N. Z., and Morgan, G. A., 1984, Project Investigator-I: Evolution of the Australian-Antarctic Discordance from a detailed aeromagnetic study, In Oliver, R. L., James, P. R., and Jago J, (eds.),Antarctic Earth Science: Proceedings 4th International Symposium on Antarctic Earth Science, Canberra, Australian Academy of Science.

  • Vogt, P. R. and Johnson, G. L., 1973, A longitudinal seismic reflection profie of the Reykjanes Ridge: Part II — Implications for the mantle hotspot hypothesis,Earth Planet. Sci. Lett. 18, 49–58.

    Google Scholar 

  • Weissel, J. K. and Hayes, D., 1971, Asymmetric seafloor spreading south of Australia,Nature 231, 518–522.

    Google Scholar 

  • Weissel, J. K. and Hayes, D., 1974, The Australian-Antarctic Discordance: New results and implications,J. Geophys. Res. 197, 2579–2587.

    Google Scholar 

  • Woodhouse, J. H., and Dziewonski, A. M., 1984, Mapping the upper mantle: Three-dimensional modeling of earth structure by inversion of seismic waveforms,J. Geophys. Res. 89, 5953–5986.

    Google Scholar 

  • Zervas, C. E., 1988. A Finite Element Investigation of Topographic Variation at Mid-Ocean Ridges Spreading at the same Rate, PhD thesis, University of Washington.

  • Zervas, C. E., Sempéré, J.-C., Lin, J., and Purdy, G. M., 1989, A Sea Beam, gravity, and magnetic study of the Atlantis Transform at 30° N on the Mid-Atlantic Ridge,EOS Trans AGU 70, 1305.

    Google Scholar 

Download references

Author information

Author notes

  1. Jeb Palmer

    Present address: Sierra Geophysics, 11255 Kirkland Way, 98033, Kirkland, WA, USA

Authors and Affiliations

  1. School of Oceanography, University of Washington, 98195, Seattle, WA, USA

    Jeb Palmer & Jean-Christophe Sempéré

  2. College of Oceanography, Oregon State University, 97331, Corvallis, OR, USA

    David M. Christie

  3. Institute of Geophysics and Planetary Physics, University of California, 92093, San Diego, La Jolla, CA, USA

    Jason Phipps Morgan

Authors
  1. Jeb Palmer
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jean-Christophe Sempéré
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. David M. Christie
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Jason Phipps Morgan
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

About this article

Cite this article

Palmer, J., Sempéré, JC., Christie, D.M. et al. Morphology and tectonics of the Australian-Antarctic Discordance between 123° E and 128° E. Mar Geophys Res 15, 121–152 (1993). https://doi.org/10.1007/BF01204132

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1007/BF01204132

Key words

Search

Navigation