Abstract
Interpretation of deep seismic reflection data across the Gascoyne Margin reveals six distinct seismic facies units related to the tectono-magmatic breakup history. On the outer Exmouth Plateau four large scale units are identified: (1) an extensively block-faulted upper crust; (2) a middle-crustal unit of discontinuous, undulatory reflectors; (3) a reflection-free deep crustal unit; and (4) a lower-crustal band of low-frequency, high-amplitude reflectors. Two additional units are found near the continent-ocean boundary (COB); (5) seaward-dip** reflectors (SDR); and (6) landward-dip** reflectors in the lower crust below the SDR. The lower-crustal high-reflectivity band, located near the top of a high-velocity unit (Vp > 7 kms−1), is interpreted as magmatic underplating. There is a spatial correlation between the underplated area and the presence of extensive upper-crustal block-faulting and intrusive rocks in the shallow crust. The undulatory middle-crustal reflector unit is also only identified in the outer plateau area, and is interpreted as a zone in which the upper-crustal faults terminate. The inner parts of the margin consist of a deep basin showing little upper-crustal faulting and no evidence of middle crustal deformation or underplating. Theoretical modeling of the effect of rifting and magmatic underplating on crustal strength profiles suggests that the brittle-ductile transition may migrate at least 5 km upwards during several million years after the underplating event. Based on the seismic interpretation and crustal strength modeling we propose that the seismic structure of the outer Exmouth Plateau is severely modified by a transient change in the crustal rheological structure associated with magmatic underplating.
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References
AGSO North West Shelf Study Group: 1994, Deep reflections on the North West Shelf: changing our perceptions of basin formation, AGSO J. Australian Geol. Geophys. 15: 63–75.
Alvestad, E.: 1997, Seismisk karakterisering og dannelse av det ekstrusive oppsprekknings-komplekset på Møre Marginen, Cand. Scient. thesis, University of Oslo, 181 pp.
Anders, M. H. and Sleep, N. H.: 1992, Magmatism and extension: the thermal and mechanical effects of the Yellowstone hotspot, J. Geophys. Res. 47: 15379–15393.
Anderson, D. L., Zhang, Y. S. and Tanimoto, T.: 1992, Plume heads, continental lithosphere, flood basalts and tomography, in B. C. Storey, T. Alabaster and R. J. Pankhurst (eds.), Magmatism and the Causes of Continental Break-up, Geol. Soc. Special Publ. 68: 99–124.
Baillie, P. W. and Jacobson, E. P.: 1997, Prospectivity and exploration history of the Barrow Sub-basin: Western Australia, The APPEA J. 117: 117–135.
Baillie, P. W., Powell, C. McA., Li, Z. X. and Ryall, A. M.: 1994, The tectonic framework of Western Australia's Neoproterozoic to Recent sedimentary basins, in P. G. Purcell and R. R. Purcell (eds.), The Sedimentary Basins of Western Australia, Proceedings of PESA Symposium, Perth, pp. 42–62.
Brace, W. F. and Kohlstedt, D. L.: 1980, Limits on lithospheric stress imposed by laboratory experiments, J. Geophys. Res. 85:(B11), 6248–6252.
Braun, J. and Beaumont, C.: 1989, A physical explanation of the relationship between flank uplifts and the breakup unconformity at rifted continental margins, Geology 17: 760–764.
Byerlee, J. D.: 1978, Friction of rocks, Pure Appl. Geophys. 116: 615–626.
Carter, N. L. and Tsenn, M. C.: 1987, Flow properties of continental lithosphere, Tectonophysics 136: 27–63.
Chapman, D. S.: 1986, Thermal gradients in the continental crust, in J. B. Dawson, D. A. Carswell, J. Hall and K. H. Wedepohl (eds.), The Nature of the Lower Continental Crust, Geol. Soc. London Special Publ. 24: 63–70.
Clemens, J. D. and Vielzeuf, D.: 1987, Constraints on melting and magma production in the crust, Earth Planetary Sci. Lett. 86: 287–306.
Colwell, J. B., Symonds, P. A. and Crawford, A. J.: 1994, The nature of the Wallaby (Cuvier) Plateau and other igneous provinces of the west Australian margin, AGSO J. Australian Geol. Geophys. 15: 137–156.
Coward, M. P., Dewey, J. F. and Hancock, P. L.: 1987, Continental Extensional Tectonics, Geol. Soc. London Special Publ. 28: 619 pp.
Driscoll, N. W. and Karner, G. D.: 1998, Lower crustal extension across the Northern Carnarvon basin, Australia: Evidence for an eastward dip** detachment, J. Geophys. Res. 103: 4975–4991.
Drummond, B. J.: 1981, Crustal structure of the Precambrian terrains of northwest Australia from seismic refraction data, BMR J. Australian Geol. Geophys. 6: 123–135.
Drummond, B. J.: 1983, Detailed seismic velocity/depth models for the upper lithosphere of the Pilbara Craton, northwest Australia, BMR J. Australian Geol. Geophys. 8: 35–51.
Duncan, R. A and Richards, M. A.: 1991, Hotspots, mantle plumes, flood basalts, and true polar wander, Rev. Geophys. 29: 31–50.
Eldholm, O, Skogseid, J., Planke, S. and Gladczenko, T. P.: 1995, Volcanic margin concepts, in E. Banda, M. Torne and M. Talwani (eds.), Rifted Ocean-Continent Boundaries, pp. 1–16.
Exon, N. F.: 1994, An introduction to the geology of the outer margin of Australia's North West Shelf, AGSO J. Australian Geol. Geophys. 15: 3–10.
Exon, N. F. and Buffler, R. T.: 1992, Mesozoic seismic stratigraphy and tectonic evolution of the western Exmouth Plateau, in U. von Rad, B. U. Haq et al. (eds), Proceeding of the Ocean Drilling Program Vol. 122, College Station, Texas, Ocean Drilling Program, pp. 61–81.
Exon, N. F. and Colwell, J.B.: 1994, Geological history of the outer North West Shelf of Australia: a synthesis, AGSO J. Australian Geol. Geophys. 15: 177–190.
Fountain, D. M. and Christensen, N. I.: 1989, Composition of the continental crust and upper mantle: a review, Memoir-Geol. Soc. Am. 72: 711–742.
Frey, Ø.: 1998, Deep crustal structure, Rheology, and evolution of the Gascoyne Volcanic Margin, Western Australia, Cand. Scient. thesis, University of Oslo, 114 pp.
Fullerton, L. G., Sager, W. W. and Handschumacher, D. W.: 1989, Late Jurassic-Early Cretaceous evolution of the eastern Indian Ocean adjacent to northwest Australia, J. Geophys. Research 94: 2937–2953.
Goetze, C. and Evans, B.: 1979, Stress and temperature in the bending lithosphere as constrained by experimental rock mechanics, Geophys. J. Roy. Astron. Soc., 59: 463–478.
Gradstein, F. M. and von Rad, U.: 1991, Stratigraphic evolution of Mesozoic continental margin and oceanic sequences: Northwest Australia and northern Himalayas, in A. W. Meyer, T. A. Davies and S. W Wise (eds), Evolution of Mesozoic and Cenozoic Continental Margins, Marine Geology 102: 131–173.
Hopper, J. R., Mutter, J. C., Larson, R. L, Mutter, C. Z. and Northwest Australia Study Group: 1992, Magmatism and rift margin evolution: Evidence from northwest Australia, Geology 20: 853–857.
Howell, E. A.: 1988, The Harriet oilfield, in P. G. Purcell and R. R. Purcell (eds), The Northwest Shelf, Australia, Proceedings of PESA Symposium, Perth, pp. 391–401.
Kirby, S. H.: 1983, Rheolohy of the lithosphere, Rev. Geophys. Space Phys. 21: 1458–1487.
Kopsen, E. and McGann, G.: 1985, A review of the hydrocarbon habitat of the western and central Barrow-Dampier Sub-Basin, Western Australia, The APEA J. 25: 154–176. Lorenzo, J. M, Mutter, J, C, Larson, R. L. and Northwest Australia Study Group: 1991, Development of the continent-ocean transform boundary of the southern Exmouth Plateau, Geology 19: 843–846.
Malmcolm, R. J., Pott, B. C. and Delfos, E.: 1991, A new tectonostratigraphic synthesis of the North West Cape area, The APEA J. 31: 154–176.
McKenzie, D. and Bickle, M. J.: 1988, The volume and composition of melt generated by extension of the lithosphere, J. Petrology 29: 625–679.
Mihut, D. and Müller, R. D.: 1998, Volcanic margin formation and Mesozoic rift propagators in the Cuvier abyssal plain off Western Australia, J. Geophys. Res., 103: 27135–27150.
Müller, R.D., Mihut, D. and Baldwin, S.: 1998, A new kinematic model for the formation and evolution of the Northwest and West Australian margin, in P. G. Purcell and R. R. Purcell (eds), The Sedimentary Basins of Western Australia 2, pp. 55–72.
Mitchum, R. M. Jr., Vail, P. R. and Sangree, J.B.: 1977, Seismic stratigraphy and global changes of sea level, Part 6: Stratigraphic interpretation of seismic reflection patterns in depositional sequences, Memoir-Am. Assoc. Petroleum Geol. 26: 117–133.
Mutter, J. C., Buck, W. R. and Zehnder, C. M.: 1988, Convective partial melting: 1. A model for the formation of thick basaltic sequences during initiation of spreading, J. Geophys. Res. 93: 1031–1048.
Mutter, J. C. and 10 others: 1989, Extension of the Exmouth Plateau, offshore northwestern Australia: Deep seismic reflection/refraction evidence for simple and pure shear mechanisms, Geology 17: 15–18.
Ord, A. and Hobbs, B. E.: 1989, The strength of continental crust, detachment zones and the development of plastic instabilities, Tectonophysics 158: 269–289.
Pedersen, T, Heeremans, M., van der Beek, P.: 1998, Models of crustal anatexis in volcanic rifts: applications to southern Finland and the Oslo Graben, southeast Norway, Geophys. J. Int. 132: 239–255.
Planke, S., Symonds, P. A., Alvestad, E. and Skogseid, J.: 1999, Seismic volcanostratigraphy of large-volume basaltic extrusives on rifted margins, J. Geophys. Res., in press.
Planke, S., Alvestad, E. and Eldholm, O.: 1999, Seismic characteristics of basaltic extrusive and intrusive rocks, The Leading Edge 18: 342–348.
Planke, S., Symonds, P. A. and Müller, D.: 1996, Formation of Volcanic Rifted Margins and Oceanic Plateaus: Mantle plumes Versus Non-Mantle Plume Hypothesis on the Western Australia Volcanic Margin (Abstract), AGU Fall Meeting.
Planke, S., Symonds, P. A., Müller, D, Crawford, A. J., Mihut, D., Hopper, J. R., Colwell, J. B. and Coffin, M. F.: 1997, Formation of a Volcanic Rifted Margin in a Non-Mantle Plume Environment — A Proposal Drill the Cuvier Volcanic Margin off Western Australia.
Pollack, H. N. and Chapman, D. S.: 1977, On the regional variation of heat flow, geotherms and lithospheric thickness, Tectonophysics 38: 279–296.
Raia, F. and Spera, F. J.: 1997, Simulations of crustal anatexis: Implications for the growth and differentiation of continental crust, J. Geophys. Res. 102: 22629–22648.
Ranalli, G.: 1995, Rheology of the Earth, Chapman & Hall, London, 413 pp.
Rudnick, R. L. and Fountain, D. M.: 1995, Nature and composition of the continental crust: a lower crust perspective, Rev. Geophys. 33: 267–309.
Stagg, H. M. J. and Colwell, J. B.: 1994, The structural foundation of the Northern Carnarvon Basin, in P. G. Purcell and R. R. Purcell (eds), The Sedimentary Basins of West Australia, pp. 349–364.
Symonds, P. A., Planke, S., Frey, Ø. and Skogseid, J.: 1998, Volcanic evolution of the Western Australian continental margin and its implications for basin development, in P. G. Purcell and R. R. Purcell (eds), The Sedimenetary Basins of Western Australia 2: Proce. Petrol. Expl.Soc. Australia Symposium, Perth 1998, pp. 33–54.
Thompson, R. N. and Gibson, S. A.: 1991, Subcontinental mantle plumes, hotspots and pre-existing thinspots, Geol. Soc. London J. 148: 973–977.
Wells, P. R. A.: 1980, Thermal models for the magmatic accretion and subsequent metamorphism of continental crust, Earth Planet. Sci. Lett. 46: 253–265.
White, R. S. and McKenzie, D.: 1989, Magmatism at rift zones: the generation of volcanic continental margins and flood basalts, J. Geophys. Res. 94: 7685–7729.
Williamson, P. E., Swift, M. G., Kravis, S. P., Falvey, D. A. and Brassil, F.: 1990, Permo-carboniferous rifting of the Exmouth Plateau region (Australia): An intermediate plate model, in B. Pinet and C. Bois (eds), The Potential of Deep Seismic Profiling for Hydrocarbon Exploration, Editions Technip, Paris, pp. 135–248.
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Frey, Ø., Planke, S., Symonds, P.A. et al. Deep crustal structure and rheology of the Gascoyne volcanic margin, western Australia. Marine Geophysical Researches 20, 293–311 (1998). https://doi.org/10.1023/A:1004791330763
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DOI: https://doi.org/10.1023/A:1004791330763