Bedout: A possible end-Permian impact crater offshore of northwestern Australia

Science

Volumn 304, Issue 5676, 2004, Pages 1469-1476

  Becker, L ^a   Poreda, R J ^b   Basu, A R ^b   Pope, K O ^c   Harrison, T M ^d   Nicholson, C ^a   Iasky, R ^e  

^a UNIVERSITY OF CALIFORNIA   (United States)

^b UNIVERSITY OF ROCHESTER   (United States)

^c Geo Eco Arc Research   (United States)

^d AUSTRALIAN NATIONAL UNIVERSITY   (Australia)

^e GEOLOGICAL SURVEY OF WESTERN AUSTRALIA   (Australia)

Author keywords

[No Author keywords available]

Indexed keywords

ARGON; BOUNDARY CONDITIONS; FUSED SILICA; GRAVITATION; IMAGE ANALYSIS; ROCKS; SEDIMENTS; SEISMOLOGY;

BEDOUTS; END-PERMIAN IMPACT; MELT ROCKS; NORTHWESTERN AUSTRALIA;

OFFSHORE STRUCTURES;

GLASS; MINERAL; SILICON DIOXIDE;

BRECCIA; GRAVITY SURVEY; IMPACT STRUCTURE; IMPACTITE; PERMIAN; SEISMIC SURVEY;

ARTICLE; AUSTRALIA; GEOLOGICAL TIME; GRAVITY; IMAGE ANALYSIS; MELTING POINT; PERMIAN; PRIORITY JOURNAL; ROCK; SEDIMENT; SEDIMENTOLOGY; STONE ANALYSIS;

ARGON; AUSTRALIA; CRYSTALLIZATION; GEOGRAPHY; GEOLOGIC SEDIMENTS; GLASS; METEOROIDS; MINERALS; RADIOISOTOPES; SILICON DIOXIDE;

AUSTRALASIA; AUSTRALIA;

EID: 2642513134     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1093925     Document Type: Article

References (53)

1. L. Becker et al., Science 291, 1530 (2001).
2. L. Becker, R. J. Poreda, T. E. Bunch, Proc. Natl. Acad. Sci. U.S.A. 97, 2979 (2000).
3. L. Becker, C. Nicholson, R. J. Poreda, American Geophysical Union (AGU) Abstract, December 12 to 17 2002, OS22C-0291 (2002).
4. G. J. Retallack et al., Geology 26, 979 (1998).
5. K. Kaiho et al., Geology 29, 815 (2001).
6. S. Miono, Y. Nakayama, K. Hanamoto, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interactions Mater. Atoms 150, 516 (1999).
7. R. J. Poreda, L. Becker, Astrobiology 3, 120 (2003).
8. A. R. Basu, M. I. Petaev, R. J. Poreda, S. B. Jacobsen, L. Becker, Science 302, 1388 (2003).
9. Similar metal grains are found in the boundary layer (at the base of bed 25) at Meishan, China (5). The common occurrence of Fe-Ni-Si grains at the Graphite Peak, Antarctica, and Meishan, China, P-T boundary layers is evidence for their apparent relationship as pointed out in (8). These "event-marker" magnetic grains occur only in the boundary layer and are absent in samples above and below, both at Meishan and Graphite Peak. The unique chemical composition of the metal-rich grains (for example, condensates) suggests formation in the vapor cloud as a result of the impact event (8).
10. S. Miono, C. Z. Zheng, Y. Nakayama, Nucl. Instrum. Methods Phys. Res. Sect. B Beam Interactions Mater. Atoms 109, 612 (1996).
11. L. Alvarez, W. Alvarez, F. Asaro, H. Michel, Science 208, 1095 (1980).
12. A. R. Hildebrand et al., Geology 19, 867 (1991).
13. J. Gorter, Pet. Explor. Soc. Aust. News 1996, 33 (1996).
14. J. Gorter, Aust. Pet. Prod. Explor. Assoc. J. 1998, 159. (1998).
15. The JNOC data range from very poor to moderate in quality. Most sections are adversely affected by seafloor multiples due to shallow water depth. These lines are now being reprocessed by Seismic Australia to improve the quality of the data and will be incorporated in future studies.
16. S. A. Smith, thesis, University of Adelaide, Adelaide, Australia (1999).
17. P. G. Purcell, R. R. Purcell, in The Sedimentary Basins of Western Australia, P. G. Purcell, R. R. Purcell, Eds. [Proceedings of the Petroleum Exploration Society of Australia (PESA) Symposium, PESA, Perth, Australia, 1994], pp. 769-777.
18. AGSO NW Shelf Study Group, in The Sedimentary Basins of Western Australia, P. G. Purcell, R. R. Purcell, Eds. (Proceedings of the PESA, Symposium, PESA, Perth, Australia, 1994), pp. 63-76.
19. S. Colwell, B. Stagg, in The Sedimentary Basins of Western Australia, Purcell, P. G. Purcell, R. R. Purcell, Eds. (Proceedings of the PESA, Symposium, PESA, Perth, Australia, 1994), pp. 757-768.
20. Well reports, La Grange-1 and Bedout-1 exploration wells [Geological Survey of Western Australia (GSWA), Perth, Australia, 1971 and 1983].
21. T. R. Charlton, J. Asian Earth Sci. 19, 595 (2001).
22. B. C. Schuraytz, V. L. Sharpton, L. E. Marin, Geology 22, 868 (1994).
23. V. L. Sharpton et al., Nature 359, 819 (1992).
24. P. Claeys, S. Heuschkel, E. Lounejeva-Baturina, G. Sanchez-Rubio, D. Stoffler, Meteorit. Planet. Sci. 38, 1299 (2003).
25. The Bedout-1 impact melt breccia is similar to the Yucatan-6 (Fig. 4) melt breccia, with centimeter-sized clasts of fine-grained to glassy, typically altered, melt rock in a fine- to medium-grained melt rock matrix composed mainly of feldspars, chlorite, and carbonate. If the Bedout impact melt breccia reflects the compositions of the target rocks, then one can assume that the upper part of the Bedout basement was dominated by more feldspar-rich rocks or basaltic volcanics (24). The difference between the Bedout-1 and Yucatan-6 impact melt breccias is that most of the clasts and the matrix in Bedout have been pervasively altered to chlorite.
26. The fossil ooid fragments and carbonate clast lack shock features but are intimately associated with the glassy (silicate) matrix, which is consistent with an impact origin. Similar observations have been made for the Haughton, Ries, and Chicxulub crater breccias. These textural features may be attributed to carbonate-silicate liquid immiscibility (27). The recognition of fossil ooids in the end-Permian-aged Bedout-1 impact melt breccia suggests that sedimentary (marine) target rocks were also present at the time of impact.
27. G. Graup, Meteorit. Planet. Sci. 34, 425 (1999).
28. B. M. French, Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures (LPI Contribution No. 594, Lunar Planetary Institute, Houston, TX, 1998).
29. 39Ar)K = 8.0. Blanks and backgrounds were generally atmospheric and/or insignificant in terms of fraction of gas analyzed. Air standards were used to determine mass fractionation, which is known within about 0.3% and was assumed not to vary on the time scale of sample analysis.
30. Sample cuttings from the Lagrange-1 well (latitude 18°16′ 37.4″S, longitude 119°18′0.7.2″E) were provided by the British Petroleum Company (BP) to A. Webb of Amdel Petrology, Australia. The results were published in the BP company report (20) and are currently available upon request from Geoscience Australia in Canberra or the GSWA. K/Ar dating was performed on plagioclases handpicked by Webb from cuttings sampled in the lowest (10,215 feet) section of the Lagrange-1 exploration well. This sample was described as suitable for age dating, resulting in an age of 253 ± 5 My.
31. S. A. Reechmann, A. J. Mebersen, in P. G. Purcell, Ed., The Canning Basin, Western Australia [Proceedings of the Geological Society of Australia/PESA (GSA/PESA) Canning Basin Symposium, PESA, Perth, Australia, 1984], pp. 389-400.
32. A. Kritski, thesis, University of Sydney, Sydney, Australia (2000).
33. G. L. Christeson, Y. Nakamura, R. T. Buffler, J. Morgan, M. Warner, J. Geophys. Res. 106, 751 (2001).
34. J. Melosh, Nature 414, 861 (2001).
35. Like Chicxulub, the refraction data show that the Moho is distorted beneath the Bedout High (33, 34). The rise of the Moho, however, is slightly offset from the central peak, suggesting that the material beneath the transient crater (∼20 km of crust) was not just simply pushed down under the crater floor as observed for Chicxulub (34). The deeper crustal structure of Bedout is less well resolved (32); thus, its relation to the Bedout High and subsequent continental rifting needs further investigation.
36. E. L. Horstman, in The Canning Basin, Western Australia, P. G. Purcell, Ed. (Proceedings of the GSA/PESA Canning Basin Symposium, PESA, Perth, Australia, 1984), pp. 240-267.
37. J. Morgan, M. Warner, Geology 27, 407 (1999).
38. F. Tsikalas, S. T. Gudlaugsson, J. I. Faleide, J. Geophys. Res. 103; 30, 430 (1998).
39. F. Tsikalas, S. T. Gudlaugsson, J. I. Faleide, Geol. Soc. Am. Bull. 110, 537 (1998).
40. G. A. Izett, Geol. Soc. Am. Spec. Pap. 249, 100 (1990).
41. J. Smit, Annu. Rev. Earth Planet. Sci. 27, 75 (1999).
42. K. O. Pope, Geology 30, 99 (2002).
43. H. I. Petaev, S. B. Jacobsen, A. R. Basu, L. Becker, Lunar Planet. Sci. Conf. Abstr. XXXV, 1216 (2004).
44. F. T. Kyte J. A. Bostwick, Earth Planet. Sci. Lett. 132, 113 (1995).
45. D. Stöffler, Fortschr. Mineral. 49, 50 (1972).
46. M. K. Riechow et al., Science 296, 1846 (2002).
47. A. P. Jones et al., Earth Planet. Sci. Lett. 6343, 1 (2002).
48. A. Glikson, Geology 27, 387 (1999).
49. H. J. Melosh, Catastrophic Events and Mass Extinction: Impacts and Beyond Conference Abstract 3144 (2000).
50. B. A. Ivanov, H. J. Melosh, Lunar Planet. Sci. Conf. Abstr. XXXIV, 1338 (2003).
51. P. R. Renne, A. R. Basu, Science 253, 176 (1991).
52. A. R. Basu et al., Science 261, 902 (1993).
53. Supported by NASA grants in Exobiology and by an NSF Continental Dynamics Workshop sponsored by L. Johnson. We thank P. Cronin and E. Resiak for assistance with the Bedout-1 and Lagrange-1 core sampling and A. Fleming for access to the AGSO regional seismic survey. We also thank the GSWA in Perth for hosting the NSF workshop and R. Emms and A. Mory for assistance with additional core sampling and access to well reports. Special thanks go to J. Hunt for assistance with the microprobe; AINSIE and ANSTO for the neutron irradiation of the Bedout core material and funding; A. Lockwood for the Bedout High gravity model; J. Dunlap for assistance with the argon dating; F. Tsikalas for use of the Mjølnir figure; A. Kritski and S. Smith for access to their thesis data; and G. Retallack, A. Glikson, J. Gorter, and the Bedout Working Group for many helpful discussions and suggestions.