Isotopic evidence for the cretaceous-tertiary impactor and its type

Science

Volumn 282, Issue 5390, 1998, Pages 927-929

  Shukolyukov, A ^a   Lugmair, G W ^a,b  

^a UNIVERSITY OF CALIFORNIA   (United States)

^b MAX PLANCK INSTITUTE FOR CHEMISTRY   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

CHROMIUM;

CHROMIUM; CRETACEOUS-TERTIARY BOUNDARY; IMPACT; MASS EXTINCTION;

ARTICLE; ASTRONOMY; HYPOTHESIS; MASS SPECTROMETRY; PRIORITY JOURNAL; SEDIMENT;

CHROMIUM; CHROMIUM ISOTOPES; DENMARK; EARTH (PLANET); GEOLOGIC SEDIMENTS; MASS SPECTROMETRY; METEOROIDS; SPAIN;

EID: 0032582496     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.282.5390.927     Document Type: Article

References (35)

1. L. W. Alvarez, W. Alvarez, F. Asaro, H. V. Michel, Science 208, 1095 (1980); R. Ganapaty, ibid. 209, 921 (1980); J. Smit and J. Hertogen, Nature 285, 198 (1980).
2. L. W. Alvarez, W. Alvarez, F. Asaro, H. V. Michel, Science 208, 1095 (1980); R. Ganapaty, ibid. 209, 921 (1980); J. Smit and J. Hertogen, Nature 285, 198 (1980).
3. L. W. Alvarez, W. Alvarez, F. Asaro, H. V. Michel, Science 208, 1095 (1980); R. Ganapaty, ibid. 209, 921 (1980); J. Smit and J. Hertogen, Nature 285, 198 (1980).
4. F. T. Kyte, Z. Zhou, J. T. Wasson, Nature 288, 651 (1980).
5. D. A. Russell, Annu. Rev. Earth Planet Sci. 7, 163 (1979); J. Smit, Geol. Soc. Am. Spec. Pap. 190, 329 (1982); E. Buffetaut, Nature 310, 26 (1984).
6. D. A. Russell, Annu. Rev. Earth Planet Sci. 7, 163 (1979); J. Smit, Geol. Soc. Am. Spec. Pap. 190, 329 (1982); E. Buffetaut, Nature 310, 26 (1984).
7. D. A. Russell, Annu. Rev. Earth Planet Sci. 7, 163 (1979); J. Smit, Geol. Soc. Am. Spec. Pap. 190, 329 (1982); E. Buffetaut, Nature 310, 26 (1984).
8. C. B. Officer, A. Hallam, C. L. Drake, J. D. Devine, Nature 326, 143 (1987); A. Hallam, Science 238, 1237 (1987).
9. C. B. Officer, A. Hallam, C. L. Drake, J. D. Devine, Nature 326, 143 (1987); A. Hallam, Science 238, 1237 (1987).
10. A. R. Hildebrand et al., Geology 19, 867 (1991).
11. F. T. Kyte, J. A. Bostwick, L. Zhou, Geol. Soc. Am. Spec. Pap. 307, 389 (1996).
12. J. M. Luck and K. K. Turekian, Science 222, 613 (1983).
13. S. J. G. Galer, J. D. Macdougall, D. J. Erickson III, Geophys. Res. Lett. 16, 1302 (1989); A. Dia, G. Mannès, B. Dupré, C. J. Allègre, Chem. Geol. 75, 291 (1989).
14. S. J. G. Galer, J. D. Macdougall, D. J. Erickson III, Geophys. Res. Lett. 16, 1302 (1989); A. Dia, G. Mannès, B. Dupré, C. J. Allègre, Chem. Geol. 75, 291 (1989).
15. O. Eugster, J. Geiss, U. Krähenbühl, Earth Planet. Sci. Lett. 74, 27 (1985).
16. F. T. Kyte, J. Smit, J. T. Wasson, ibid. 73, 183 (1985).
17. G. W. Lugmair and A. Shukolyukov, Geochim. Cosmochim. Acta, in press.
18. J.-L. Birck and C. J. Allègre, Geophys. Res. Lett. 12, 745 (1985).
19. _, Nature 331, 579 (1988); I. D. Hutcheon, E. Olsen, J. Zipfel, G. J. Wasserburg, Lunar Planet. Sci. XXIII, 565 (1992); L. E. Nyquist et al., ibid., XXVIII, 1033 (1997).
20. _, Nature 331, 579 (1988); I. D. Hutcheon, E. Olsen, J. Zipfel, G. J. Wasserburg, Lunar Planet. Sci. XXIII, 565 (1992); L. E. Nyquist et al., ibid., XXVIII, 1033 (1997).
21. _, Nature 331, 579 (1988); I. D. Hutcheon, E. Olsen, J. Zipfel, G. J. Wasserburg, Lunar Planet. Sci. XXIII, 565 (1992); L. E. Nyquist et al., ibid., XXVIII, 1033 (1997).
22. S. R. Taylor and S. M. McLennan, The Continental Crust: Its Composition and Evolution (Blackwell, Oxford, 1985), pp. 57-72.
23. 2O-free Cl-chondrite contains 3.32 mg of Cr per gram [E. Anders and N. Grevesse, Geochim. Cosmochim. Acta 53, 197 (1989)]. Thus, the calculated cosmic Cr concentrations in the noncarbonate fractions of SK10, FC10, and SM503 are 339, 387, and 320 ppm, respectively, whereas the measured Cr concentrations in the noncarbonate fractions of these samples are 332, 255, and 1011 ppm, respectively. The calculated and measured Cr concentrations of SK10 and FC10 are comparable, which indicates the plausibility of high cosmic Cr concentrations in these samples. The measured Cr concentration in SM503 is three times higher than that calculated from the Ir concentration. Because the Cr isotope signature of SM503 is essentially the same as that of SK10 and FC10, this difference is unlikely to be due to the presence of an abundant terrestrial component in SM503. Instead, it most likely reflects Cr/Ir fractionation in SM503: A severe elemental fractionation relative to the chondritic abundances has been observed in all K-T samples, and the ETCs calculated from various siderophile elements vary by a factor of 3 (10).
24. 52Cr = 0.051859 [W. R. Shields, T. J. Murphy, E. J. Cantanzaro, E. L. Garner, J. Res. Nat. Bur. Stand. 70A, 193 (1966)] as an internal standard. The necessity for a second-order fractionation correction and the method applied were extensively discussed in (11) and will not be repeated here.
25. D. A. Papanastassiou, Astrophys. J. 308, L27 (1986); F. A. Podosek et al., Meteorit. Planet. Sci. 32, 617 (1997).
26. D. A. Papanastassiou, Astrophys. J. 308, L27 (1986); F. A. Podosek et al., Meteorit. Planet. Sci. 32, 617 (1997).
27. M. Rotaru, J.-L. Birck, C. J. Allègre, Lunar Planet. Sci. XXI, 1037 (1990).
28. This finding is in accord with recent results [B. C. Schuraytz et al., Science 271, 1573 (1996); B. C. Schuraytz et al., Lunar Planet. Sci. Conf. XXIX, 1935 (1998)] on the refractory metal grains from the Chicxulub crater debris. The authors suggest that these grains are relicts of the Chicxulub basin-forming impactor and that the impactor contained refractory inclusions, which are a common component of various carbonaceous chondrite materials.
29. This finding is in accord with recent results [B. C. Schuraytz et al., Science 271, 1573 (1996); B. C. Schuraytz et al., Lunar Planet. Sci. Conf. XXIX, 1935 (1998)] on the refractory metal grains from the Chicxulub crater debris. The authors suggest that these grains are relicts of the Chicxulub basin-forming impactor and that the impactor contained refractory inclusions, which are a common component of various carbonaceous chondrite materials.
30. D. E. Brownlee, R. S. Rajan, D. A. Tomandl, in Comets, Asteroids, Meteorites, A. H. Delsemme, Ed. (Univ. of Toledo Bookstore Press, Toledo, OH, 1977), pp. 137-141.
31. J. G. Hills, Astrophys. J. 86, 1730 (1981).
32. M. R. Rampino and R. B. Stothers, Nature 308, 709 (1984).
33. K. A. Farley, A. Montanari, E. M. Shoemaker, C. S. Shoemaker, Science 280, 1250 (1998).
34. F. T. Kyte, Nature, in press.
35. Supported by NASA grant 5-4145. We are very grateful to F. T. Kyte and J. Smit for the K-T samples. We also thank M. Kastner and J. D. Macdougall for the control samples and Ch. McIsaac for his help in the lab and useful suggestions. F. T. Kyte's continued advice and his stimulating enthusiasm are highly appreciated.