Molybdenum Isotope Evidence for Widespread Anoxia in Mid-Proterozoic Oceans

Science

Volumn 304, Issue 5667, 2004, Pages 87-90

  Arnold, G L ^a   Anbar, A D ^a   Barling, J ^a,c   Lyons, T W ^b  

^a UNIVERSITY OF ROCHESTER   (United States)

^b UNIVERSITY OF MISSOURI   (United States)

^c UNIVERSITY OF BRITISH COLUMBIA   (Canada)

Author keywords

[No Author keywords available]

Indexed keywords

ENVIRONMENTAL IMPACT; HYDROGEN SULFIDE; ISOTOPES;

OXYGENATION;

MOLYBDENUM;

ISOTOPE; MOLYBDENUM;

ANOXIA; DISSOLVED OXYGEN; MOLYBDENUM; PALEOATMOSPHERE; PALEOCEANOGRAPHY; PROTEROZOIC;

ANOXIA; ARTICLE; ATMOSPHERE; MARINE ENVIRONMENT; OCEAN ENVIRONMENT; OXYGENATION; PRIORITY JOURNAL; PROTEROZOIC; SEDIMENTOLOGY;

EID: 1842529302     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1091785     Document Type: Article

References (42)

1. A. H. Knoll, in Origin and Early Evolution of the Metazoa, J. H. Lipps, P. W. Signor, Eds. (Plenum, New York, 1992), p. 53.
2. A. D. Anbar, A. H. Knoll, Science 297, 1137 (2002).
3. D. J. Des Marais et al., Astrobiology 2, 153 (2002).
4. H. D. Holland, The Chemical Evolution of the Atmosphere and Oceans (Princeton Univ. Press, Princeton, NJ, 1984).
5. H. D. Holland, Geochem. News 100, 20 (1999).
6. J. Farquhar, H. Bao, M. H. Thiemens, Science 289, 756 (2000).
7. D. E. Canfield, A. Teske, Nature 382, 127 (1996).
8. D. E. Canfield, Nature 396, 450 (1998).
9. D. E. Canfield, R. Raiswell, Am. J. Sci. 299, 697 (1999).
10. A. A. Pavlov, M. T. Hurtgen, J. F. Kasting, M. A. Arthur, Geology 31, 87 (2003).
11. A. J. Kaufman, S. Xiao, Nature 425, 279 (2003).
12. Y. Shen, D. E. Canfield, A. H. Knoll, Am. J. Sci. 302, 81 (2002).
13. Y. Shen, A. H. Knoll, M. R. Walter, Nature 423, 632 (2003).
14. L. C. Kah, T. W. Lyons, J. T. Chesley, Precambrian Res. 111, 203 (2001).
15. S. R. Emerson, S. S. Huested, Mar. Chem. 34, 177 (1991).
16. B. E. Erickson, G. R. Helz, Geochim. Cosmochim. Acta 64, 1149 (2000).
17. Y. Zheng, R. F. Anderson, A. van Geen, J. Kuwabara, Geochim. Cosmochim. Acta 64, 4165 (2000).
18. J. L. Morford, S. Emerson, Geochim. Cosmochim. Acta 63, 1735 (1999).
19. K. K. Bertine, K. K. Turekian, Geochim. Cosmochim. Acta 37, 1415 (1973).
20. J. McManus, T. F. Nagler, C. Siebert, C. G. Wheat, D. E. Hammond, Geochem. Geophys. Geosyst, 3, 10.1029/ 2002GC000356 (2002).
21. standard -1) × 1000
22. J. Barling, G. L. Arnold, A. D. Anbar, Earth Planet. Sci. Lett. 193, 447 (2001).
23. C. Siebert, T. F. Nagler, F. von Blanckenburg, J. D. Kramers, Earth Planet. Sci. Lett. 211, 139 (2003).
24. Values reported in text are the mean ± 2 SD for all analyses of each sample grouping, unless otherwise noted.
25. Details of materials, methods, sample descriptions, and alternative hypotheses are available as supporting material on Science Online.
26. Molybdenite ores are assumed to consist of Mo extracted by hydrothermal processes from surrounding crustal rocks, and hence are a rough proxy for crustal Mo.
27. Siebert et al. (23) found no Mo isotope fractionation during mild acid leaching of Mo from granite and basalt. Therefore, it is reasonable to hypothesize that Mo released during crustal weathering is isotopically similar to Mo in granite, basalt, and molybdenite.
28. 97/95Mo in Mn oxide-associated Mo.
29. J. Barling, A. D. Anbar, Earth Planet. Sci. Lett. 217, 315 (2004).
30. G. R. Helz et al., Geochim. Cosmachim. Acta 60, 3631 (1996).
31. J. W. Murray, Z. Top, E. Ozsoy, Deep-Sea Res. 38, S663 (1991).
32. I. H. Crick, C. J. Boreham, A. C. Cook, T. G Powell, Am. Assoc. Petrol. Geol. Bull. 72, 1495 (1988).
33. T. H. Donnelly, M. J. Jackson, Sediment. Geol. 58, 145 (1988).
34. D. E. Canfield, T. W. Lyons, R. Raiswell, Am. J. Sci. 296, 818 (1996).
35. The use of basinal Mo concentrations to infer global ocean Mo concentrations is not straightforward, as evidenced by the nearly 10-fold difference in Mo concentrations between euxinic sediments in the Cariaco Basin and Black Sea. Local effects specific to the depositional setting presumably dominate. Hence, Mo concentrations in sediments cannot easily be used alone to draw inferences about global ocean redox conditions.
36. eux = 0.54.
37. eux of the mid-Proterozoic samples ranges from 0.31 to 0.67%o; correspondingly, the euxinic sink could range from 82 to 62%.
38. A. D. Anbar, in Geochemistry of Non-Traditional Isotopes, C. Johnson, B. Beard, F. Albarede, Eds. (Mineralogical Society of America, Washington, DC, 2004), pp. 429-454.
39. eux is simplistic, but useful for schematic purposes.
40. eux can be compensated by a change in the areal extent of suboxic seafloor, whereas the Mo mass balance model assumes that suboxic sediments are a negligible sink for Mo.
41. H. D. Klemme, G. F. Ulmishek, Am. Assoc. Petrol. Geol. Bull. 75, 1809 (1991).
42. We thank Y. Shen, J. Brocks, A. H. Knoll, and H. D. Holland for providing samples of Proterozoic black shales, and G. Ravizza for Black Sea samples. F. Ramos, G. Williams, and S. Weyer assisted with sample analysis. Supported by NSF (EAR 0106712 and 0230183) and NASA (Exobiology program and the Astrobiology Institute).