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Cryogenian Glaciation and the Onset of Carbon-Isotope Decoupling” by N

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Cryogenian Glaciation and the Onset of Carbon-Isotope Decoupling” by N CORRECTED 21 MAY 2010; SEE LAST PAGE REPORTS 13. J. Helbert, A. Maturilli, N. Mueller, in Venus Eds. (U.S. Geological Society Open-File Report 2005- M. F. Coffin, Eds. (Monograph 100, American Geophysical Geochemistry: Progress, Prospects, and New Missions 1271, Abstracts of the Annual Meeting of Planetary Union, Washington, DC, 1997), pp. 1–28. (Lunar and Planetary Institute, Houston, TX, 2009), abstr. Geologic Mappers, Washington, DC, 2005), pp. 20–21. 44. M. A. Bullock, D. H. Grinspoon, Icarus 150, 19 (2001). 2010. 25. E. R. Stofan, S. E. Smrekar, J. Helbert, P. Martin, 45. R. G. Strom, G. G. Schaber, D. D. Dawson, J. Geophys. 14. J. Helbert, A. Maturilli, Earth Planet. Sci. Lett. 285, 347 N. Mueller, Lunar Planet. Sci. XXXIX, abstr. 1033 Res. 99, 10,899 (1994). (2009). (2009). 46. K. M. Roberts, J. E. Guest, J. W. Head, M. G. Lancaster, 15. Coronae are circular volcano-tectonic features that are 26. B. D. Campbell et al., J. Geophys. Res. 97, 16,249 J. Geophys. Res. 97, 15,991 (1992). unique to Venus and have an average diameter of (1992). 47. C. R. K. Kilburn, in Encyclopedia of Volcanoes, ~250 km (5). They are defined by their circular and often 27. R. J. Phillips, N. R. Izenberg, Geophys. Res. Lett. 22, 1617 H. Sigurdsson, Ed. (Academic Press, San Diego, CA, radial fractures and always produce some form of volcanism. (1995). 2000), pp. 291–306. 16. G. E. McGill, S. J. Steenstrup, C. Barton, P. G. Ford, 28. C. M. Pieters et al., Science 234, 1379 (1986). 48. We have rounded these numbers in recognition that the Geophys. Res. Lett. 8, 737 (1981). 29. B. Fegley Jr., R. G. Prinn, Nature 337, 55 (1989). age estimates have higher uncertainties than the volume 17. R. J. Phillips, M. C. Malin, Annu. Rev. Earth Planet. Sci. 30. A. H. Treiman, C. C. Allen, Lunar Planet. Sci. Conf. XXV, estimates. 12, 411 (1984). 1415 (1994). 49. G. Choblet, E. M. Parmentier, Phys. Earth Planet. Inter. 18. E. R. Stofan, S. E. Smrekar, D. L. Bindschadler, D. Senske, 31. M. I. Zolotov, V. P. Volkov, in Venus Geology, 173, 290 (2009). J. Geophys. Res. 23, 317 (1995). Geochemistry, Geophysics—Research Results from the 50. M. E. Davies et al., Celestial Mech. 39, 103 (1986). 19. Estimated elastic thickness values at Themis Regio are USSR (Univ. of Arizona Press, Tucson, AZ, 1992), 51. P. K. Seidelmann et al., Celestial Mech. Dyn. Astron. 82, typically 10 to 20 km (20, 21). The authors of (22) pp. 177–199. 83 (2002). conducted a global admittance study and found values of 32. B. Fegley, A. H. Treiman, V. L. Sharpton, Proc. Lunar 52. M. E. Davies et al., J. Geophys. Res. 97, 13,141 elastic thickness of 0 to 50 km at both Dione and Planet. Sci. 22, 3 (1992). (1992). Themis Regiones. Their analysis also shows regions of 33. B. Fegley, K. Lodders, A. H. Treiman, G. Klingelhöfer, 53. A. S. Konopliv, W. S. Banerdt, W. L. Sjogren, Icarus 139, large elastic thickness, up to 100 km, in the northern Icarus 115, 159 (1995a). 3 (1999). portion of Dione Regio covering Ushas Mons. Estimates of 34. B. Fegley et al., Icarus 118, 373 (1995b). 54. G. L. Hashimoto, T. Imamura, Icarus 154, 239 (2001). average apparent depth of compensation (ADC) for Dione 35. A. M. Baldridge, S. J. Hook, C. I. Grove, G. Rivera, 55. This research was carried out in part at the Jet Propulsion and Themis Regiones are 130 km and 100 km (21), Remote Sens. Environ. 113, 711 (2009). Laboratory, California Institute of Technology, and was Downloaded from respectively. The elastic thickness at Imdr Regio cannot 36. L. T. Elkins-Tanton et al., Contrib. Minerol. Petrol. 153, sponsored by the Planetary Geology and Geophysics be reliably estimated due to the low resolution of the 191 (2007). Program and NASA. We gratefully acknowledge the work gravity field in that region (53). Stofan et al.(18) 37. S. A. Gibson, R. N. Thompson, A. P. Dickin, Earth Planet. of the entire Venus Express and VIRTIS teams. We thank estimated an ADC of 260 km, which is consistent with a Sci. Lett. 174, 355 (2000). the European Space Agency, Agenzia Spaziale Italiana, deep plume. 38. L. S. Glaze, J. Geophys. Res. 104, 18,899 (1999). Centre National des Etudes Spatiales, CNRS/Institut 20. M. Simons, S. C. Solomon, B. H. Hager, Geophys. J. Int. 39. New Scientist 23, 52 (2009) (www.newscientist.com/ National des Sciences de l’Univers, and the other 13, 24 (1997). article/dn17534). national space agencies that have supported this 21. S. E. Smrekar, E. R. Stofan, Icarus 139, 100 (1999). 40. V. S. Meadows, D. Crisp, J. Geophys. Res. 101, 4595 research. VIRTIS is led by INAF-IASF, Rome, Italy, and http://science.sciencemag.org/ 22. F. S. Anderson, S. E. Smrekar, J. Geophys. Res. Planets (1996). LESIA, Observatoire de Paris, France. 111, E08006 (2006). 41. B. Fegley, Icarus 128, 474 (1997). 23. S. T. Keddie, J. W. Head, J. Geophys. Res. 101, 11,729 42. E. R. Stofan, A. W. Brian, J. E. Guest, Icarus 173, 312 7 January 2010; accepted 25 March 2010 (1995). (2005). Published online 8 April 2010; 24. E. R. Stofan, J. E. Guest, A. W. Brian, Mapping of V-28 43. P. R. Hooper, in Large Igneous Provinces: Continental, 10.1126/science.1186785 and V-53, T. K. P. Gregg, K. L. Tanaka, R. S. Saunders, Oceanic and Planetary Flood Volcanism, J. J. Mahoney, Include this information when citing this paper. whelms the signal from primary biomass frac- Cryogenian Glaciation and the Onset tionated from contemporaneous DIC (4). We consider the large oceanic reservoir model and, on September 9, 2019 of Carbon-Isotope Decoupling as in (2), use the term DOC to collectively refer to organic carbon that is truly dissolved as well as suspended colloidal organic carbon and fine Nicholas L. Swanson-Hysell,1 Catherine V. Rose,1 Claire C. Calmet,1 Galen P. Halverson,2* POC. The buildup and maintenance of a large Matthew T. Hurtgen,3 Adam C. Maloof1† DOC pool implies low Corg remineralization— perhaps associated with low oxygen and sulfate Global carbon cycle perturbations throughout Earth history are frequently linked to changing levels—but high nutrient liberation efficiency. paleogeography, glaciation, ocean oxygenation, and biological innovation. A pronounced In such an ocean, the d13CoftheDICpoolis carbonate carbon-isotope excursion during the Ediacaran Period (635 to 542 million years sensitive to inputs (via remineralization) from the ago), accompanied by invariant or decoupled organic carbon-isotope values, has been explained 13C-depleted DOC pool that can drive negative with a model that relies on a large oceanic reservoir of organic carbon. We present carbonate and excursions. The end of the invariance in the organic matter carbon-isotope data that demonstrate no decoupling from approximately 820 to 13 d Corg record in the latter stages of the Shuram- 760 million years ago and complete decoupling between the Sturtian and Marinoan glacial Wonoka anomaly has been interpreted as the events of the Cryogenian Period (approximately 720 to 635 million years ago). Growth of the demise of the large DOC pool (2, 3). organic carbon pool may be related to iron-rich and sulfate-poor deep-ocean conditions facilitated Stratigraphically constrained coupled records by an increase in the Fe:S ratio of the riverine flux after Sturtian glacial removal of a long-lived 13 13 of d Ccarb–d Corg at sufficient detail to test this continental regolith. carbon cycle model have been available only from carbonates of Ediacaran age (2, 3). We 13 13 13 13 hroughout most of the Phanerozoic Eon variant d Corg during large changes to d Ccarb present paired d Ccarb and d Corg data from [542 million years ago (Ma) to present], across the ~580 million-year-old Shuram-Wonoka d13 paired records of carbonate carbon ( Ccarb) anomaly (Fig. 1 and fig. S1). This behavior has 1 T 13 Department of Geosciences, Princeton University, Princeton, d and coeval bulk organic carbon ( Corg) iso- been used to develop and support a model for NJ 08544, USA. 2Geology and Geophysics, University of Ade- topes are consistent with a model in which the the Neoproterozoic (1000 to 542 Ma) carbon laide Mawson Laboratories, Adelaide, SA 5005, Australia. 13 3 organic carbon in marine sediments is derived cycle in which invariant d Corg values result from Department of Earth and Planetary Sciences, Northwestern and fractionated from contemporaneous dissolved a very large oceanic reservoir of 13C-depleted dis- University, Evanston, IL 60208, USA. d13 *Present address: Department of Earth and Planetary Sci- inorganic carbon (DIC). In contrast, Ccarb and solved organic carbon (DOC) and particulate ences, McGill University, Montreal, Quebec H3A 2A7, Canada. d13 Corg records from Ediacaran (635 to 542 Ma) organic carbon (POC) (or, alternatively, sourced †To whom correspondence should be addressed. E-mail: carbonate successions (1–3) show relatively in- from a large sedimentary reservoir) that over- [email protected] 608 30 APRIL 2010 VOL 328 SCIENCE www.sciencemag.org REPORTS Fig. 1. Carbonate carbon iso- older Neoproterozoic strata: the Bitter Springs ~551 Ma Fm. tope values and organic carbon POUND Formation of the Amadeus Basin, central Aus- 700 isotope values from Neoprotero- tralia, that was deposited during the Tonian Pe- zoic carbonates of Australia with 600 riod (1000 to ~720 Ma) and the Etina-Trezona simplified lithostratigraphy. The Formations of the adjacent Adelaide Rift Com- plotted lithofacies represent the 500 plex deposited during the Cryogenian Period lithologies that dominate each (~720 to 635 Ma) (5). Together with published interval, with wider boxes corre- 400 data from the Ediacaran Wonoka Formation (1), sponding to deposition in shal- also of the Adelaide Rift Complex, these records lower water.
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