『Abstract
　A model for the combined long-term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the GEOCARB III model [Berner R.A., Kothavala Z., 2001. GEOCARB III: a revised model of atmospheric CO2 over Phanerozoic time. Am. J. Sci. 301, 182-204] for CO2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for O2 [Berner R.A., 2001. Modeling atmospheric O2 over Phanerozoic time. Geochim. Cosmochim. Acta 65, 685-694]. New isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models. Sensitivity analysis is done by determining (1) the effect on weathering rates of using rapid recycling (rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks); (2) the effect on O2 of using different initial starting conditions; (3) the effect on O2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic δ¹³C for the past 200 million years; (4) the effect on sulfur isotope fractionation and on O2 of varying the size of O2 feedback during sedimentary pyrite formation; (5) the effect on O2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion, and the degree of exposure of coastal lands by sea level change; (6) the effect on CO2 of adding the variability of volcanic rock weathering over time [Berner, R.A., 2006. Inclusion of the weathering of volcanic rocks in the GEOCARBSULF model. Am. J. Sci. 306 (in press)]. Results show a similar trend of atmospheric CO2 over the Phanerozoic to the results of GEOCARB III, but with some differences during the early Paleozoic and, for variable volcanic rock weathering, lower CO2 values during the Mesozoic. Atmospheric oxygen shows a major broad late Paleozoic peak with a maximum value of about 30％ O2 in the Permian, a secondary less-broad peak centered near the Silurian/Devonian boundary, variation between 15％ and 20％ O2 during the Cambrian and Ordovician, a very sharp drop from 30％ to 15％ O2 at the Permo-Triassic boundary, and a more-or less continuous rise in O2 from the late Triassic to the present.』

1. Introduction
2. GEOCARBSULF modeling
　2.1. Fundamentals
　2.2. Rapid recycling and O2
　2.3. Initial values and O2
　2.4. Carbon isotope fractionation and O2
　2.5. Sulfur isotope fractionation and O2
　2.6. Land area, relief, erosion and O2
　2.7. Atmospheric carbon dioxide
3. discussion and conclusions
Acknowledgements
References

Fig. 19. Plot of O2 vs time from Bergman et al. (2004). Fig. 20. Plot of O2 vs time for the standard GEOCARBSULF model with a crude estimate of the range of error based on sensitivity study. Triassic O2 values differ from those shown in the other plots of the present study because of the use of alternative δ13C data (Korte et al., 2005a and Korte et al., 2005b; see Fig. 1). This enables O2 concentrations to be equal to or in excess of 12％, the value believed to be the minimum to support forest fires (Chaloner, 1989 and Wildman et al., 2004b). 〔Berner,R.A.(2006): GEOCARBSULF: A combined model for Phanerozoic atmospheric O2 and CO2. Geochimica et Cosmochimica Acta, 70, 5653-5664.から〕

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