Blattler（aの頭に¨）,C.L., Jenkyns,H.C., Reynard,L.M. and Henderson,G.M.(2011): Significant increases in global weathering during Oceanic Anoxic Events 1a and 2 indicated by calcium isotopes. Earth and Planetary Science Letters, 309, 77-88.

『カルシウム同位体により示された海洋無酸素事変1aと2の間の世界的な風化の重大な増加』

『Abstract
　Calcium-isotope ratios (δ44/42Ca) were measured in carbonate-rich sedimentary sections deposited during Oceanic Anoxic Events 1a (Early Aptian) and 2 (Cenomanian-Turonian). In sections from Resolution Guyot, Mid-Pacific Mountains; Coppitella, Italy; and the English Chalk at Eastbourne and South Ferriby, UK, a negative excursion in δ44/42Ca of 〜0.20‰ and 〜0.10‰ is observed for the two events. These δ44/42Ca excursions occur at the same stratigraphic level as the carbon-isotope excursions that define the events, but do not correlate with evidence for carbonate dissolution or lithological changes. Diagenetic and temperature effects on the calcium-isotope ratios can be discounted, leaving changes in global seawater composition as the most probable explanation for δ44/42Ca changes in four different carbonate sections. an oceanic box model with coupled strontium- and calcium-isotope systems indicates that a global weathering increase is likely to be the dominant driver of transient excursions in calcium-isotope ratios. The model suggests that contributions from hydrothermal activity and carbonate dissolution are too small and short-lived to affect the oceanic calcium reservoir measurably. a modelled increase in weathering flux, on the order of three times the modern flux, combined with increased hydrothermal activity due to formation of the Ontong-Java Plateau (OAE 1a) and Caribbean Plateau (OAE 2), can produce trends in both calcium and strontium isotopes that match the signals recorded in the carbonate sections. This study presents the first major-element record of a weathering response to Oceanic Anoxic Events.

Keywords: calcium isotopes; OAE; weathering; Cretaceous』

1. Introduction
2. Background
3. Samples
　3.1. Oceanic Anoxic Event 1a: ODP Leg 143, Site 866, Resolution Guyot, Mid-Pacific Mountains
　3.2. Oceanic Anoxic Event 1a: Coppitella, Gargano, Italy
　3.3. Oceanic Anoxic Event 2: Eastbourne, UK
　3.4. Oceanic Anoxic Event 2: South Ferriby, UK
　3.5. Comments on the studied sections
4. Methods
5. Results
6. Discussion
　6.1. Observed δ44/42Ca variation attributed to changing seawater composition
　6.2. Modelling seawater calcium-isotope excursions
　6.3. Quantitatively exploring the weathering response to OAEs
7. Conclusions
Acknowledgements
Appendix A. Supplementary data
References

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