Nature Communications 4: Article number: 2466 (2013); Published: 12 September 2013; Updated: 26 November 2013.

The financial support for this article was not fully acknowledged. The Acknowledgements should have included the following:

Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract number DE-AC02-06CH11357. GSECARS at APS is supported by the National Science Foundation Earth Sciences (EAR-0622171) and Department of Energy Geosciences (DE-FG02-94ER14466).