Ages are estimated from delta18O isotope stratigraphy. 'Clean' samples were more thoroughly cleaned with water and methanol. Quoted errors in the 87Sr/86Sr ratio are in the last digit and are the 2 sigma internal statistics for that analysis. These are always less than +/- 0.000009, the long-term repeatability, which is shown in all figures and represents the true uncertainty on the analyses. For Delta 87Sr (ppm) errors shown are the 2 sigma internal error; external repeatability expressed in this form is 13 ppm.