[1] Univ Plymouth, Sch Geog Earth & Environm Sci, Plymouth PL4 8AA, Devon, England
[2] Univ Southampton, Natl Oceanog Ctr, Sch Ocean & Earth Sci, Southampton SO14 3ZH, Hants, England
[3] Univ Complutense Madrid, Dept Paleontol, E-28040 Madrid, Spain
[4] Univ Complutense Madrid, Dept Estratig, E-28040 Madrid, Spain
[5] Univ Politecn Madrid, Dept Ingn Geol, Madrid 28003, Spain
[6] Univ Calif Santa Cruz, Dept Earth & Planetary Sci, Santa Cruz, CA 95064 USA
[7] Univ Leicester, Dept Geol, Leicester LE1 7RH, Leics, England
[8] British Geol Survey, NERC, Isotope Geosci Lab, Nottingham NG12 5GG, England
[9] Univ Birmingham, Sch Geog Earth & Environm Sci, Birmingham B15 2TT, W Midlands, England
[10] Univ Bristol, Sch Chem, Cabot Inst, Organ Geochem Unit, Bristol BS8 1TS, Avon, England
[11] Univ Liverpool, Sch Environm Sci, Dept Earth Ocean & Ecol Sci, Liverpool L69 3BX, Merseyside, England