[1] Univ Nebraska, Dept Earth & Atmospher Sci, 126 Bessey Hall, Lincoln, NE 68588 USA
[2] Univ Texas Arlington, Dept Earth & Environm Sci, 107 Geosci Bldg,500 Yates St, Arlington, TX 76019 USA
[3] Swedish Museum Nat Hist, Dept Palaeobiol, Box 50007, S-10405 Stockholm, Sweden
[4] 72 Ellendon St, Bungendore, NSW 2621, Australia
[5] Bocking Associates, 8 Tahlee Close, Castle Hill, NSW 2154, Australia
[6] Boise State Univ, Isotope Geol Lab, 1910 Univ Dr, Boise, ID 83725 USA