| Summary: | A uranium-lead zircon age for a volcanic ash interstratified with fossil-bearing, shallow marine siliciclastic rocks in the Zimnie Gory section of the White Sea region indicates that a diverse assemblage of body and trace fossils occurred before 555.3 ± 0.3 million years ago. This age is a minimum for the oldest well-documented triploblastic bilaterian Kimberella. It also makes co-occurring trace fossils the oldest that are reliably dated. This determination of age implies that there is no simple relation between Ediacaran diversity and the carbon isotopic composition of Neoproterozoic seawater. © 2000 American Association for the Advancement of Science. Received 15 December 1999; accepted 14 March 2000. We acknowledge support from NSF (grants EAR97-25727 to S.A.B. and EAR94-18523 to J.L.K. and a graduate research fellowship to D.A.D.E.), the Russian Fund for Basic Research (grant 99-05-64547 to M.A.F.), and the National Geographic Society (grant 6015-97 to M.A.F.). We thank P. Enos, D. Erwin, A. Knoll, W. Hagadorn, B. Hanson, E. Landing, P. Myrow, and one anonymous reviewer for helpful and critical comments on earlier versions of this manuscript. Photographs of Zimnie Gory body and trace fossils were taken by A. Bronnikov.
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