New Lu^Hf and Pb^Pb age constraints on the earliest animal fossils Gry H. Barfod a;b;  , Francis Albare 'de c , Andrew H. Knoll d , Shuhai Xiao e , Philippe Te ¤louk c , Robert Frei a;b , Joel Baker a a Danish Lithosphere Centre, Òster Voldgade 10, L, 1350 Copenhagen, Denmark b Geological Institute, University of Copenhagen, Òster Voldgade 10, 1350 Copenhagen K, Denmark c Ecole Normale Supe ¤rieure de Lyon, 46 Alle ¤e d’Italie, 69364 Lyon Cedex 7, France d Botanical Museum, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA e Department of Geology, Tulane University, New Orleans, LA 70118, USA Received 18 December 2001; received in revised form 15 April 2002; accepted 19 April 2002 Abstract The Neoproterozoic Doushantuo Formation, South China, preserves a unique assemblage of early multicellular fossils and overlies rocks, which are thought to have formed during an ice age of global extent. The age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the Proterozoic Eon. Until now, direct dating of sedimentary formations such as the Doushantuo has been difficult and associated with large uncertainties. Here, we show that dating of Doushantuo phosphorites by a novel Lu^Hf dating method and conventional Pb^Pb geochronometry independently yield ages of 584þ26 Ma and 599.3þ4.2 Ma, respectively. These ages are in agreement with bio- and chemostratigraphical observations and show that the Doushantuo animal remains predate diverse Ediacaran fossil assemblages, making them the oldest unambiguous remains of metazoans currently known. Furthermore, the Pb^Pb age for the post-glacial Doushantuo rocks suggests that the Neoproterozoic glaciation in China might predate glacial rocks in Eastern North America commonlyassociatedwiththeyounger(Marinoan)oftwomajorNeoproterozoicglaciations.ThecombinationofLu^ Hf and Pb^Pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on Proterozoic biological and environmental history. ß 2002 Elsevier Science B.V. All rights reserved. Keywords: absolute age; biologic evolution; Doushantuo Formation; Guizhou China; Lu^Hf system; Neoproterozoic; Pb/Pb; phosphate rocks; geochronology; Sinian 1. Introduction The ages of Phanerozoic sedimentary forma- tions are conventionally estimated from indirect methods based on bio- and chemostratigraphy. Combined, these form a geochronological frame- work,whichiscalibratedbyU^Pbzircondatesas 0012-821X/02/$ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII:S0012-821X(02)00687-8 * Corresponding author, at address a. Tel.: +45-3-814-2663; Fax: +45-3-311-0878. E-mail address: ghb@dlc.ku.dk (G.H. Barfod). Earth and Planetary Science Letters 201 (2002) 203^212 www.elsevier.com/locate/epsl