Quaternary Science Reviews 22 (2003) 1805–1812 Radiocarbon dating of organic- and carbonate-carbon in Genyornis and Dromaius eggshell using stepped combustion and stepped acidification M.I. Bird a,b, *, C.S.M. Turney a,1 , L.K. Fifield c , M.A. Smith d , G.H. Miller e,f , R.G. Roberts g , J.W. Magee h a Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia b Research School of Biological Sciences, Australian National University, Canberra, ACT 0200, Australia c Department of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia d Research and Development Section, National Museum of Australia, Canberra, ACT 2601, Australia e Centre for Geochronological Research, Institute of Arctic and Alpine Research, University of Colorado, Campos Box 450, Boulder, CO 80309-0450, USA f Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0450, USA g School of Geosciences, University of Wollongong, Wollongong NSW 2522, Australia h Department of Geology, Australian National University, Canberra, ACT 0200, Australia Received 18 August 2002; accepted 12 May 2003 Abstract A technique for determining the radiocarbon age of both organic-carbon and carbonate-carbon in the eggshell of the large flightless birds Genyornis newtoni (now extinct) and Dromaius novaehollandiae (extant emu) is presented here. Stepped combustion (for organic-carbon) and stepped acidification (for carbonate-carbon) were used to obtain multiple age determinations for each sample, from which an assessment of the reliability of the ages is possible. Analysis of a Genyornis newtoni eggshell fragment known to have an age considerably beyond the limit of radiocarbon dating has indicated that the backgrounds obtainable using this approach are 0.12270.033 pMC for the organic-carbon fraction and 0.07070.025 pMC for the carbonate-carbon fraction. These backgrounds suggest that finite ages up to 50,000–55,000 BP are readily achievable on eggshell using stepped combustion/acidification. Analysis of a single fragment of Genyornis eggshell from Williams Point, central South Australia, suggests that significant contamination of the organic-carbon fraction of the eggshell is possible, while ages for the carbonate fraction appear more reliable and indicate that the eggshell has an age of at least 49,00072000 BP. A total of six analyses of single Genyornis newtoni and Dromaius novaehollandiae eggshell fragments from the Wood Point deposit in southern South Australia suggest ages for the samples of 41,0007800 and 37,9007700 BP, respectively, while an optically stimulated luminescence (OSL) sample from a location very close to the Genyornis sample has an age of 5575 ka (1s). The OSL and calibrated radiocarbon ages for the Genyornis sample and the sand matrix overlap at two standard deviations, suggesting the most likely age for the eggshell and the sand matrix is B45 cal ka BP or earlier. r 2003 Published by Elsevier Science Ltd. 1. Introduction The eggshells of large, flightless birds such as the extant emu and ostrich have been shown to be suitable for dating by a variety of techniques including radio- carbon, uranium-series and amino acid racemization (Miller et al., 1999; Vogel et al., 2001). In addition, the stable carbon-isotope composition of carbonate (calcite) and organic-carbon in the shell material has been shown to contain a valuable record of environmental condi- tions (Johnson et al., 1997, 1998, 1999). Recent work has led to doubts about the reliability of radiocarbon ages on eggshell older than B40,000 years because, in some cases, radiocarbon ages on eggshell have been found to ARTICLE IN PRESS *Corresponding author. Present address: National Institute of Education, Nanyang Technological University, 1 Nanyang Walk 637616, Singapore. E-mail address: mibird@nie.edu.sg (M.I. Bird). 1 Present address: School of Archaeology and Palaeoecology, Queen’s University, Belfast, BT7 1NN, Northern Ireland. 0277-3791/03/$ - see front matter r 2003 Published by Elsevier Science Ltd. doi:10.1016/S0277-3791(03)00151-3