Marine chronology based on 14 C dating on diatoms proteins Christine Hatté a,b, ⁎ , Gregory Hodgins a , A.J. Timothy Jull a , Bongi Bishop a , Benoit Tesson c a NSFArizona AMS Laboratory, Physics Building, Univ. of Arizona, 1118 East Fourth St, Tucson, AZ 85721, USA b LSCE, UMR CEA-CNRS-UVSQ 1572, Domaine du CNRS, F-91198 Gif-sur-Yvette Cedex, France c ISOMer - Laboratoire de Biologie Marine, UPRES EA 2663 “Ecophysiologie Marine Intégrée”, Université de Nantes, 2 rue de la Houssinière, BP 92208, F-44322 NANTES Cedex 03, France Received 15 June 2007; received in revised form 19 December 2007 Available online 16 January 2008 Abstract We present a new method of obtaining radiocarbon dates for proteins intrinsic to diatom frustules (sillafin). By asserting age models for sediment core samples that lack calcium carbonate, this method will improve interpretations of diatom-based paleoproxies for either marine or lacustrine. In preparation for radiocarbon dating by Accelerator Mass Spectrometry, diatoms were concentrated from core sediment samples. The diatoms frustules were freed of any surface-bound organic matter, through chemical and physical treatments that will be discussed later in this paper. Compounds intrinsic to diatoms frustules were released from their opal matrix by HF dissolution. This method differs from approaches based on specific compound extractions from complex organic mixture by preparative chromatography because we eliminated most of the contaminated organic matter. The advantage of our method is that it does not require heavy cost investment and it can be added to a preparative chromatography protocol to ensure dating reliability. This method was applied to samples from a marine core collected in the Southern Ocean, that spans the last climatic cycle. We report on the radiocarbon dating results obtained on organic matter at each step of the chemical treatment, from bulk to sillafin and their interpretation. © 2008 Elsevier B.V. All rights reserved. Keywords: Diatom-bound organic matter; Proteins; 14 C geochronology 1. Introduction Marine sediments provide key records of paleoenvir- onmental and paleoclimatic changes, but interpretation of these records depends greatly on the accuracy in which we can constrain core chronologies. Radiocarbon dating of foraminifera calcium carbonate is a common method for determining the age of Holocene and Upper Pleistocene age sediments. This method relies on the presence of foraminifera in the sediment and on the assumption that foraminifera age reflects the age of other sedimentary components. However, many sedimentary deposits in the Southern Ocean and other laminated sediments lack calcium carbonate. Attempts to use organic sediment material as 14 C support were performed (Rabouille et al., 2002) but they struggled with the heterogeneous nature of the source organic matter. Also, recent studies have shown leads and lags between foraminifera based 14 C obtained from phytoplankton-derived organic compounds. This demonstrates that radiocarbon chronologies based on Available online at www.sciencedirect.com Marine Chemistry 109 (2008) 143 – 151 www.elsevier.com/locate/marchem ⁎ Corresponding author. LSCE, UMR CEA-CNRS-UVSQ 1572, Domaine du CNRS, F-91198 Gif-sur-Yvette Cedex, France. E-mail address: hatte@lsce.ipsl.fr (C. Hatté). 0304-4203/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.marchem.2007.12.008