Fruit and seed biomineralization and its effect on preservation
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ORIGINAL PAPER
Fruit and seed biomineralization and its effect on preservation Erwan Messager & Aïcha Badou & François Fröhlich & Brigitte Deniaux & David Lordkipanidze & Pierre Voinchet
Received: 8 October 2009 / Accepted: 26 January 2010 / Published online: 13 March 2010 # Springer-Verlag 2010
Abstract Mineralised fruits and seeds are frequently found in archaeological sediments but their chemical nature has not been often examined. The nature and the origin of these archaeobotanical remains have to be investigated to understand their taphonomic history. Fruits or seeds can be mineralised not only by replacement mineralisation but also by biomineralisation during the plant life. The mineral components of three fossil fruits sampled on the Pleistocene site of Dmanisi were analysed and compared with their modern analogues. Analyses were carried out by means of an environmental scanning electron microscope, equipped with an energy dispersive X-ray device and by means of a Fourier transform infrared spectrometer. Biogenic carbonates and/or biogenic silica were identified in the fossil and modern fruits of some taxa. Comparison between fossil and modern specimens has shown that molecular reorganisation occurred in carbonate and in biogenic silica during E. Messager Maison de l’Archéologie et de l’Ethnologie, UMR 7041, ArscAn, 21, allée de l’Université, 92023 Nanterre cedex, France E. Messager (*) : B. Deniaux : P. Voinchet Département de Préhistoire, Muséum national d’Histoire naturelle, UMR 7194, IPH, 1, rue René Panhard, 75013 Paris, France e-mail: [email protected] A. Badou : F. Fröhlich Département de Préhistoire, Muséum national d’Histoire naturelle, UMR 7194, Centre de Spectroscopie Infrarouge, CP 57, 57, rue Cuvier, 75231 Paris cedex 05, France D. Lordkipanidze Georgian National Museum, 3, Rustaveli Avenue, 0105 Tbilisi, Georgia
fossilisation, through diagenetic processes. The resulting stable mineral structures confer an exceptional preservation to fruits in sediments. Taking into account these taphonomic specificities (transformation and differential preservation), the chronological and palaeoenvironmental aspects of the mineralised fruits are discussed. Keywords Fruit remains . Biomineralisation . Taphonomy . X-ray EDS . Scanning electronic environmental microscopy . Fourier transform infrared spectroscopy
Introduction Plant macroremains recovered from archaeological sites are most commonly charred (e.g. fruits, seeds and wood charcoals), which preserves them from decomposition by micro-organisms in various kinds of deposits. However, mineralised botanical remains (Green 1979) often appear in global charred assemblages and do not seem to be linked with the archaeological context, which makes them difficult to be used by archaeobotanists (van Zeist and Buitenhuis 1983; van Zeist and de Roller 1995). Their occurrence in various contexts and stages of preservation raises questions about their origin and taphonomy (McCobb et al. 2001, 2003). Mineralised archaeobotanical remains can be classified into two groups
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