Carbon speciation in organic fossils using 2D to 3D x-ray Raman multispectral imaging

Rafaella Georgiou (1, 2) , Pierre Gueriau (1, 3) , Christoph Sahle (4) , Sylvain Bernard (5) , Alessandro Mirone (4) , Romain Garrouste (6) , Uwe Bergmann (7) , Jean-Pascal Rueff (2, 8) , Loïc Bertrand (1, 2)

1 IPANEMA - Institut photonique d'analyse non-destructive européen des matériaux anciens
2 SSOLEIL - Synchrotron SOLEIL
3 UNIL - Université de Lausanne = University of Lausanne
4 ESRF - European Synchrotron Radiation Facility
5 IMPMC - Institut de minéralogie, de physique des matériaux et de cosmochimie
6 ISYEB - Institut de Systématique, Evolution, Biodiversité
7 Stanford PULSE Center
8 LCPMR - Laboratoire de Chimie Physique - Matière et Rayonnement

The in situ two-dimensional (2D) and 3D imaging of the chemical speciation of organic fossils is an unsolved problem in paleontology and cultural heritage. Here, we use x-ray Raman scattering (XRS)-based imaging at the carbon K-edge to form 2D and 3D images of the carbon chemistry in two exceptionally preserved specimens, a fossil plant dating back from the Carboniferous and an ancient insect entrapped in 53-million-year-old amber. The 2D XRS imaging of the plant fossil reveals a homogeneous chemical composition with micrometric "pockets" of preservation, likely inherited from its geological history. The 3D XRS imaging of the insect cuticle displays an exceptionally well preserved remaining chemical signature typical of polysaccharides such as chitin around a largely hollowed-out inclusion. Our results open up new perspectives for in situ chemical speciation imaging of fossilized organic materials, with the potential to enhance our understanding of organic specimens and their paleobiology.

Keywords: Spectral imaging; Ant; Insect; Amber; X-ray; Raman; Paleontology

Domains: Paleontology; Material chemistry; Physics [physics]; Cultural heritage and museology; Chemical Physics [physics.chem-ph]; Analytical chemistry

Rafaella Georgiou, Pierre Gueriau, Christoph Sahle, Sylvain Bernard, Alessandro Mirone, et al.. Carbon speciation in organic fossils using 2D to 3D x-ray Raman multispectral imaging. Science Advances , 2019, 5 (8), pp.eaaw5019. ⟨10.1126/sciadv.aaw5019⟩. ⟨hal-02288211⟩