Application of IBA to taphonomy and paleontology

(1) PMR-LARN, Department of Physics, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
(2) Department of Geology, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium
(3) Directorate ‘Earth and History of Life’, Royal Belgian Institute of Natural Sciences, rue Vautier 29, 1000 Brussels, Belgium

Recent discoveries of fossil feathers preserved with some theropod skeletons provided new insights on the origin of the plumage in non-avian dinosaurs. In this study, we performed geochemical analysis on fossil feathers in order to characterize their composition and, therefore, their preservation state. The fossil soft tissues are preserved around the skeleton of a new specimen of the Jurassic paravian theropod Anchiornis huxleyi. Feather chemistry has been revealed by combining IBA techniques: Proton-Induced X-ray Emission (PIXE), Nuclear Reaction Analysis (NRA) and Rutherford Backscattering (RBS) analysis. By combining NRA, RBS and PIXE induced by deuterons, we demonstrate that it is possible to measure quantitatively light and heavy elements in the fossil feathers as well as in the sediments around the fossil. PIXE and RBS were acquired simultaneously with a proton beam of 3.0 MeV, allowing identifying the elemental composition of the plumage and the surrounding matrix. They both contain elements as C, O, Cu, Cr, Fe and Ca. The melanin pigment found in all extant feathers contains chelated Cu. The presence of such element in the spectrum of the fossil could indicate melanin remains preserved in the Anchiornis plumage. RBS permitted to observe enriched carbon and oxygen layers on the fossil plumage and thus, to differentiate the fossil tissues from the surrounding sediment. The combined analysis showed we can quickly determine the elemental enrichment and depletion, and the structure of the fossil feathers using techniques that are new in the field of paleontology.