1ICAR Project Team, LIRMM, CNRS/University Montpellier 2, France, 2Curation Dept., Museum of Toulouse, France, 3IMA Solutions, Toulouse, France, 4SHAMAN Project Team, INRIA Lille Nord Europe, France, 5AMIS Laboratory, CNRS/University of Toulouse, France, 6VORTEX Project Team, IRIT, CNRS/University of Toulouse, France
Saturday 165, Plaza Level
One of the main difficulties in studying unearthed human fossils is that they have often undergone plastic deformation due to the slow movement of the surrounding geological layers, the increasing compression of the sediments that piled-up onto them, and more generally the diagenetic phenomena.
To investigate this issue, we designed a test-bed to simulate a fossilization process leading to a plastic deformation. We took a bony structure, plunged it into an acid liquid and applied a controlled mechanical load by using a calibrated weight. The bony structure then deformed plastically and 3D data are acquired regularly by using a surface laser-scanner or a volume CT scanner. This results in a time-series of 3D data representing the shape of the bony structure at different states of deformation.
3D image processing algorithms were applied to segment the external surface of the “fossil” in each 3D data of the time-series and to find automatically the point correspondences between the successive 3D surfaces. The resulting 3D displacement fields characterize the plastic deformation due to the “fossilization” process.
We used the SOFA software to build a mechanical model of the bony structure. This software proposes also several algorithms for describing various sets of constraints (pressure constraints, unilateral constraints, etc.) and it is particularly adapted for rapidly testing combinations of methods. By fitting the models of the structure and of the constraints to the observed 3D displacement field, we inferred some biomechanical laws which characterize a plastic fossilization process
Thanks to Brian Aiello and Benoït Gransac for their valuable help. This research is supported by the French Center for Scientific Research (PEPS FOSSPROPALE Project).