Heritage Cases

I request permission to send 50 coprolite specimens, with min/max lengths of >1mm–70mm and min/max diameters of <1mm–40mm (See attached figure), from the farm Driefontein 11 in the Free State to the European Synchrotron and Radiation Facility in Grenoble, France, for high-resolution scanning. They have cylindrical or spherical morphologies well-suited for tomographic scanning, and will be mounted vertically in acrylic tubular housing so that they can be batch-scanned, a technique already employed by the ESRF for other fossils The samples will be scanned in two sets of experiments using propagation phase-contrast synchrotron radiation microtomography at beamline BM18. Phase contrast imaging is required to discriminate between the subtle density differences between material inclusions and groundmass of the coprolites, which are indiscernible given lab micro-CT scans. Conventional thin sectioning of the coprolites is not feasible for this analysis because the preserved inclusions and internal fabrics need to be visualized in 3 dimensions for identification. The largest samples will be scanned at a resolution that will incorporate the complete sample in the field of view in half-acquisition mode and then increasing resolution to incorporate smaller samples in the field of view in half-acquisition mode. Scanning will proceed at three different voxel sizes, ~6 μm for a complete scan of larger specimens, and ~2.2μm for smaller specimens. The experiment needs to be partitioned into 2 sessions to allow localization of regions of interest to scan at higher resolution such as important microfossil inclusions. The second experimental session will be scheduled about five months after the first to allow reconstruction of the data and identification of ROI’s for scanning at higher resolutions. Work done on the requested specimens will form part on my PhD research. Some of these have previously been scanned using the in-house micro-CT facility of the Evolutionary Studies Institute at University of the Witwatersrand and shown to have myriad fossil inclusions. These scans however did not provide detail sufficient for taxonomic identification or fully characterising the anatomy. Our aim is therefore to have the specimens scanned at higher resolution to develop 3D digital visualizations of these inclusions others to identify them at more precise taxonomic levels, and to use material cross-sections and three-dimensional properties to study the fabric of the coprolites to determine their origins.