Preliminary microfocus X-ray computed tomography survey of echinoid fossil microstructure
S. R. Stock, A. Veis, 2003. "Preliminary microfocus X-ray computed tomography survey of echinoid fossil microstructure", Applications of X-ray Computed Tomography in the Geosciences, F. Mees, R. Swennen, M. Van Geet, P. Jacobs
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Microfocus X-ray computed tomography (μCT), a high resolution variant of medical CT, was used to non-invasively examine Jurassic echinoid fossils with spine, demipyramid and test plate fragments serving to assess the extent to which the microstructure remained unaffected by diagenesis. The sizes of the calcite-crystal stereom remains dictated the resolution that could be obtained. The smaller diameter spines were imaged with 9× 9 × c. 25 μm voxels; the larger demipyramids and test plate fragments were imaged with 13 × 13 μm and 17 × 17μm voxels, respectively, in the plane of reconstruction and with a proportionally larger slice thickness. The stereom structure was not seen in the μCT slices of the fossils. This is not surprising because, for the ossicles studied, the stereom pore dimensions are, for the most part, smaller than the resolution of the μCT system. Tide marks and other low absorption features were found in the spines and appear to be related to diagenetic changes. What appear to be cleavage cracks were observed in the demipyramid and some of the pores for tube feet could be seen in the test fragment.
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X-ray computed tomography (CT) is a technique that allows non-destructive imaging and quantification of internal features of objects. It was originally developed as a medical imaging technique, but it is now also becoming widely used for the study of materials in engineering and the geosciences. X-ray CT reveals differences in density and atomic composition and can therefore be used for the study of porosity, the relative distribution of contrasting solid phases and the penetration of injected solutions. As a non-destructive technique, it is ideally suited for monitoring of processes, such as the movement of solutions and the behaviour of materials under compression. Because large numbers of parallel two-dimensional cross-sections can be obtained, three-dimensional representations of selected features can be created. In this book, various applications of X-ray CT in the geosciences are illustrated by papers covering a wide range of disciplines, including petrology, soil science, petroleum geology, geomechanics and sedimentology.