VISUALIZATION OF THREE-DIMENSIONALLY RECONSTRUCTED MARINE CLAY FABRIC AT THE NANO- AND MICROMETER SCALE

Clay fabric (defined as the spatial distribution, orientations, and particle-to-particle relations of the solid particles) has been of scientific and engineering interest since the work of Terzaghi (1925) and Casagrande (1932). Various early models were proposed (Terzaghi-Casagrande Honeycomb Model; Goldschmidt 1926, Lambe 1953, and Tan 1957) to explain the physical and mechanical properties of the soils and sediment but a significant refinement of clay particles and fabric models emerged with the advancement of transmission electron microscopy (TEM) that provided high resolution visualization of clay fabric (Rosenqvist 1959). Later, clay fabric models evolved with concepts that increasingly coupled function with structure based upon two-dimensional TEM images (Bennett et al. 1977, 1981). Technological advances in computer capabilities and computer software are providing us with three-dimensional image analysis of clay fabric at nano- and microscales. Historically, fabric analysis using 2-D representations addressed physical properties such as porosity, void ratio, and particle size distribution, particle shape, and fabric signatures. Important properties such as 3-D particle orientation, tortuosity, and the distinction between effective and inaccessible porosity have remained elusive. Presently, image analysis software can be applied to nanoscale 3-D reconstruction techniques, allowing us to visualize and study quantitatively previously elusive properties at the nanometer scale of organization and to refine and improve models of clay fabric from a volumetric perspective. Three-dimensional techniques using tomography and scanning electron microscopy (Keller et al. 2011) are showing the promise of 3-D technology, but TEM technology provides the highest level of resolution presently achievable. We present three-dimensional images and conceptualizations of particle orientation, porosity, and tortuosity with quantitative and qualitative analyses. 3-D fabric analysis at different nanometer sampling scales (300 – 1000 nm cubes) of the same reconstructed sediment led to somewhat different quantitative interpretation for some of the parameters we measured. This suggests that important differences in clay fabric and morphology are nested at different scales of organization.