A technique for processing undisturbed marine sand sediments and reconstructing fabric and porometry
Study of marine sediment pore fluid pathways and porometry requires careful analysis of the fabric of "undisturbed" sediment samples. A novel solution to the preservation of the interstitial organic material and the in situ fabric or sedimentary structure is the application, with little modification, of well-established biological techniques employing agar infiltration. The solidified agar preserves fabric during subsequent epoxy impregnation. Once impregnated, porosity of the samples can be measured using image analysis of polished surfaces of the microfabric and/or a gravimetric-volumetric technique. Porosity was about 10% higher with image analysis, apparently because of problems in visualizing carbonates and edges of grains. Tortuosity was measured as a function of pathlength ratios taken in stacked planes of microfabric images. The technique allowed us to detect variability in directional tortuosity as a function of orthogonal pathlength ratios. Three-dimensional stacking of digitally acquired wireframe images of sequential planes through the microfabric allows visualization of long continuous pores, some with 2.6 Barn length.