Direct measurement of pore-size distribution on artificial and natural deposits and prediction of pore space accessible to interstitial organisms

The pore spaces and particles comprising (a) 2 artificial sands consisting of uniform spherical particles and (b) 4 natural shell gravels from Church Island, Menai Strait, N. Wales, were observed directly in thin sections. Porosity and granulometry measurements made visually agreed with those obtained by traditional methods. Pore-size distributions could also be measured and always showed greater dispersion than particle-size distributions. In the almost monometric sands, the mean pore diameter was 30 to 40% of the mean particle diameter, in agreement with the Koseny-Carmen equation. In the polymorphic shell gravels, the mean pore size was only 15 to 20% of the mean particle size, and diminished with increased content of fine particles. A theoretical treatment is given, based on a model of interconnecting dilations and constrictions, to allow the proportion of total void space available to an organism of given diameter to be predicted.