GRAIN SIZE AND SHAPE DISTRIBUTIONS, GRAIN PACKING, AND PORE GEOMETRY WITHIN SAND LAMINAE: CHARACTERIZATION AND METHODOLOGIES

The principal objective of this study was to develop a battery of methodologies for the analysis of texture, grain packing and pore geometry in sands and sandstones. The methodologies developed include: (1) the 'roller micrometer', a machine which sizes grains by their smallest dimension, S; (2) plots of the joint I:S size and S/I form distributions (I is the intermediate grain dimension determined by sieving); (3) a sorting comparator for the visual estimation of sorting in thin sections; (4) 'packing efficiency', the ratio of minimum compactional to depositional porosity; (5) 'floating index', the proportion of grains lacking intergranular contacts; (6) correction of measurement errors in standard thin section packing analyses; (7) transformation, via digitization, of plain sections of samples into matrices of binary (rock vs pore) numbers; and (8) computer processing of the rock-pore matrices using the Fortran IV program PORESTAT which measures numerous parameters including porosity, specific pore surface area, pore size distribution, pore tortuosity, pore orientation, and periodic repetitions in the pore pattern.; Additionally, several new approaches to the hydraulic interpretation of textural data, sampling and sample preparation, and correlation analysis of bivariate data are developed. Two of the more important developments are: a new empirical prediction equation for the settling velocity of nonspherical grains; and a Fortran IV computer program, CORMAT, which produces a correlation matrix describing the strength and character of bivariate curvilinear relationships.; Twenty-eight samples of single laminae were collected from modern and ancient lacustrine and marine beach, eolian dune, and fluvial channel environments. Loose grain fractions and thin sections were obtained for each sample. The loose grains were subjected to textural and packing analyses, and the thin sections were subjected to pore geometry and packing analyses. The samples were collected and analyzed in order to evaluate the methodologies developed in this study. The analyses are too few in number to permit sedimentologic conclusions to be drawn about the sampled depositional environments. The analyses are important, however, in that they represent the first comprehensive characterization of single sand laminae.