ABSTRACT

Although between-laminae parameter variations in sediments have been studied in the past, measured parameters were generally limited to grain-size distribution and total porosity. The magnitude and directional characteristics of physical properties of laminated sediments also depend on the shape and orientation of particles, packing, pore-size characteristics, and properties of the pore network. Leaving out a complete characterization of granular sediment in models of physical properties could result in a systematic mismatch between modeled and measured values. However, tools for high-resolution quantification of these spatial variable parameters are not readily available. In order to provide such a tool, an image-analysis procedure is presented based on digital images of thin sections. The procedure defines a sequence of rectangular measurement windows, with their long sides oriented parallel to stratification, and measures the sediment characteristics for each window. Logs of parameters values, oriented perpendicular to stratification, are thus created. After verification of the image-analysis procedure using comparative laboratory measurements, the procedure is applied to two thin-section images of unconsolidated fine-grained, laminated sands. The quantitative variations observed in the logs of grain and pore characteristics correlate well with bedding observed on the original images. Overall, the image-analysis procedure proved to be a useful and versatile tool for quantifying variations of textural characteristics on sub-lamina scale.