Relationship between fluvial bounding surfaces and the permeability correlation structure

Results of three meter-scale outcrop studies suggest a quantifiable relationship between fluvial bounding surfaces and the permeability correlation structure, mapping of bounding surfaces and in situ measurements of permeability were obtained in three types of deposits: a low-energy channel deposit, a paleosol, and a high-energy channel-deposit. For the low-energy channel deposit only second-order surfaces separating lithofacies were mapped. The variogram exhibits anisotropic exponential behavior, and an analysis of variance (ANOVA) suggests that the within-facies variation dominates over between-facies variation. The paleosol contained no internal bounding surfaces and exhibited a ''bell-shaped'' variogram consistent with a smoothly varying style of heterogeneity. Both first- and second-order bounding surfaces were mapped in the high-energy channel deposit. Results of the ANOVA suggest that the between-facies variation dominates over the within-facies variation. A model of spatial correlation using superposition of independent processes acting over different scales provides a good fit to the data. These three studies suggest that fluvial bounding surfaces provide a geological basis for conceptualizing and modeling heterogeneity in alluvial deposits.