Abstract
Ancient dune sand environments in deserts and coasts are aquifers and hydrocarbon reservoirs that commonly have preserved high permeability (hydraulic conductivity). A paucity of research has been performed on variations in the distribution of permeability associated with the positions within the dunes and the differences between these patterns in desert and coastal dunes. A comparison of dune sand grain size and hydraulic properties of a desert barchan dune field in Saudi Arabia to a coastal dune field in Uruguay has revealed some important differences and similarities. The grain size characteristics show that the mean grain diameter was significantly lower in the barchan dune field compared to the coastal dune field (1.95-2.79 phi) and the sorting was better in the coastal dune field (0.40-0.66 phi). The skewness and kurtosis of the dune sands were not significantly different with the skewness < 0.1 and the kurtosis near 1.0. No statistical differences based on dune position were found in the coastal dunes, but there were significant differences in position in the desert dunes. The porosity differed between the desert dunes and the coastal dunes with the mean values being 0.39 and 0.35 respectively. No significant porosity variation with dune position was found in either dune type. The coastal dunes had a significantly higher mean hydraulic conductivity of 25.3 m/d compared to the desert dunes of 9.32 m/d. The dune crests in the desert dunes had significantly higher hydraulic conductivity values compared to other locations in the dune profile.