A comparison of grain-size analysis methods for sand-dominated fluvial sediments

Grain-size distribution is a fundamental tool for interpreting sedimentary units within depositional systems. The techniques assessed in this study are commonly used to determine grain-size distributions for sand-dominated sediments. However, the degree of consistency and differences in interpretation when using a combination of grain-size methods have not yet been assessed systematically for sand-dominated fluvial sediments. Results obtained from laser diffraction, X-ray attenuation and scanning electron microscopy grain-size analysis techniques were compared with those obtained from the traditional sieve/ hydrometer method. Scanning electron microscopy was shown to provide an inaccurate quantitative analysis of grain-size distributions because of difficulties in obtaining representative samples for examination. The X-ray attenuation method is unsuitable for sand-dominated sediments because of its upper size range of only 300 μm. The consistently strong correlation between the laser diffraction results and the sieve/ hydrometer results shows that these methods are comparable for sand-dominated fluvial sediments. Provided that sample preparation is consistent, the latter two methods can be used together within a study of such sediments while maintaining a high degree of accuracy. These results indicate that data for sand-dominated fluvial sediments gained from the long-established sieve/hydrometer method can be compared with confidence to those obtained by modern studies using laser diffraction techniques.