Nomenclature Based on Sand-silt-clay Ratios

ABSTRACT Following a canvassing of sedimentationists an attempt is made to standardize nomenclature of sediment types relative to sand, silt, and clay content. A triangle diagram with boundaries between types, which met with general approval, is submitted and compared with other systems which have been used for the purpose. The new system uses old well established names and has a simplicity and symmetry which make it easily remembered. The boundaries appear to be well located for description of sediments such as those that have been analyzed in large volume from the investigations of the northern Gulf of Mexico (API Project 51), but it is inadequate in describing well sorted sediments with median diameters near the boundaries of sand and silt or silt and clay. The nomenclature suggested applie only to sediment grade sizes so that other names should be used depending on other characteristics of the sediments. Furthermore, the nomenclature should not be applied to sediments containing large percentages of gravel.