Which tool is used to graphically delineate soil textural classes?

The USDA soil textural triangle is the correct tool for graphically delineating soil textural classes. This triangle is a visual representation used to determine the texture of soil based on the proportions of sand, silt, and clay present. By plotting the percentages of these three components on the triangular diagram, users can easily identify the specific soil textural class, such as sandy loam, clay, or silty clay.

Other options like the soil classification chart and soil texture diagram may provide valuable information related to soil types, but they do not serve the same purpose as the USDA soil textural triangle. A soil stratification map typically represents variations in soil layers and their characteristics, rather than focusing on the textural classification based on particle size distribution. This specificity of the USDA triangle makes it the preferred and recognized tool for delineating soil textural classes in soil science.