LAB DATA CORRELATIONS WITH FIELD OBSERVATIONS IN AFGHANISTAN SOILS

Shallow soil stratigraphy and its relationship to soil properties were investigated at 12 sites in Afghanistan with variable geologic settings. Field teams collected discrete soil samples at the ground surface down to a depth of 2 meters. Simultaneously, the in-situ stratigraphy of each excavated trench was logged. Lab tests such as magnetic susceptibility, moisture contents, and x-ray diffraction were performed to obtain an understanding of the undisturbed soil properties. Challenges associated with the interpretation of aridisols include an understanding of evaporative mineralogy as well as elevated erosion and sedimentation rates caused by intense and sporadic rainfall events. However, these challenges prove to be beneficial in identifying disturbances. When the ground surface is disturbed, evaporite minerals such as halite and gypsum show changes in soil properties. The identification of the evaporite minerals and expansive clays provide a complete understanding of the geology, the environment of the area from which the samples were collected, and whether the soil has been disturbed. Laboratory results were compared to the documented soils stratigraphy in the field logs. Representative sites were selected to show a correlation between soil properties and field data. The sites include calcite-rich and gypsum-rich environments.