A WEATHERING SCORE FOR SANDY SOIL MATERIALS BASED ON THE INTENSITY OFETCHING OF QUARTZ GRAINS

A semi-quantitative method is developed to assess the relative weather ing of tropical sandy soils. Individual quartz sand grains are classif ied on the frequency and the size of dissolution etch pits in their su rfaces, using scanning electron microscopy (SEM). A scale with five gr ain-type classes reflecting increasing intensity of etching is defined , and the relative frequency of each of these classes in horizons of s elected soil profiles is determined. To summarize the information cont ained in the frequency distribution a weighted score, the weathering s core, is calculated. This score assesses the relative weathering of in dividual horizons, and it makes it easy to compare them with other hor izons within the same or from other profiles. It is useful in detectin g weathering trends and differences between horizons of tropical sandy soils.