THE RELATIONSHIP BETWEEN LITHOLOGY AND SLOPE FORM IN THE TUCSON MOUNTAINS, PIMA COUNTY, ARIZONA

Abstract

The relationship between lithology and slope morphology is investigated at eight sites on granitic, andesitic, and sedimentary rock slopes in the Tucson Mountains. Several methods are used in the study. Topographic profiles are constructed. Skewness indices of the slope shapes, maximum and minimum slope angles, and slope lengths of the different slope profiles are computed and compared with each other. Debris size analysis is done to better determine hillfront/piedmont junctions. Slope surface regularities of the three lithological slopes are analysed and compared. The results show that the granitic piedmont slopes are found to be slightly concave to almost rectilinear, indicating their high resistance to erosive processes. In contrast, the concavity of the andesitic and sedimentary piedmont slopes demonstrate their inability to resist the erosive attack on them. However, in the case of the hillfront slopes, slope forms do not reflect lithological variations.