Complex sentence: Clay and sand are the predominant formations, the watercourses, especially in the north, being frequently excavated deep, and in many places in the flat, dry valleys or depressions farther south beds of loess, thick, are exposed.
Split into simpler sentences: Clay and sand are the predominant formations; the watercourses, especially in the north, being frequently excavated deep. In many places in the flat, dry valleys or depressions farther south, beds of loess, thick, are exposed.