Complex sentence: Rock bodies with differing lithologies have different characteristics of tectonic deformation, and behave in a brittle manner above the décollement surface, with intense ductile deformation below the décollement surface.
Split into simpler sentences: Rock bodies with differing lithologies have different characteristics of tectonic deformation. They can behave in a brittle manner above the décollement surface, with intense ductile deformation below the décollement surface.