The origin of the rock formations of the area of Sasso Malascarpa can be linked to marine sedimentation phenomena. If you observe the Valmadrera area, you might notice a showy tectonic fold of fossil dolomia in Conchodon, including in the rich series of Rhaetic limestone elements rich in fossils, madrepores, white corals looking like small branching trees. The mainly carbonate composition of the fractured horizons favors the development of karstic phenomena, which are highlighted on the surface by the characteristic "limestone pavement" situated under Mt. Prasanto; they are vertical furrows in the rock, deep and narrow, shaped by the erosive action of the meteoric waters. In the highest part of the area there are showy white slabs of limestone, called Sasso Malascarpa. The slabs are cut into regularly arranged cubes, given by horizontal and vertical fractures crossing with a right angle. On the surface you can admire a considerable quantity of Conchodon fossils, shells of sea mollusks with two curved valves.