The marls and limestone benches along this path are very rich in fossils. These sedimentary lands were formed about 200 million years ago.Gray marls are lands unsuitable for cultivation but contain treasures of natural heritage: Jurassic marine fossils (belemnites).Marls are sedimentary rocks, composed of calcite and clay in roughly equivalent proportions (35% to 65%).On this path, we can also find pyrite (comes from Greek: fire-stone), a mineral composed of iron disulfide.