Paleontological Museum of Empoli

In the hall of the Pliocene in Tuscany, important collections are presented of Pliocene mollusks from various fossiliferous locations. One of the places included among these is the former clay quarry of Spicchio sull'Arno. The fossils of Spicchio conserved in the museum's collection are the same as those observed by Leonardo in the so-called "Collegonzi cut", an exposed geological section that was located near Spicchio and which Leonardo described in various passages of the Codex Leicester. In fact, Leonardo had observed the different layers of the geological formations of the Valdarno, recognizing therein the results of the action of the Pliocene sea on what were, at that time, its ancient shores. In particular, he recognized the succession of geological strata of different compositions, from coarsest to finest: "minute gravel", "sand", and finally "mud", the thinnest and lightest, which once formed the bottom of Pliocene sea. The raising of the seabed and its subsequent drying up had given rise, for Leonardo, to that particular formation composed of alternating layers of bluish mud and nichi, the fossil shells he observed and found in great quantity in the area of ​​Spicchio. The reconstruction of the geological stratigraphy of the Middle Valdarno, exhibited in the "Hall of the Pliocene in Tuscany", evokes Leonardo’s descriptions of the layers of gravels, sands, and muds rich in marine fossils from his studies of geology and paleontology in the Codex Leicester.