Le Arenarie di Ponsano a Orgiaglia

The Ponsano Sandstones, which outcrop precisely in the Orgiaglia area, are what remains of an ancient seabed. This environment formed between the Serravallian and Tortonian stages, approximately 11 million years ago, during the geological period called the Miocene: it was a warm, tropical sea rich in life. At that time, the area we are in today was occupied by a vast submarine plain, constantly submerged and therefore not influenced by tides. The depth of the sea could reach 40 meters or a little more; it is probable that the mouth of a river was also nearby.

Also in the Ponsano Sandstones, scientists have found and described the mandible of a whale belonging to the Cethotheriidae family, a group of small cetaceans already known in the Mediterranean basin, but never observed in such an exceptionally preserved state as the specimen found in Orgiaglia. This information was obtained thanks to the numerous fossils preserved in the sandy layers of the Ponsano Sandstones, analyzed and studied by paleontologists from the Department of Earth Sciences of the University of Pisa, in collaboration with those from GAMPS of Scandicci. Among the finds, numerous pectinid bivalves, such as Gigantopecten rotundatus, were identified, as well as oysters, gastropods, balanid crustaceans, and even sea urchins belonging to the species Spatangus subconicus, Ova karreri, and Clypeaster lovisatoi. Among other vertebrates found were sharks, including Cosmopolitodus hastalis, dolphins, dugongs of the species Metaxitherium medium, bony fish, and sea turtles.

The Ponsano Sandstones have been the subject of study since 1959, but they continue to reveal precious details about a world that has now disappeared. When these testimonies of the past are recounted with the careful and competent gaze of the scientist, they become a collective heritage of knowledge.