The streams of Cherasco

In the bed of Ruisseau Crosio, a tributary on the right bank of the Stura de Demonte river, west of the town of Cherasco, the Lugagnano Clays emerge, also known as Clear Blue Clays. These are part of the sedimentary succession that marks the passage of the Miocene (Marls of Sant'Agata, Fossils of the Tortonian, Evaporitic Messinian of the Gesso Vein, where we witnessed a salinity crisis in the Mediterranean basin, with a logical drop in sea level, until reaching conditions of emersion with the continental deposits of the Cassano Spinola Conglomerate). In the Pliocene, with the return of deep sea conditions, the Lugagnano Clays are deposited, followed by the Sables d'Asti (coastal deposits). The final filling of the marine basin is carried out with fluvial and deltaic contributions from Villafranchien. Here are the events which took place in the Cherasco area between -11 and -2 million years ago. In this time interval the clays of Crosio de Cherasco Creek are dated -5 million years old thanks to the fossils they contain.

Scientific concept

These are light blue clays, inside which we find large mollusks with small white shells, very fragile; a few years ago, the most important paleontological discovery was that of the fossils of two magnificent starfish (of type astropects cf. irregularis pentacanthus - Common comb star completely devoid of prickles on the supramarginal plates, present in the Mediterranean). The study of micro-fossils, Foraminifera, both benthic (which live on the seabed) and planktonic (which live and move in the water section), and their relative abundance, provide scientific data. essential: they are the ones that allow us to date the sediment to - 5 million years (Zanclean stage of the Lower Pliocene) and to analyze a marine ecosystem that developed at a depth of about 100 meters. The light blue color of the clays indicates a quiet environment and low oxygenation of the water.

Other links 22 sites - The Cherasco streams came into being as a result of the great geomorphological phenomenon known as 'Cattura del Tanaro' (Capture of the Tanaro), which changed the geography of most of the alpine rivers of southern Piedmont during the last ice age. The Tanaro, which previously joined the Po around Carmagnola, was either captured directly or via a stream that cleared its way following the Messinian gypsum outcrops in the Alba valley. The sudden change in altitude of this new route favored a rapid erosion of the sediments of the Piedmont Tertiary Basin caused by the rivers, also involving the area known as Rocche du Roero, the Stura river and its tributaries. Thus was born the promontory of Cherasco and the plateau located between Bra, Fossano and Cuneo: the deep groove exposed to broad daylight the buried sediments which today tell the story of the last millions of years of this corner of the Plain of Po.

Landscape link news

The erosion of the canyons carved by the Cherasco streams continually expose new fossils, which deserve to be watched and reported. The name Rio Crosio derives from the local dialect “encreus”, which means deep. It is indeed a canyon with vertical walls, where nature still reigns in the wild, with resurgences and more than 700 species of flowers and plants both alpine (cold type) and Mediterranean (from hot type) according to their exposure; on the banks of the canyon, one can listen to birdsong, while fleeting animals hidehave as you pass. All the plant and animal life develops around the stream, following a rule as old as the world. Thus, before these delicate ecosystems permanently disappear, man must learn to protect and respect these fragile environments, including the catchment structures which are upstream and which divert or discharge water into the hydrographic network of streams.


The starfish from the Crosio de Cherasco stream were discovered in 2012 by a local child, during a walk with her father on the path which has now been redeveloped.       

This curious and meticulous girl, named Ginevra Grisotto, was then following her second year of college.

After the discovery and its announcement to the city museum, the Archaeological Department entrusted the mission of research and study of the fossils contained in the sediments to paleontologists Giovanni Repetto, from the “Federico Eusebio” Municipal Museum of Alba, and Erica Bicchi of the Environmental Sciences Pole, Esaip Group, of Saint Barthélémy d'Anjou in France. Today the two type starfish astropects are kept at the Segre Museum in Cherasco. The exceptional character of this discovery lies in the fact that only two others are known in the territory of Alba and Bra:  Astropecten bispinosus - Bristly comb star (Otto, 1823), observed and described by Federico Sacco (1893) for the Pliocene of Bra, and a fossil copy, unfortunately lacking in notable details, illustrated by Oreste Cavallo and other authors (1986), found in the Tortonien des marls in Alba.