Alba territory Messinano geological horizon is particularly important for the high presence of fossils.

The collision between African and Eurasian Continental lithospheric plate caused some rises of the mediterranean area, which caused the reccurent isolation of protomediterranean sea from Ocean waters starting from 5.96 mya. During this period the basin underwent severe evaporation episodes because of subtropical-like hot temperatures. The lack of over-washing of colder ocean waters and the scarce uptake of continental fresh water caused the lowering of sea level.

This situation leaded to a fenomenon called “Salinity Crisis”, i.e an high concentration of sea water dissolved salts that progressively caused carbonates, calcium sulphates and sodium chloride precipitation.

In particular, Alba territory sea basin decreased by 80% in volume, causing calcium sulphate (gypsum) precipitation.

Lack of oxygen (anoxic environment) and the absence of biodegraders organisms promoted fossilization and an excellent preservation of what fell down in the water, including very fragile structures such as leaves, flowers, fruits, insects, larvae and plume.

Is in that period that there was the constitution of groups of “Gessoso-solfifera Formations”, that shows a fair purity in a thickness of 100 meters.

From these formations gypsum has been extracted until recent past; gypsum was especially used as a component of “scagliola”, which is wide employed in construction industry.

Facies a congerie

Brackish water littoral lagoons were forming at the edges of sea basin; here lived few shellfishes species adapted to the particular physical and chemical conditions. Those lagoon environments bring to the so called “Facies a Congerie”, composed by sediments that in some places mark the maximum passage for the later Pliocene clays.