Paleozoic Era: Ordovician


The oldest sedimentary – and fossiliferous – rocks of the entire the Alpine chain date back to the Ordovician. These are not generally common, and are about 460 million years old. These are greyish-green and yellowish siltites and known as the Uqua Formation. The environment in which they were formed was that of a shallow sea, in a temperate-cold climate. They emerge especially in the area of ​​Paularo (casera Valbertad), a site where they are very fossiliferous. The Ordovician rocks rest on a base consisting of metamorphic rocks of uncertain age, an example being  the Fleons Formation.
Typical fossils of the Ordovician include bryozoans, brachiopods, cystoids and trilobites.