Access to Chão de Pias coming from:

- Porto de Mós (± 8.8 km) - N362 to Serro Ventoso and Pebada street.

- Alcanena (± 25 km) N361 to Cortiçal. There take 25 de Abril street and Principal street.

The place does not have access, so it should be observed from afar.

GPS: 39.563728, -8.805549

This geologic section, a rhythmic alternation of marl and argillaceous limestone, is the stratotype for the lithostratigraphic unit known as "Formation of Barranco de Zambujal" from the base of the Middle Jurassic. It is also a very important biostratigraphic reference section to characterize the Lower to Middle Jurassic of the Lusitanian Basin, because it allowed to safely recognize various biozones of ammonites of the Upper Toarcian (Biozone Aalensis) to the Lower Bajocian (Biozone Sauzei), including those defining the limits Toarcian-Aalenian and Aalenian-Bajocian.

The series Barranco de Zambujal was deposited in an external marine environment, relatively deep, possessing, besides the ammonite’s fauna, an important paleontological content consisting of belemnites, brachiopods, lamellibranchs and ichnofossils.

Ammonite or ammonoid - Marine animals with a shell, similar to nautiloids, which appeared in Lower Devonian, more or less 400 million years ago (Ma), having evolved rapidly in the following 340 Ma, being quite abundant and having a wide distribution, suddenly disappearing at the end of the Cretaceous. They are, therefore, excellent stratigraphic fossils for the Mesozoic, allowing dating rocks with an error of less than 1 Ma.

Belemnite – from the Greek belmnon meaning “arrow, dart” and eidos  shape, meaning animal with an arrow form. Extinct group of cephalopods, currently represented by cuttlefish and squid.

Biozone – layer or set of layers characterized by the existence of one or more species of fossil that give it its name. It is the base unit of the biostratigraphic zonation.

Brachiopod – from the Latin brachio meaning arm and poda foot. Marine invertebrate (shellfish) with two different shells and two tentacles used to filter nutrients from the water.

Ichnofossil or ichnite – from the Greek iknos meaning trace. In fact, it is a fossil trace of organism’s biological activity that existed in the past (e.g. footprints, travel tracks, droppings, eggs and fossilized teeth marks are examples of ichnites).

Jurassic - geological period in which the dinosaurs dominated and the development of vegetation was abundant. It lasted about 54 million years, roughly between 208 to 144 million years ago.

Lamellibranch - the same as bivalve, mollusc animal with two shells feeding on nutrients by filtering the water, e.g. oyster.

Marl - sedimentary rock that has a carbonate and a clay component in more or less equal parts.

Stratigraphy - study of sedimentary rocks and associated geological event.

Stratotype - sequence of sedimentary rocks used as a stage reference. Its name is generally formed by adding "ian" to the name of the region or locality where it was set. E.g. Toarcian comes from Thouars region in western France, which in Latin was called Toarcium.

International Chronostratigraphic chart