Romanterra – marine strata and fossils

 

Along the riverbed of the Caffaro river, near the Romanterra bridge in Bagolino, a range of layers from the Middle Triassic period can be seen in an exemplary way, including the Price Limestone, the Buchenstein Formation and the Wengen Formation, in which some fossils and traces of animals typical of a relatively deep sea. The marine fossils of Romanterra include remains of ammonoids and bivalve shells useful in establishing the age of the various layers. In addition, vertebrate remains can be found, such as scattered bones of ichthyosaurs (aquatic reptiles) and fish. Other marine fossils, such as tiny remains of skeletons of radiolarians (unicellular organisms) and conodonts (chewing apparatuses of small invertebrates), are visible only under the microscope.

 

The ammonoids, the dams, but also the traces left by organisms on the seabed are typical of a marine environment whose depth could be around 100-200 meters. Remains of plants are present as carbonaceous fragments and document the existence of nearby emerged areas (islands or mainland) covered by vegetation.

 

“The golden nail” for the Ladin plan

 

In the modern international geological scale, every limit between the subdivisions of the different periods must be defined with a single world reference point. This point is called GSSP (Global Stratigraphic Section and Point) or briefly “golden spike” (golden nail) which symbolically indicates the exact position of the limit.

 

In 2005, the Romanterra site was chosen as a reference point for the boundary between the ANISICO and LADINICO planes for the representativeness of the outcrop, for its fossils and for the accuracy of the dating of the strata.

 

For the Triassic period the names Anisico and Ladinico had actually already been introduced in the second half of the 1800s by Austrian geologists. The expression Anisico comes from the name of the Austrian river Enns (lat. Anisius) south-east of Salzburg, while the Ladinic took its name from the Ladin-speaking population in the Dolomites, areas where the rocks of the Triassic are widespread.