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The Stirone and Piacenzian Park, between the Piacenza and Parma provinces, yields a very rich paleontological heritage that makes it a true open air museum. Here, along the Arda riverbed, a torrent at the foothills of the medioeval town of Castell'Arquato, a succession of sands, clays and conglomerates rich with fossils that record the last two million years of the history of Emilian Apennine, Adriatic Sea and Po Valley crops out.

Walking along the riverbed we can observe in the strata that crop out along its argins the evolution of the early and middle Pleistocene paleoenvironments. A 200 m-thick marine succession deposited in the paleo-Adriatic Sea, in a tectonically active setting characterised by fore-stepping fan deltas, crops out in the lower part. This is given a Calabrian age (1,806-0,781 million years ago) thanks to the study of associations of molluscs, foraminifers and calcareous nannofossils. Rich and well-preserved shell beds are characterised by a rich diversity of bivalves, gastropods, scaphopods, brachiopods, corals, bryozoans, anellids, echinoderms, arthropoda and fishes, with rare findings of marine phanerogams belonging to the species Posidonia oceanica. bivalves and gastropods are often represented by Aequipecten spp., Glycymeris spp., Venus nux, Acanthocardia spp., Tellina spp., Naticarius spp. and Nassarius spp.

The composition of these shell beds has a paleoclimatic significance. The lack of tropical molluscs typical of the Pliocene and the presence of "boreal guests" like the bivalves Arctica islandica and Pseudamussium septemradiatum and the formainifers Hyalinea balthica and Neogloboquadrina pachyderma document in fact the climatic deterioration that has interested our emisphere between the Gelasian and the Calabrian, main signature of the lower Pleistocene. "Boreal guests" are those organisms that today live at high latitudes in the boreal emisphere, along the coasts of Iceland, Norway and North America, and that migrated in the Mediterranean through the Strait of Gibraltar after the climatic cooling that began during the Calabrian, at around 1,8 Million years ago.

The marine succession passe supward to continental sediments, at first conglomerates, than fluvial deposits with freshwater and terrestrial molluscs, together with leaves, seeds and trunks with roots still preserved in situ. Among the frequent vertebrate remains, the species Sus strozzii, Stephanorhinus hundsheimensis, Ursus dolinensis, Pseudodama farnetensis and others belonging to the genera Bison, Hippopotamus and Praemegaceros have been recognised. Up to more than 800 marine and continental species are today housed and exposed at the Geological and Paleontological Museum "Giuseppe Cortesi" at Castell'Arquato, a wonderful example of the paleontological wealth of the Arda torrent.

Further reading

Bona F. & Sala B. (2016). Villafranchian-Galerian mammal faunas transition in South-Western Europe. The case of the late Early Pleistocene mammal fauna of the Frantoio locality, Arda River (Castell’Arquato, Piacenza, Northern Italy). Geobios 49: 329-247.

Crippa G. & Raineri G. (2015). The genera Glycymeris, Aequipecten and Arctica, and associated mollusk fauna of the Lower Pleistocene Arda River section (Northern Italy). Rivista Italiana di Paleontologia e Stratigrafia 121: 61-101.

Crippa G., Angiolini L., Bottini C., Erba E., Felletti F., Frigerio C., Hennissen J.A.I., Leng M.J., Petrizzo M.R., Raffi I., Raineri G. & Stephenson M.H. (2016). Seasonality fluctuations recorded in fossil bivalves during the early Pleistocene: Implications for climate change. Palaeogeography, Palaeoclimatology, Palaeoecology 446: 234-251.

Dominici S. (2001). Taphonomy and paleoecology of shallow marine macrofossil assemblages in a collisional setting (late Pliocene–early Pleistocene, western Emilia, Italy). Palaios 16: 336–353.

Dominici S. (2004). Quantitative taphonomy in sandstones from an ancient fan delta system (Lower Pleistocene, Western Emilia, Italy). Palaios 19: 193–205.

Monegatti P., Raffi S., Roveri M. & Taviani M. (2001). One day trip in the outcrops of Castell’Arquato Plio–Pleistocene Basin: from the Badlands of Monte Giogo to the Stirone River. Paleobiogeography and Paleoecology 2001 International Conference, Excursion Guidebook, Università di Parma, 26 p.

Monesi E., Muttoni G., Scardia G., Felletti F., Bona F., Sala B., Tremolada F., Francou C. & Raineri G. (2016). Insights on the opening of the Galerian mammal migration pathway from magnetostratigraphy of the Pleistocene marine–continental transition in the Arda River section (northern Italy). Quaternary Research 86: 220-231.

On the web

Museo Geologico ‘G. Cortesi’, Castell’Arquato
Parco dello Stirone e del Piacenziano

Text by Gaia Crippa
Photographs by Gaia Crippa and Stefano Dominici

(partially in English)