Malacofauna pliocenica di Castellengo (Biellese, Italia NW)

- [Marin molluscs and continental vegetal remains pliocene assemblage of Castellengo (Biella, Piedmont, NW Italy)] An assemblage from a Pliocene sandy level of Castellengo, cropping out on the left bank of the Torrente Cervo, was studied in a 10 dm3 bulk sample. 140 molluscs taxa were recognized. Seven of them are reported for the first time from the Biella area (Candelo, Cossato, Masserano). The assemblage of Castellengo is composed by two main groups of fossils with different environmental significance. The first one mostly consists of infaunal suspension feeders dwelling in sandy-muddy sediments of the infralittorale zone, mainly referable to the SFBC palaeobiocoenoses. The second group includes molluscs living on a deeper bottom and in more heterogeneous sediments, mostly referable to the VTC and DC palaeobiocoenoses and possibly transported to shallower depths by bottom currents. The associations was named "Nucula jeffreysi and Turritella tricarinata Fossil Assemblage" from the two most common taxa. A comparison with the other assemblages of the same NE Piedmont area was made. Biostratigraphic data and correlation with the other Pliocene assemblages of the Biella outcrops allow to date the Castellengo malacofauna to time interval included between late Zanclean and early Piacenzian, before the 3 My cooling event.