LATE PALAEOZOIC PLANTS OF SARDINIA: PALEOGEOGRAPHICAL AND PALAEOECOLOGICAL IMPLICATIONS

The study of the newly collected material and stored material coming from three different localities of Sardinia have been carried out for reaching the goals of this thesis. The oldest one comes from the San Giorgio locality, near Iglesias. The second one comes from Montarbu, and the third one comes from Perdasdefogu, central Sardinia. The last assemblage has been studied to obtain thin section from silicified rocks, unsuccessfully. The systematic study of the Moscovian flora of San Giorgio lets to highlight that the composition of this older flora is different from the younger Montarbu assemblage and reflects a late Moscovian wetland vegetation with a dominant sphenophytes-based flora. The Montarbu flora is composed of 24 taxa belonging to 18 genera with the abundance of mesophytic and xerophytic elements. Here, the conifers and cordaitanthaleans are dominant. The pteridosperms are common, and the most diversified in quantity of taxa, while ferns and rare sphenophytes are present as well. The assemblage reflects probably a very late Ghzelian age, because of the presence of typical taxa of “Stephanian affinity” and the abundance of Acitheca, peltasperms and conifers, much more meso-xerophytic. After the comparison between the Montarbu flora with those palaeogeographical close, it must be highlighted the strong similarity of the former with that of Igornay, in France. This value mirrors close paleogeographical condition that facilitates the presence of a similar set of vegetation. The similarity is also high with the less close Weissig Basin (Germany). It is assumable that during these times there were no (or weak) geographical barriers between the two floras. The similarity is also high with the floras of the Czech basins. Furthermore, the study of the two floras would also confirm the change of vegetation across the late Palaeozoic, as already seen in the various section of the same palaeolatitude and as evidenced in the regional palynological spectra.