Palaeoenvironmental analysis of the Messinian macrofossil floras of Tossignano and Monte Tondo (Vena del Gesso Basin, Romagna Apennines, Northern Italy)
Abstrakt
Fossil leaves of Messinian age (ca. 5.7 Ma) from two sites of the Vena del Gesso Fm. (Monte Tondo and Tossignano, Ravenna and Bologna provinces, Italy) were studied morphologically to assess the taxonomic composition of the assemblages and carry out a palaeoenvironmental analysis. The flora of Tossignano so far comprises 41 vascular plant taxa with 8 conifers and 33 angiosperms (30 dicots and 3 monocots).
In the plant material from Monte Tondo 74 vascular plant taxa were recognized, with 11 conifers and 63 angiosperms (59 dicots, 3 monocots, 1 plant incertae sedis). Several fossil species well known in the Miocene of central Europe and Italy were detected.
The most frequent being Taxodium dubium, Pinus cf. rigios, Daphnogene polymorpha, Laurophyllum sp. 1 and 2, Platanus leucophylla, Quercus pseudocastanea, Quercus roburoides, Fagus gussonii, cf. Ailanthus pythii, Leguminosae gen. et sp. indet. 1.
The general palaeovegetation pattern of the Monte Tondo and Tossignano plant assemblages correspond to the vegetation transect of the Evaporitic Messinian with swamp, riparian vegetation, and zonal ""subtropical humid forest"". The results of IPR vegetation analysis for the ""subtropical humid forest"" zone indicate a transitional (ecotone) vegetation type between ""Broad-leaved Evergreen Forest"" and ""Mixed Mesophytic Forest"".
The Coexistence Approach estimates that both floras existed under comparable climatic conditions, with MAT 14-16.2 oC for Tossignano and 16-16.5 oC for Monte Tondo. This is warmer than the estimates derived from the Leaf Margin Analysis (MAT 13.8 oC and 14.3 oC) and Climate Leaf Analysis Multivariate Program (MAT 13.2 oC and 12.0 oC), and present day conditions in the Mediterranean Zone (MAT around 13.5 oC).