Palinostratigrafia in sedimenti marini del Pliocene della Sicilia e considerazioni paleoclimatiche

Bertoldi, Remo

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 78 (1985) no. 4, pp. 157-164

Résumé

Pollen analyses reported here concern the well known lithological marine Pliocene sections of Capo Rossello and Monte San Nicola, both located in southern Sicily. A number of samples were investigated, but only those pertaining to the laminated anoxic type sediments ("tripoli" of Italian authors) turned out to be rich enough in pollen grains to obtain short sequences of palynological records. In particular pollen diagrams were obtained for three Pliocene intervals well spaced in time. These intervals had previously been dated by calcareous plankton biostratigraphy and assigned to planktonic foraminiferal zones M PL 2 (Early Pliocene), M PL 5 (Late Pliocene) and M PL 6 (terminal Late Pliocene). This palynological record, although discontinuous, nevertheless provides rather significant data on the floristic-vegetational and climatic evolution of the Southern Mediterranean Pliocene. At the top of the Globorotalia margaritae zone (M PL 2) the pollen grains of Pinaceae (Pinus in particular) are predominant. The deciduous forest components are quantitatively poor, while somewhat high frequencies show the non-arboreal pollen (NAP) associations. This palynofloral assemblage suggests a warm-temperate climate, but not humid conditions. Shortly after the appearance of Globigerinoides elongatus (M PL 5), the palynological sequential records are characterized by a decrease in Pinaceae and by an increase both in deciduous warm-loving and xerofitic taxa, with high values of NAP. This change is interpreted as indicating decreased moisture and gradually more xeric conditions. The Late Pliocene pollen spectra (Globorotalia inflata zone p.p.) (M PL 6) evidence sharp vegetational changes related to climatic fluctuations. A preliminary comparison between these first South Mediterranean data and the Northwestern Mediterranean pollen zones of Suc (1982) is carried out, despite clear differences in the qualitative and quantitative floristic records.