Palynological approach in upper Quaternary terrestrial carbonates of central Italy: Anything but a mission impossible

A palynological survey has been carried out on two late Quaternary travertine s.l. deposits of central Italy at Serre di Rapolano and Bagnoli (Tuscany region). The principal aim was to improve the understanding of factors that affect the accumulation and preservation of pollen grains in thermal (i.e. travertine) and ambient temperature (i.e. calcareous tufa) terrestrial carbonates. For this purpose, 52 526 pollen grains belonging to 118 pollen taxa from local to extra-regional sources were analysed in 200 samples from different travertine and calcareous tufa lithofacies. Of these, 97 samples, generally from thermal travertines, were barren in palynomorphs. By contrast, pollen grains in the remaining samples were well-preserved and did not show differential preservation features. These observations suggest that the pH of the solutions from which travertine or tufa precipitate is not a limiting factor in causing corrosion and/or destruction of pollen grains. Rather, the barrenness recorded in many samples appears to reflect a paucity of pollen rather than post-depositional destruction. Results suggest that the depositional energy of the environment during the deposition of travertine plays an important role in controlling pollen concentration, as verified in both depressions (lower energy to higher pollen concentration) and slopes (higher energy to lower pollen concentration), respectively. Analysis of pollen data suggests that relatively high depositional temperatures and rates of carbonate deposition are also major limiting factors for efficient accumulation of pollen grains. Results of this study reveal that understanding pollen taphonomy processes in travertine and calcareous tufa is critical to developing accurate palaeoenvironmental and palaeoclimatic reconstructions.