Verolino A, A D’Agostino, G Di Marco, S Marvelli, A D. Switzer, A Canini, A Gismondi

Geological Journal

Fossil pollen has long been used for paleoenvironmental and paleoclimatic reconstructions. However, to date, pollen extraction has primarily focused on unconsolidated sedimentary successions within enclosed basins of limited spatial extent, such as lacustrine basins. In this work, we successfully extracted ancient pollen from consolidated volcanic deposits, particularly pyroclastic density current (PDC) deposits, which are usually emplaced on a large spatial and temporal scale. This exploratory study aims to test the efficacy and applicability of standardised pollen extraction methodologies on consolidated volcanic material. As a case study, we examined units from the Colli Albani Volcano, Italy, active during the Quaternary; specifically, the Trigoria—Tor de’ Cenci unit, dating back approximately 550,000 years, and the more recent Peperino Albano unit, dating to about 36,000 years ago. This selection allowed us to evaluate pollen preservation across two stratigraphically distinct and well-studied units, each corresponding to different climatic periods. Furthermore, our findings shed light on pollen entrainment mechanisms within pyroclastic density currents during transport, from the source to the emplacement site. We inferred that both investigated PDCs were characterised by pollen entrainment through ground uprooting and marginal air incorporation. Our results can be validated both in terms of expected pollen type variability with respect to the location of the deposit from the source (e.g., higher pollen variability observed at the distal TTC unit) and in respect to the expected vegetation dynamics for the respective periods and areas investigated, with the latter partially verified through comparison with pollen studies at nearby locations. This work, though not exhaustive and not meant to be used for paleoenvironmental and paleoclimatic reconstructions, proves the efficacy of pollen extraction from consolidated PDCs through standard methods, and its applicability for more comprehensive studies, by incorporating pollen data from loose sedimentary successions and from nearby volcanic units.