Ricerc@Sapienza

Diatomite deposits in the Sabatini Volcanic District (central Italy) represent valuable archives to investigate both Middle Pleistocene vegetation dynamics and geochemistry of proximal products of volcanic eruptions, which provide crucial geochronological markers for a large region of Southern Europe. We present a new pollen record from a diatomite deposit at Rignano Flaminio, attributed to MIS 13 based on two major eruptive events from Monti Sabatini: the Grottarossa Pyroclastic Sequence (513 ± 3 ka) and the Fall A unit (499 ± 3 ka). We also add insights into the geochemical and mineralogical composition of the proximal deposits of the Fall A tephra, whose products are found in several sites of the central Mediterranean. Our pollen record shows marked vegetation turnovers, reflecting changes in regional and global climate conditions, local environmental factors and ecological processes within refuge areas. The lower part of the record points to a forested environment dominated by both deciduous and evergreen broadleaved taxa, indicating wet and temperate climate conditions. This interval was punctuated by two phases of slight forest declines, where a general increase in Poaceae and Artemisia, coupled with the development of Ericaceae and evergreen Quercus communities, suggests the establishment of mediterranean-type climatic conditions with increased aridity. The upper part of the sequence shows the development of Abies and Pinus woodlands, reflecting a change towards cooler and possibly wetter climate. The pollen richness, accompanied by a fossil leaf of Laurus, confirms the role of the Sabatini Volcanic District as a Pleistocene biodiversity hot-spot and refuge area for many trees.