Palynology of the late Miocene Oreopithecus-bearing lignite from Baccinello, Italy

Abstract

This paper presents the results of an analysis of pollen and spores in 7 lignite samples from the vertebrate-bearing V1 lignite at Baccinello, Italy. The aim of the study is to reconstruct the vegetation associated with the vertebrate fauna, and to integrate this evidence with data from geological, paleontological and paleobotanical research in order to provide an improved understanding of the paleoenvironmental context. The V1 lignite, consisting of a 3 m seam near the base of the local geological sequence, is late Miocene (Tortonian) in age. It is dated at 8.5–9.0 Ma (European Mammal Zone MN 12) based on faunal correlations and on radiometric age determinations of an overlying tuffaceous layer. The fossil fauna comprises a small number of species, many of which are unique to the coal deposits of Tuscany, including the controversial hominoid, Oreopithecus bambolii. The high level of endemism, low taxonomic diversity, preponderance of ruminants, tendency for gigantism among some of the micromammals, and absence of cursorial carnivores, all point to an insular environment. Evidence from structural geology confirms that a tectonically unstable island arc bordered the eastern side of the Tyrrhenian Sea during the late Miocene. By a combination of island sweepstake events and ephemeral land connections, intermittent migrations of mammals from continental Europe and Africa led to the development of a unique fauna on islands of the northern Tethys Sea. The reconstructed vegetation is of lowland mixed mesophytic forest. The community of broad-leaved deciduous angiospermous and evergreen gymnospermous trees contained a rich understory of small trees and shrubs and an herbaceous ground cover. The abundance of aquatic seed plants and algae, as well as the preponderance of ferns and arboreal taxa that commonly grow on moist substrates, suggest that the lowland areas were poorly drained. Upland or montane habitats appear to have been present, but were located at some distance from the depositional basin. The rarity of grasses and chenopods indicates that extensive tracts of open country were of limited occurrence. The closest modern analogue to the vegetation is the mixed mesophytic forest of the Yangtze River Valley of east central China. It seems reasonable to infer that comparable warm temperate to subtropical conditions with high precipitation, especially in the summer months, characterized the late Miocene climate at Baccinello.