Abstract

An enigmatic deposit at Pavone d’Alessandria provided, at the end of the 19th century, about one hundred plant macrofossils, considered to be Oligocene in age. That material is no longer available, but a few animal (an insect and a fish) and plant remains have recently been recovered from this locality. A single remnant of Aphanius crassicaudus is considered relevant, in combination with a recent assessment of the geology in the studied area, to propose a Messinian age for the deposit. The taxonomic composition of the 19th century plant assemblage, only documented by sketchy drawings, is difficult to re-interpret, but its possible relationship with Messinian plant assemblages studied in the last 30 years is discussed in the light of recent observations. A few plant taxa that can be recognized on the basis of elementary morphological traits, e.g., Fagus gussonii, support a Messinian rather than Oligocene age.

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Abstract

The late Early Pleistocene was the last time of equable climate in northern Central Italy, reflected in its large mammal fauna and numerous palynological records. Reliably dated leaf fossils from this time are rare, but provide crucial information on local and regional vegetation, biogeographic relationships, and species turnover coinciding with the assembly of modern forest biomes. Here we investigated a rich assemblage of leaf and fruit impressions (63 fossil-taxa) from the Oriolo quarry, Faenza (Ravenna), dated to the latest Calabrian, preserved in transgressive coastal deposits. The fossil assemblage represents riparian vegetation and xeric alluvial habitats in the lowlands and forest vegetation above the alluvial plain. Forest-building trees were deciduous, but comprised several taxa characteristic of open scrubland or forest edges. The composition of the flora reflects a dynamic process of assembling modern forest biomes in western Eurasia. While most taxa correspond to modern submediterranean and temperate woody species, some others represent late occurrences of taxa today confined to refugia outside Italy (Parrotia, Gleditsia, Pterocarya), and a few are Miocene/Pliocene relics indicating final floristic links with East Asia (Japan) and/or North America (Tsuga cf. chiarugii, Carya cf. minor) and Pleistocene endemism in Italy (Berberis auriolensis, Acer aemilianum).

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In the Piedmont Basin (PB), one of the northernmost Mediterranean basins recording the Messinian Salinity Crisis (MSC), pollen and plant macroremains (leaves, fruits and seeds) were studied in four sedimentary sections of the post-evaporitic interval (5.6–5.33 Ma). The joint palaeobotanical investigations of the two datasets allowed the reconstruction of a floristic assemblage which consists of 133 taxa (95 woody and 38 non-woody taxa). The lowland/coastal vegetation reconstructed by integrating macro- and microfossil data exhibits several analogies with existing “types/formations” of South-Southeast Asia, whereas taxa occurring solely in the pollen record suggest the existence of altitudinal forests with conifers and a few angiosperms. We suggest that the generalized type of lowland, zonal palaeovegetation in the post-evaporitic Messinian of the PB was of no-analog type, but most similar to either “mixed mesophytic forests” or “broad-leaved evergreen forests”, which indicates a Köppen-Trewartha subtropical palaeoclimate.

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The first results of a multidisciplinary study on the Messinian evaporitic interval of the Govone section (northwestern Italy), subdivided into several sedimentary cycles, are reported here. Primary sulphate evaporites and intercalated shaly deposits, which formed during the Messinian Salinity Crisis, contain well-preserved and taxonomically determinable terrestrial plant remains. Palynomorphs are present continuously all along the analysed succession and among them, pollen is especially abundant and diverse. Additionally, a few fragments of silicified wood (which are rare in the studied area) occurred in layers rich in phytodebris, but their analysis showed poor preservation of anatomy. Carpological remains are not abundant and are strongly altered by diagenesis. Compressed conifer shoots and angiosperm leaves are well-preserved in several layers, one of which yielded a particularly diverse assemblage. The various plant records have been integrated to obtain an initial general idea on the floristic composition of the assemblages and the palaeoenvironment. We hypothesize that a subtropical humid forest may have surrounded the basin, not only during the deposition of shale deposits, but also during the formation of gypsum, generally considered a product of arid climate. Despite the low-resolution sampling strategy for macrofossils, the identification of several relevant plant taxa (Engelhardia orsbergensis, Eurya stigmosa, Symplocos casparyi, Taiwania sp.), seems to indicate that the Govone section could provide an interesting glimpse into the composition of the palaeoflora of northern Italy during the deposition of the Messinian evaporites.

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