The Ypresian succession of the Monte Postale and its relationship with the Pesciara di Bolca (Verona/Vicenza Provinces, Northern Italy)

The Eocene locality of the Monte Postale, together with the most famous Pesciara di Bolca, has been known from centuries for its exceptional fossil content of plants and fish (e.g. Sorbini, 1972). Curiously enough, the most recent description of the entire stratigraphic succession of the Monte Postale is due to Fabiani (1914). In 1975 Massari & Sorbini described only a part of this succession, approximately 30 meters thick. So, this succession has been recently re-examined to determine its age and palaeoenvironmental evolution. Several samples contain larger foraminiferal assemblages, especially Alveolina, but also Nummulites and “Orthophragminas”. Some of them show tests moderately abraded and sorted, suggesting a limited transport of the bioclasts. However, the greater part of the samples contains autochthonous assemblages, with no signs of substantial transport. The study of the Alveolina assemblages allowed us to determine the age of the levels sampled. The assemblages observed along the main part of the succession (approximately 80 m of thickness), including the levels bearing fish and plants, contain Alveolina cremae, A. aff. croatica, A. decastroi, A. distefanoi, A. levantina, A. rugosa, etc. This faunas allowed us to insert all these beds into the SBZ 11 biozone (Middle Cuisian, Ypresian). With these new data, we can correlate the Pesciara beds with those of the Monte Postale. They turned out to be contemporary, within the resolution power of the shallow benthic alveolina biozones. The main difference appears in the palaeoenvironmental context: • mostly of shallow water carbonate platform with normal oxygenation at the Monte Postale; • mostly of restricted anoxic “basin”, but with frequent storm events, at the Pesciara.Therefore, the levels bearing fish and plants of the Monte Postale are contemporary (within the limit of the resolution power of the shallow benthic biozones) to those of the Pesciara. Moreover, the palaeoenvironmental conditions were roughly the same in the two localities. The rather worst preservation of the fishes from the Monte Postale could suggest some differentiation. The Monte Postale succession, where the taphonomic processes acted more effectively, could testify a somewhat more “open” palaeoenvironment with respect to the Pesciara one.In conclusion, the detailed study of the Monte Postale succession turns out to be essential both to widen our knowledge of the palaeoenvironments of the Bolca area and to better understand the origin of the fossil fishes.References:Fabiani R. (1914) - La serie stratigrafica del Monte Bolca e dei suoi dintorni. Mem. Ist. Geol. R. Univ. Padova, 2 [1913]: 223-235.Massari F. & Sorbini L. (1975) - Aspects sédimentologiques des couches à poissons de l’Éocène de Bolca (Vérone – Nord Italie). IXe Congr. Int. Sedimentol., Nice: 55-61.Sorbini L. (1972) - I fossili di Bolca. Mus. Civ. St. Nat. Verona, 133 pp