Relationships between the Pesciara di Bolca and the Monte Postale Fossil-Lagerstätten (Lessini Mts., northern Italy)

Very close (about 300 m) to the world-famous Pesciara di Bolca Fossil-Lagerstätte, the Monte Postale is the only locality where it is possible to follow a more or less complete sedimentary succession. Despite their closeness, the geological and stratigraphical relationships between the Pesciara and the Monte Postale are still poorly known. This is mainly due to the widespread volcanic and volcanoclastic deposits that, together with tectonic movements of different ages, extensively dismembered and displaced the sedimentary rocks. Therefore, there is no continuity between the limestone of the Pesciara succession and the similar rocks of the Monte Postale, on the opposite side of the valley.At present, the stratigraphy of the Monte Postale succession is still founded on the sketch and description of Fabiani (1914). More recently, Massari & Sorbini (1975) described only a part, about 30 m thick, of the Monte Postale succession.We recently re-examined the whole succession, measuring a composite stratigraphic section made up by two sections (lower and upper) separated by a fault (the Monte Postale fault). The preliminary results of the study of the samples collected revealed that the upper section, bearing quite rich Alveolina assemblages could be dated to the SBZ 11 biozone, i.e. Middle Cuisian (Ypresian). The upper section contains laminated micritic limestone with fish and plants, which are therefore contemporary to the similar limestone of the Pesciara section.The characters of the Monte Postale laminated limestone (MPLL) are in some way different from that of the Pesciara (PLL), because the MPLL bear often bad-preserved fishes (Massimo Cerato, pers. comm.) as compared with the ones coming from the PLL. Moreover, the Monte Postale succession includes a significant thickness of “normal” limestone, very rich in benthonic fossils (especially Alveolina), witnessing the prolonged conditions of normally oxygenated sea bottom, with some intervals of oxygen depletion marked by the MPLL.In the Pesciara section, all the larger foraminifers and other benthic fossils were transported and redeposited in an anoxic environment with terrigenous inputs mainly due to aeolian transport (Schwark et al., 2009).According to these data, we can provisionally conclude that the Monte Postale succession represents a palaeoenvironment more open to marine circulation and consequently better oxygenated than the Pesciara “basin”. More detailed analyses are required to better precise the palaeoenvironmental evolution in the Monte Postale succession.ReferencesFabiani, R. 1914: La serie stratigrafica del Monte Bolca e dei suoi dintorni. Memorie dell’Istituto di Geologia della Regia Università di Padova 2 [1913], 223-235.Massari, F. & Sorbini, L. 1975: Aspects sédimentologiques des couches à poissons de l’Éocène de Bolca (Vérone – Nord Italie). IX Congres International de Sedimentologie, Nice, 55-61.Schwark, L., Ferretti, A., Papazzoni, C.A. & Trevisani, E. 2009: Organic geochemistry and paleoenvironment of the Early Eocene “Pesciara di Bolca” Konservat-Lagerstätte, Italy. Palaeogeography, Palaeoclimatology, Palaeoecology 273 (3-4), 272-285.