Abstract

A new calcareous-dolomitic horizon of a platy-dolomite type (sensu Bernier, 1994), containing the remains of a Cenomanian continental palaeoflora, is reported. The platy-dolomite crops out in the Mount Chianello carbonate ridge (sheet tav. I.G.M. 1:25.000, 198 II S.W. - Castel San Lorenzo), dominating the village of Magliano Vetere (SA). This ridge is a deformed part of a Mesozoic-Cenozoic platform ("campano-lucana" platform in D'Argenio et alii, 1973; "apenninic" platform in Mostardini & Merlini, 1986). A 200 m thick interval of the sequence has been sampled in order to date this platy dolomite. On the basis of facies, it has been divided into four intervals which are, from bottom to top: a) 50 m stromatolitic dolomite and limestones below the "platy dolomite", showing the sedimentological features of a restricted lagoonal environment in an inner carbonate platform. Among the microfossils, Sellialveolina viallii Colangolo, Nezzazata simplex Omara, Pseudolituonella reicheli Marie, Biplanata peneropliformis Hamaoui & Saint-Marc and Pseudorhapydionina dubia (De Castro) are present. This fossil assemblage indicates an age ranging from the base of the Cenomanian up to the middle Cenomanian (De Castro, 1991). b) 70 m thin-bedded dolomite and dolomitic limestones of which the typical platy dolomite facies constitutes 40 m in which sets of millimetre-scale laminae are frequently present and often contain terrestrial floral remains on the laminae surfaces. The fossiliferous horizon is ascribed to the middle-upper Cenomanian by the presence of Nezzazata simplex Omara, Biconcava bentori Hamaoui & Saint-Marc, Biplanata peneropliformis Hamaoui & Saint-Marc, Chrysalidina gradata D'Orbigny, Pseudorhapydionina dubia (De Castro), Pseudorhapydionina laurinensis (De Castro). The sedimentological features of the platy-dolomite and fossil flora content suggest deposition in a tidal flat under upper intertidal-supratidal conditions and, in particular, in an algal-marsh environment often exposed to dessication and storms, located close to a coastal area with primeval Angiosperms and Conifers. The first palaeontological studies on this continental flora, allow us to ascribe some fossils to Sapindopsis sp.. c) 42 m limestones and bioturbated dolomite which mark a drastic change in the environmental and sedimentological conditions on the carbonate platform, with heavily bioturbated biodetrital material (mainly fragments of Rudists), often in massive layers, proving a swift transition to deeper open marine conditions. In particular, the first 18 metres of this interval have many traces of Thalassinoid bioturbation. The tracks and burrows give an unmistakable appearance to the rocks and make this an important marker horizon in the whole ridge of Mount Chianello-Mount Vesole. Because of the presence in thin section of Dicyclina sp., Cisalveolina fraasi (Gumbel) and Pseudorhipydionina casertana (De Castro), a late Cenomanian age is assigned to this interval. d) 43 m of limestones and dolomite. The sedimentological features indicate an open carbonate platform environment often with coarse biodetrital elements and, in the upper part, a tendency to the emersion. This interval has been assigned to the Turonian by the presence of Murgeina apula (Luperto-Sinni), Biconcava bentori Hamaoui & Saint-Marc and small Moncharmontia apenninica (De Castro).

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