New insights on the sedimentological and biostratigraphic record of the Upper Cretaceous of the Salento Peninsula (Apulia, Southern Italy): collecting data from an abandoned quarry near Manduria

The analysis of vertebrate material from the Salento Peninsula (Italy), currently stored at the Museum of Paleontology of the University of Rome ‘Sapienza’ and the Natural History Museum in Verona, led us to conduct a preliminary field survey and prospection in order to localize suitable outcrops for paleontological excavations. As a result, new stratigraphic and sedimentological features of the Cretaceous limestones of the Apulian Carbonate Platform are here reported. The attention was focused on the northern sector of the Salento Peninsula, and in particular on an abandoned quarry about 2 km NE of Manduria (Taranto, Italy). About 8 meters of Upper Cretaceous ‘Plattenkalke’-type deposits referable to the Calcare di Altamura Fm., showing interesting paleontological and geological aspects, are here exposed. A high-resolution litho-biostratigraphical study of the succession was performed at a mm-scale in order to reconstruct the paleoenvironment setting of the area. From a stratigraphic and sedimentological point of view, the lithotypes outcropping in the quarry are dominated by the cyclic alternation of: i) mm- to cm-thick, dome-shaped, cyanoalgal laminites, sometimes cross-cut by mud-cracks; ii) ‘fenestral’ horizons made of prismatic-to-discoidal voids, in some cases larger than 1 cm, related to dissolution of evaporitic salts (mainly sodium chloride); iii) wedge-shaped pedogenetic horizons (terre rosse) and paleokarst structures, sometimes associated with syn-sedimentary tectonics. From a paleontological point of view, a unique and well-preserved thanatocoenosis characterizes the studied succession. The macrofauna is strictly oligotypic and consists of fish-remains, coprolites, regular sea urchins and few specimens of Chondrodonta sp., while the microfauna is totally absent. The main feature is represented by the kind of preservation of the echinoids and their spines. In fact, echinoids are preserved as “ghosts”, with the original high-Mg calcitic test completely leached. The moulds are partially filled by yellow-orange silt and clay, referable to incipient paleokarst features, or by crusts of microcrystalline calcite. Furthermore, a large number of isolated radioli were found, while no echinoid tests with articulated spines were recovered. The facies analysis of the “vuggy” and laminated limestones suggests a saline and dry, supratidal mudflat-type setting as depositional environment. Hypersaline conditions are highlighted by salt-rich levels, while periodical and ephemeral flooding of normal-salinity seawater allowed the colonization of the sea floor by benthic organisms (mainly echinoids), and occupancy by fishes. Extreme conditions of the depositional setting are marked by the total lack of the microfauna. Finally, the occurrence of occasional wet phases also led to the development of soils and karstic phenomena.