Geochemical and mineralogical proxies from the Messinian mudrocks (Catanzaro Basin, southern Italy): Paleoweathering and paleoclimate evolution during the onset of the Messinian salinity Crisis

The bulk mineralogy and geochemistry of mudrock samples from a representative section of the Calcare di Base Formation outcropping in the Catanzaro Basin (Calabria) were studied using X-Ray Diffraction and X-Ray Fluorescence techniques. Phyllosilicates are the main mineralogical constituents followed by quartz, calcite, feldspar, hematite and gypsum in the lower part of the studied succession, whereas calcite is the main mineralogical component in the upper part. The geochemical composition reveals that SiO2, Fe2O3, Al2O3, CaO and MgO are the most abundant oxides on average. The chemical weathering indices, such as the CIA (Chemical Index of Alteration) and its modifications, show low-medium values and thus suggest weak-moderate source area(s) weathering conditions, under a mainly dry/arid paleoclimate environment. The low kaolinite amounts confirm a low-moderate degree of weathering processes. The studied samples originate from an environment in which non-steady-state weathering conditions prevailed and active tectonism allows erosional processes. This trend suggests a paleoclimate characterized by persistent dry (arid) conditions alternating with relatively wet (humid) conditions. The studied mudrocks are characterized by recycling effects as recorded in the Al–Zr–Ti plot. The provenance of the studied samples is mainly related to a felsic source such as the rocks composing the Sila Massif. The composition of the studied samples was compared to that of similar samples from the Calcare di Base formation of the Rossano Basin to reconstruct the paleoclimate scenario of the Mediterranean area during the Messinian Salinity Crisis. The analogies between the mudrocks investigated in this work and the argillaceous marls from the Calcare di Base formation of the Rossano Basin suggest that they formed in the same (i) non-steady-state weathering and (ii) dry/arid paleoclimatic conditions. All the evidences allow to hypothesize that semi-closed basins, even if distant and not necessarily synchronous from each other, may have developed in a comparable way due to similar local climate condition, geochemistry of the body water and river run-off. The geochemical and mineralogical proxies from the mudrocks of the Calcare di Base Formation may open a new scenario for the understanding of paleoclimatic condition during the Messinian Salinity Crisis.