|
|||||
|
|
Isotope geochemistry, petrology and depositional environments of the diatomite-dominated Tripoli Formation (Lower Messinian), Sicily |
|
| Authors: | A BELLANCA S CALDERONE R NERI |
| Institution: | Istituto di Mineralogia, Petrografia e Geochimica, Via Archirafi, 36, 90123 Palermo, Italy |
| Abstract: | ABSTRACT The Tripoli Formation (Lower Messinian) in Sicily includes diatomites irregularly alternating with marl and carbonate beds and lies, stratigraphically, between the Tortonian pelagic marls and the evaporitic Calcare di base. The relationships between mineralogy, textural features and oxygen-carbon isotopic compositions of carbonate components point to a wide variability of depositional conditions and suggest that Tripoli sedimentation occurred in small basins characterized by periodic and marked restriction from the open sea. The isotopic values of calcite and dolomite in the diatomites suggest an evolution from normal marine towards more restricted environments. Evaporating conditions are also indicated by the occurrence of anhydrite, length-slow chalcedonic quartz and moulds of gypsum. In a more advanced stage, the precipitation of heavy δ The deposition of marl and carbonate beds alternating with or overlying the diatomites took place in an environment with highly evaporated marine waters on the basis of δl |
| Keywords: | |