Rilevamento geologico di dettaglio e analisi stratigrafiche dell'area attorno al Monte Zenone (Tremosine, BS).

The purpose of this work is to analyse the Norian-Rhaetian intraplatform basin in the area of M. Zenone (Tremosine, BS), highlighting the stratigraphic relationships between the different mapped Formations, that are the Dolomia Principale and Calcare di Zorzino Fms. A detailed geological survey (1:10.000) was carried out in attempt to reconstruct the original sedimentary basin, recognizing four different lithofacies, here considered as different units: Dolomia Principale s.s., Calcare di Zorzino s.s., Breccia and Dolomitized Bioherm. The result of such analysis points to heteropic relationships between the lithofacies, due to the fact that the near-margin Breccia bordered between the basinal limestone and the carbonate platform and bio-constructed mounds are contained in the Calcare di Zorzino limestone, which proves that different early mounds (which later formed the Bioherm) grew alongside with the Calcare di Zorzino Formation. The relationships between the lithofacies throughout the area in exam appear to be slightly affected by alpine tectonic. The faults recognized during the survey testified a Triassic extensional tectonic system, successively reactivated as strike-slip faults. An attempt to a biostratigraphical analysis was carried out, although without success. However, the only collected conodont fragment from 2 samples of the Calcare di Zorzino (4-kg-each) permits to understand the maturity of the organic matter. This fragment has CAI=1,5 (Conodont Alteration Index), which brought to the conclusion that the oil present in fractures and cavities of the rocks migrated from other Formations, probably from the Argillite di Riva di Solto, located northwards