Stratigraphy of the Miocene syn-rift volcano-sedimentary succession in a sector of the central-southern Sardinia Trough (Italy)

The Miocene sedimentation in the "Sardinia Trough" has been controlled by tectonic activity, also responsible for strong, basic-intermediate and silicic calc-alkaline volcanism. The volcano-sedimentary succession cropping out near the Villanovaforru village ("Marmilla Basin", central-southern "Sardinia Trough") is the object of this study. The succession has been subdivided into nine new stratigraphic intervals and it is characterized by abundant volcaniclastic materials. In the lower part of the succession some basaltic pillow lavas are interbedded. The nine stratigraphic intervals extend from Early Burdigalian (Zone N5 and N6) to Late Burdigalian (Zone N7) and the microfossil assemblages indicate hemipelagic sedimentation. A deepening of the basin seems to occur in correspondence to the beginning of the volcanic activity. The reconstructed stratigraphic succession of the Villanovaforru area, which is considered representative of the Early Miocene sedimentation within the southern sector of the "Marmilla Basin", shows that a transition from a continental to a marine environment occurred during the "Sardinia Trough" rifting and the drift of the Sardinia-Corsica Block. The extensional tectonics is also confirmed by the high-Mg composition of the basaltic lava flows interbedded in the succession.