Tertiary Extension in the Southern Trento Platform, Southern Alps, Italy

The southern Trento Platform (Southern Alps, NE Italy) was the locus of abundant mafic volcanism associated with Paleogene extensional tectonics. During the Paleocene and throughout the Eocene, a NNW-SSE trending graben (the Alpone-Agno Graben (AAG)) developed in the eastern Lessini Mountains. The graben was filled with basaltic volcaniclastics, calcarenites, and lava flows. The AAG is a half-graben system probably bounded by rotational listtic normal faults. Most faults in the graben dip towards the WSW. Paleostress analysis within the AAG shows that during the Eocene the direction of horizontal extension was ENE-WSW. The volcanic activity continued into the Oligocene; however, the relation between Oligocene tectonics and volcanism remains unclear. Gravimetric and magnetic anomalies in conjunction with the crustal thickness variations suggest a locus of lithospheric thinning slightly off-axis from the AAG. This can be explained by an overall asymmetric extensional geometry dominated by a WSW dipping detachment fault. The Paleogene geodynamic scenario of the Trento Platform suggests that the AAG developed as a foreland extensional response to the active collisional convergence between the European and Adriatic plates. Neogene compressional tectonics reactivated some of the Paleogene normal faults as strike-slip faults.