Modello strutturale della deformazione estensionale paleogenica nella ex-cava Main (Arzignano, Vicenza)

In the eastern Lessini Mountains (Vicenza) at the confluence of the Chiampo and Agno valleys on the southern slope of Monte Main, a "Chiampo marble" quarry was active in the 1980s, well known for its very rich paleontological finds. The exceptional exposure produced by the excavation, is approximately parallel to the extension direction of the Alpone-Agno graben, a Paleogene structure coeval with the mafic to ultramafic magmatism of the western Veneto and the southern Trentino,. This allowed the observation of several normal faults which accommodated the extension. Three carbonate banks interlayered with stratified basaltic epiclastics show an eastern dip increasing downwards, while the thickness of the stratified epiclastics increases rapidly eastwards. The triangular-shaped section, presently partly obliterated and inaccessible, could be interpreted as the infilling of a basin developed on the hanging wall of a synsedimentary listric fault dipping west, or on the roof of a hectometric carbonate block eastward tilted in a domino model. At a larger scale the domino style is shown also by the intermediate carbonate bank. This deformation style explains well the rapid thickness variations of the epiclastics observed throughout the entire graben area.