Stratigrafia e caratterizzazione delle vulcaniti attraversate dal pozzo David Lazzaretti

An exploration well named "David Lazzaretti" (pDL) was drilled, during the year 2010, by the Tuscan regional authority, in the southern part of Mt. Amiata volcano in order to gather data for hydrogeological purposes. pLW was drilled near the village of Santa Fiora (GR), close to the Poggio Trauzzolo lava dome at an altitude of 1086 m above sea level (a.s.l.), it reached a depth of 545 m below ground level (b.g.l.; i.e. 541 m a.s.l.) and was almost entirely continuous core recovered except the superficial 60 m. pLW crossed the volcanic complex and, at 530 m b.g.l., reached the sedimentary substratum, consisting of deformed greenish shaly sediments with interbedded layers of very fine-grained siliceous limestones (i.e. Palombini shales outcropping in the southern side of the volcano). We studied the sequence encountered by pDL in order to investigate the volcanic stratigraphy, and carrying out facies analyses, textural, and petrographic characters. In the drilled volcanic sequence, mainly two lithofacies associations are identified and interpreted respectively as lava flows and lava domes. As a whole, the core succession is indicative of an aggradation of effusive products for about 500 m thickness and there is no evidence of pyroclastic deposits and/or mega-breccia facies. The study of pDL allowed the gathering of a data-set useful to complete the stratigraphy of the Mt. Amiata volcanic sequence, in fact oldest volcanic units has been found inside the drilled sequence, under the known outcropping volcanic.