New 40Ar/39Ar datings on the southeastern sector of the Vulsinian Volcanic District (Central Italy)

Chronostratigraphy of the Montefiascone Volcanic Complex (MVC) and its relationships with the activity of the neighbouring Vulsinian complexes has been investigated by means of 40Ar-39Ar datings. The age measurements have been performed on a volcanic succession whose products have been erupted both from MVC and adjoining volcanic complexes. The older MVC activity has been characterized by eruption of hydromagmatic products interlayered with lava flows. The beginning of this activity has been infererd from the age of the pyroclastic deposit (IgPs: 286 +/- 4.3 ka) directly underlying the Pratalano Ignimbrite (IgP), which is the first product of MVC. The Montefiascone Ignimbrite (IgM: 254.5 +/- 8 ka) marks the onset of the final hydromagmatic activity of MVC, characterized by wet surge deposits. The same fall deposit sampled in three different localities (Pisciarello, Fonte del Noce and Cunicchio) can be recognized as belonging to the final products of the Bolsena-Orvieto Volcanic Complex, on the basis of thickness, chemistry and age (245.3 +/- 4.7, 257.4 +/- 11.2, 253.2 +/- 10.3 ka). Finally, two pyroclastic deposits, a pumice flow sampled at Ponte della Regina and a fall coming from Bolceno could be respectively linked to the first Latera ignimbrite and to the associated fall deposits. The final MVC activity (IgM= 254.5 +/- 8 ka) is almost coeval with the onset of the Latera Plinian activity, which is represented by the pyroclastic levels of Ponte della Regina (243.3 +/- 6.8 ka) and Bolceno (245.9 +/- 5.7 ka). Likewise, the Bolsena-Orvieto Volcanic Complex is characterized at the same time by Plinian eruptions whose products are interlayered with those of MVC.