Palaeomagnetic controls on the emplacement of the Neapolitan Yellow Tuff (Campi Flegrei, Southern Italy)

Abstract: Two outcrops of Neapolitan Yellow Tuff at Torregaveta and Posillipo have been investigated palaeomagnetically. Analyses of low blocking temperature components, in association with mineralogical, volcanological nd magnetic anisotropy data, suggest the following sequence of events: (i) deposition of pyroclastics at temperatures not lower than 275 ~ at least at Torregaveta; (ii) cooling associated with zeolitization and modification of the original positions of the clasts; (iii) further dislocation of the clasts after cooling; and (iv) lithification. Such a model reconciles otherwise conflicting volcanological nd palaeomag-netic data. The Neapolitan Yellow Tuff (NYT) is the major pyroclastic tuff deposit in Campi Flegrei and comprises pumices, obsidian fragments, crystals and lithics embedded in an ashy matrix. The pyroclastic deposit is inferred to cover at least 500 km 2 and to have a volume of about 40 km 3 (Orsi et al. 1992). They are dated around 12 k