GNGTS 2018 - 37° Convegno Nazionale

234 GNGTS 2018 S essione 1.2 layers. Towards the SE, the youngest alluvial fans are truncated by ~3 to 5 m high, SW-facing rectilinear scarp. Borehole data indicate that the alluvial fan deposits are at least 50 m thick. They pass, at depth, to a ~100 m thick sequence of volcanic and marine to transitional environment deposits. Marine to transitional environment deposits, which are ~30 m thick, lay on top of carbonate rocks and are covered by a ~70 m thick succession of volcanic deposits. The latter include the Campana Ignimbrite (hereinafter C.I.) regional stratigraphic marker, aged 39 ka (De Vivo et al. , 2001). The C.I. layer, which is 30 m to 40 m thick, separates “pre-C.I.” volcanic deposits (~20 m thick) from “post-C.I.” volcanic deposits (~10-20 m thick). The combination of field and borehole data allowed us to construct geological cross-sections representative of the geological setting of the Lavorate basin and adjoining Sarno plain. Figure 2 shows one of the cross sections (Section A-A’). Discussion and conclusion. The geomorphological analysis of the northeastern margin of the Sarno plain, and detailed borehole log data from the Lavorate basin provide new information on the recent, Late Quaternary, evolution of southern part of the Campania plain graben. Subsurface stratigraphy data allow identifying a ~10-20 m thick “pre-C.I.” volcanoclastic unit. Pyroclastic deposits underlying the C.I. have been correlated by Aprile and Toccaceli (2002) with the Taurano Ignimbrite, aged 157.4 ±1 ka (De Vivo et al. , 2001). Based on such a correlation, a late Middle Pleistocene age is inferred for the marine to transitional environment deposits underlying the pre-C.I. volcanics. In contrast, Cinque et al. (1987) correlated the marine to transitional environment deposits underlying the pre-C.I. volcanics to the Euthyrrenian (125 ka). In this second hypothesis, an Upper Pleistocene age is inferred for the pre-C.I., which could be correlated with the Durazzano Ignimbrite, aged 116 ka (Rolandi et al. , 2003) and found, in several sites along the NE border of the Campana plain, below the C.I. deposits, with a paleosoil separating the two volcanic deposits (Bellucci et al. , 2003). The nature of the pre-C.I. pyroclastic unit is not constrained by our data and, consequently, the age model for this unit and the top part of the underlying marine to transitional environment unit (both of which being not older than the late part of the Middle Pleistocene) remains undefined. However, new information on both the structural setting of the investigated area and Fig. 2 - Geological cross sections of the study area. Location is reported in Fig. 1.