Late Quaternary evolution of the north-eastern margin of Campania Plain (southern Italy).

The Campania Plain - a broad, complex graben closely controlled by NE-SW, NW-SE and E-W normal fault activity, established in Late Pliocene (IPPOLITO et alii, 1973) or the Early Pleistocene (CINOUE et alii, 1987; 2000) along the Tyrrhenian side of the Apennine Mountains - has been the object of several important studies of its geological setting characterized by the interplay between volcanism, tectonics and sedimentation (IPPOLITO et alii, 1973; ORTOLANI & APRILE, 1985; BRANCACCIO et alii, 1995; ROMANO et alii, 1994; APRILE et alii, 2004). This investigation focuses on the geological characteristics of the Caserta town area and, through the analysis of data from subsurface and field surveys, it aims at defining more precise stratigraphic constraints on them northeastern region of the Plain. Geological data derive from the study of some 300 lithostratigraphic logs from boreholes reaching a 60 m maximum depth. Deeper lithological data (to a maximum 400 m depth) were obtained from boreholes drilled for hydrogeological surveys. Some additional subsurface information was obtained from well samples and from quarries. The key to correlation of the different units is the Campanian Grey Tuff (TGC in the present paper) (similar to 39 Ky B.P. DE VIVO et alii, 2001) and Durazzano Ignimbrite (116 Ky B.P., ROLANDI et alii, 2003) the stratigraphic marker beds in the investigated area. The reconstructed stratigraphic sequence ranges from Middle-Late Pleistocene to Recent. Above the faulted Apennine carbonate bedrock, five units have been defined: two are of marine-transitional facies (M1 and M2) and have been recognized exclusively in the subsurface; the other three units (V1, TGC, TGN) consist mainly of pyroclastic deposits. The Middle to Upper Pleistocene marine-transitional formation (M1) is at the bottom of the succession. The unit is overlain by mostly incoherent volcanic deposits (V1), which are correlatable with the Durazzano Ignimbrite (116 Ky B.P., ROLANDi et alii, 2003) outcropping along the eastern border of the Plain. A prevalently continental stage follows, consisting mainly of reworked VI lithologies and detrital-colluvial deposits (V1a) produced by the weathering along the carbonate uplands. On top of these deposits and far from the carbonate mountains, transitional units (M2) have been recognized. The pyroclastic flow deposits of the Campanian Grey Tuff (TGC) overlie the two units: they blanket the whole area filling morphologic depressions and dipping gently toward the central region of the Plain. The uppermost unit of the reconstructed stratigraphic succession is represented by thin deposits of the Neapolitan Yellow Tuff (TGN, 15 Ky B.P. DEINO et alii, 2004). A subsequent continental stage is witnessed by Upper Pleistocene to Recent alluvial and detrital-colluvial deposits covering the two volcanic units. The reconstructed geological sections, and the recognition of the depths to the top of the main lithostratigraphic units occurring mainly in the subsurface, has allowed the tectono-sedimentary evolution during the middle-late Pleistocene to be detailed. The main faults displacing the mid-Cenozoic carbonate bedrock have N150-160 degrees, N120 degrees and E-W orientations. They were reactived during the Late Pleistocene (after the deposition of the M1 and V1 units) and resulted in the displacement by about 50 m of the M1 and V1 units toward southwest. Fault planes, active during the Late Pleistocene, are sealed by the TGC deposits. Locally, even slight displacements of the TGC unit can be detected. The stratigraphic data have been stored in a MS Access database. Processing of these data into a Geographic Information System (GIS) project has allowed the construction of a digital surface model (DSM) of the bottom and top of the subsurface units. Knowledge of such a geological setting may also represent the basis for correct planning and efficient management of this highly urbanized area.