GNGTS 2013 - Atti del 32° Convegno Nazionale

Discussion and concluding remarks. On the regional scale, the spatial distribution of large, mappable travertine bodies does not follow that of the major springs, discharging from the main aquifers of the study area, i.e. those hosted in the carbonate successions. Conversely, a striking spatial association between the late Pleistocene-Holocene deposits and the main (around 10 km in length, and with large offsets) extensional faults with coeval activity is observed (Fig. 1; Ascione et al ., 2013a). All such recent travertines, as well as currently depositing ones, are characterised by positive carbon isotope (d 13 C) values (Tab. 1), which indicate that their precipitation is driven by a supplementary –non-atmospheric– source of CO2. This would produce more aggressive water–rock interactions at depth, able to trigger –in favourable hydrogeological conditions– the production of geologically significant deposits (Ascione et al ., 2013a). Overall evidence from the study area suggests that the additional CO2 source is provided by active faults, further pointing to the long evidenced major role of extensional fault zones, and particularly active faults, in the migration and degassing of deep-seated fluids in non-hydrothermal areas (Kerrich, 1986; Sibson, 2000; Toutain and Baubron, 1999; Cello et al ., 2001; Ciotoli et al ., 2007). Therefore in the southern Apennines, as well as in other tectonically active areas worldwide (e.g., Hancock et al ., 1999), a link between conspicuous continental carbonate accumulation and active faults of regional relevance is evidenced. This implies that, independent from their facies (stiff travertines vs. porous tufa), large continental carbonate deposits may be considered as indicators of persistent fault activity. Based on such evidence, the time-space distribution of the southern Apennines large travertine bodies may be considered as a tool for the reconstruction of the tectonic history of the region. Particularly it may provide information constraining both the location and age of activity of major extensional structures, i.e. of well-developed extensional faults, accumulating large offsets. Based on such assumption, the presence of uplifted travertine bodies in the margin of the Sele Plain coastal graben would suggest a seaward migration of both fault activity and main depocentral area over the Early to Middle Pleistocene time span, which is consistent with independent morphotectonic reconstructions (Brancaccio et al. , 1987; Brancaccio et al ., 1991; Amato et al ., 1992) based on both surface and subsurface information. Similarly, migration of fault activity in the Alburni Mts. – Tanagro valley – Mt. Marzano area in the Middle to Late Pleistocene time span (Ascione et al ., 2013b), is mirrored by a coeval shift in the travertine depositional loci. Conversely, the occurrence along the Campania Plain boundaries of superposed travertine layers progressively buried in the subsurface would suggest persistent activity of the faults bounding the Plain from the Middle Pleistocene to the Holocene, which is consistent with absence of uplifted Quaternary deposits along the boundaries of the Campania Plain. All above evidence indicates that activation/deactivation of extensional faults is accompanied by a parallel activation/deactivation of associated phenomena, e.g. deep seated fluid advection and, in those areas in which soluble rocks are present (either outcropping or buried), dissolution and related carbonate precipitation. Furthermore it suggests that significant amounts of continental carbonates represent a record of fault activity, their ages helping constraining the age of faulting and faulting chronology. References Amato A., Ascione A., Cinque A., Lama A.; 1991: Morfoevoluzione, sedimentazione e tettonica recente dell’Alta Piana del Sele e delle sue valli tributarie (Campania). Geogr. Fis. Dinam. Quat., 14 (1), 5-16. Amato, A., Cinque, A., Santangelo, N. and Santo, A., 1992., Il bordo meridionale del Monte Marzano e la valle del F. Bianco: geologia e geomorfologia: Studi Geologici Camerti, volume speciale (1992/1) 191-200. Amato, V., Anzalone, E., Aucelli, P.P.C., D’Argenio, B., Ferreri, V., Rosskopf, C.M.; 2012: Sedimentology and depositional history of the travertines outcropping in the Poseidonia-Paestum archaeological area. Rendiconti Lincei 23, 37-44. doi:10.1007/s12210-011-0155-z. Anzalone, E., Ferreri, V., Sprovieri, M. and D’Argenio, B.; 2007: Travertines as hydrologic archives: The case of the Pontecagnano deposits (southern Italy): Advances in Water Resources v. 30, p. 2159-2175. Ascione, A., Cinque, A., Tozzi, M.; 1992: La Valle del Tanagro (Campania): una depressione strutturale ad evoluzione complessa. Studi Geologici Camerti, Spec. Vol. 1992 ⁄ 1, p. 209-219. 15 GNGTS 2013 S essione 1.1