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Downcutting and infill of incised valley systems is mostly controlled by relative sea-level changes, and studies on valley-fill successions accumulated independently from relative sea-level or lake-level oscillations are limited. This study focuses on the Plio-Pleistocene evolution of a fluvial drainage system developed in Southern Tuscany (Italy) following a regional marine forced regression at the end of Piacentian. Subsequent in-valley aggradation was not influenced by any relative sea-level rise, and valley morphological and depositional history mainly resulted from interaction between sediment supply and tectonic activity, which caused segmentation of the major valley trunk into localized subsiding depocenters separated by upwarping blocks. Fluvial sedimentation occurred until late Calabrian time, when the major river abandoned that valley, where minor fluvio-lacustrine depocenters allowed accumulation of siliciclastic and carbonate deposits. The present study demonstrates that the infill of the valley was not controlled by the forcing that caused its incision. Accumulation of the fluvial succession is discussed here in relation with localized, tectonic-controlled base levels, which commonly prevent from establishing of a clear downdip stratigraphic correlations. Chronological reconstruction of the study depositional dynamics provides solid constrains to frame them in the tectono-sedimentary evolution of the Northern Apennines. [ABSTRACT FROM AUTHOR]

This study integrates field, geochronological and geochemical data to constrain fluid circulation in the damage and core zone of the seismogenic Monte Morrone Fault System (MMFS), central Apennines (Italy). Faulting along the MMFS evolved from a diffuse deformation at the damage zone towards progressive localisation of a narrower fault core and, finally, to (re)activation of discrete slip surfaces at shallower crustal conditions. Multiple generations of carbonate mineralisations, including veins and slickfibers, occur along the main fault surfaces. Carbonate mineralisations are locally fractured and incorporated in the surrounding cataclasites, documenting repetitive structurally-controlled fluid infiltration during transient episodes of permeability creation and destruction. Stable carbon and oxygen isotopes of the carbonate mineralisations document a dominant meteoric water source probably mixed with deeper circulating waters having longer residence time. Clumped-isotope yield formation temperatures of vein and slickenfibers in the range between 23 and 40 °C. U-Th dating of carbonate mineralisations yield Middle Pleistocene ages (from 268 to 189 ka BP), with a 10–15-ka cyclicity that we link to the coseismic rejuvenation of the structural permeability in the fault zone. We propose that fault-related mineralisations recorded the interactions among tectonic deformation and climate during the Quaternary. Our study is the first documentation of fault-controlled recurrence intervals in fluid infiltration in a seismically active fault of central Apennines. • Fault-related mineralisations record multiple fluid infiltration events. • 10–15 ka cyclicity of fluid ingress is linked with coseismic deformation. • Dated Quaternary syn -tectonic mineralisations are sensitive to climate variations. • Syn-tectonic mineralisations provide an archive for seismic recurrence model. [ABSTRACT FROM AUTHOR]

• Transfer zones play as permeable volumes channeling geothermal fluids. • Travertine deposition is coeval with faulting. • Travertine deposits are useful tools to reconstruct the activity of faults. • The Bagno Vignoni geothermal area is located along active fault segments. • Earthquakes with M < 4 are concentrated along fault segments defining the transfer zone Studying travertine deposits and the network of banded calcite veins that form their roots in the substratum can place important constraints on neotectonic activity and the seismotectonic settings of geothermal areas. In this paper, we present the results of integrated studies of a geothermal area located in the inner Northern Apennines (Bagno Vignoni area, Italy), where low magnitude (M < 4) seismicity suggests the occurrence of active faults, but information on their location, time-span of activity and seismotectonic setting is lacking. The study area is characterised by thermal springs (T<50 °C) and travertine deposits well exposed in saw-cut walls of abandoned quarries. We investigate the relationships between faults and the travertine deposits, in order to reconstruct the syn-sedimentary tectonic activity and the age of faulting, by combining analyses of: i) geological setting and structural/kinematic analyses of faults; ii) travertine morpho-structural and architectural setting; iii) travertine facies; iv) U-Th radiometric, stable- and clumped isotopes of travertine and banded calcite veins. The results highlight the occurrence of a wide brittle shear zone (>3 km) formed by two orthogonal faults systems, NE- and NW-striking, characterised by oblique-slip to normal kinematics, respectively; these faults belong to a tract of the so-named "Grosseto-Pienza" transfer zone, crossing the southern Tuscany from the sea-cost to the outer Apennines belt. The Grosseto-Pienza transfer zone formed with extensional tectonics that have been affecting the inner Northern Apennines since the middle Miocene. U-Th dating of travertine and banded calcite veins indicates that faulting enhanced the hydrothermal fluid circulation since the middle Pleistocene, in an unvaried tectonic setting, as indicated by the δ18O signature and temperature of the hydrothermal fluids, which remained stable through time. The activity of the faults continued until the Holocene and still produces seismicity. Finally, our findings permit to define the seismo-tectonic setting of this sector of the inner Northern Apennines, demonstrating more broadly the utility of travertine deposits in reconstructing the neotectonics in geothermal areas. [ABSTRACT FROM AUTHOR]

The geothermal area of Acquasanta Terme has often been studied for its active and fossil travertine deposits to elucidate fluid origin, geodynamic and hydrological setting. Even though present-day thermal springs are usually used to obtain most information, the three travertine terraces bordering the Tronto river contain a plethora of information. A combination of elemental and isotope analyses (δ18O, δ13C and 87Sr/86Sr-ratio), fluid inclusion microthermometry and U Th dating is used to verify the hydrogeology and its timing. These analyses point out two fluid reservoirs with distinctly different fluids, one with low salinity of 0.7 wt% NaCl eq. and another with 28.5 wt% NaCl eq., which corresponds to the fluid composition of present-day spring fluids. Furthermore, it is demonstrated that geothermal sources were intermittently active in the past 221 ka mainly during uneven-numbered marine isotope stages, which are related to humid, interglacial periods and resulted in three different travertine terraces around 210.5, 126.5, and 36.5 ka. Accordingly, an uplift rate for this area could be estimated at around 1 mm/ka. The fluids were tapped at a depth of approximately 3 km in the tectonized, cataclastic fraction of the Triassic Anidriti di Burano Formation, the Calcare Cavernoso Formation and are originally meteoric based on geochemical evidence of a uniform 87Sr/86Sr-ratio of 0.707914 ± 0.00019 and a δ18O aragonite value of −11.90 ± 0.34‰, which has been depressed by elevated precipitation temperatures between 22.2 and 50 °C. The characterization and dating of fossil travertine deposits gives valuable data providing insights in long-term fluid flow and orogenic uplift rates, adding valuable information to present-day spring fluid characterization. [ABSTRACT FROM AUTHOR]

This work deals with styles and mechanisms of nucleation and development of the Amatrice Fault System (AFS), a regional intrabasinal structure running through the central part of the Amatrice Basin (central Apennines, Italy). The AFS defines a 10 km-long tectonic structure striking NNW-SSE and cross-cutting the late Messinian flysch sequence of the Laga Formation (sandstones and siltstones). The AFS is characterised by the interaction and linkage between structures belonging to a NNW-SSE set (alignment of subparallel fault segments disposed in an en-echelon-like geometry) and to an E-W set (isolated hundred m-long fault segments that interrupt and dislocate the NNW-SSE-striking segments). The occurrence of carbonate mineralisations (in the form of calcite veins and calcite fibres on fault surfaces) along both the NNW-SSE and the E-W sets testifies for fluid flow and fluid-rock interaction during the progress of the intrabasinal faulting. Selected calcite crystallisations were analysed for carbon and oxygen stable isotopes; oxygen isotopes provide evidence of a meteoric water circulation during development of the NNW-SSE-striking and the E-W-striking structures, whereas carbon isotopes of a variable contribution of soil CO2 to the carbon species in solution in the circulating water. Preliminary geochronological (230Th/234U) dating provide Middle-Upper Pleistocene for the development of calcite-filled veins associated with the E-W-striking fault segments. The multidisciplinary dataset is used to depict the AFS as an outstanding intrabasinal fault system in which tectonic deformation and fluid circulation were active during the Pliocene-Upper Pleistocene evolution of the Amatrice Basin. [ABSTRACT FROM AUTHOR]