Faulting-hydrothermal circulation relationships constrained by thermogene travertine dating, Albegna Valley, Italy

This work presents preliminary geochronological (230Th/234U) and structural data carried out on the travertine deposits and country rock units outcropping in the Albegna Valley, central Apennines, Italy. Travertine, lying in unconformity on top of Neogene-Pleistocene deposits, forms N-S aligned bodies in areas characterized by both fossil and active hydrothermalism. E-W and N-S striking fault systems, with dominant strike-slip and subordinate transtensive kinematics, have been recognized as affecting the travertine bodies. In the study area, travertine morphotypes include fissure ridge and sub-horizontal plateau, where travertine deposited in oblique to sub-vertical banded and bedded depositional styles, respectively. The U-series dating has been applied to selected samples coming from the different bodies. The obtained ages span from > 350 ka (for the northern fissure ridge) to about 40 ka moving southwards, where hydrothermal outflow is still active. The geochronological method has been also used for constraining the age of crosscutting relationships between bedded and banded depositional styles. The integration of the results suggests a hydrothermal setting characterized by a strong structural control and by a spatial and temporal evolution during the late Quaternary in the region.