Tectonic control on travertine and calcareous tufa deposition in a low-temperature geothermal system (Sarteano, Central Italy)

Abstract

This paper presents an integrated study directed toward an understanding of the tectonic control on the hydrothermal circulation and resulting deposition of Middle–Late Pleistocene travertine in a low-temperature geothermal field of southern Tuscany, located in the Sarteano area (Central Italy). The study area is characterized by thermal springs ( c . 25 °C) and related continental carbonate deposits, structurally controlled by SW–NE-trending oblique to strike-slip faults dissecting previous normal faults. Sedimentological–stratigraphical data and 230 Th/ 234 U radiometric age determination for the travertine indicate that continental carbonates were deposited in a tectonically controlled, perched-spring system from 268 ± 22 ka (at least) to the present. The hydrothermal system is (and was) characterized by meteoric waters with a minor contribution from fluids of deeper origin. Meteoric waters infiltrated to depth through tectonically damaged zones of Mesozoic and Cenozoic carbonate rocks and overheated as a result of localized, anomalous geothermal gradient. Then, fluids enriched in bicarbonate–sulphate moved up along highly fractured rock masses at the intersection between strike-slip faults and normal faults. This paper highlights the use of continental carbonates in the reconstruction of palaeohydrothermal systems, in terms of the location of the main conduits for hydrothermal fluid flow, age of faulting and physical properties of hydrothermal fluids.