Abstract We describe the origin and evolution of a travertine deposit located 20 km east of Rome (Italy), near Tivoli. Borehole analysis reveals that the Tivoli travertine body was deposited in a 20-km 2 basin, has an average thickness of 50 m and is thicker (more than 80 m) along a steeper base along the west north–south striking side. Structural analysis reveals that this north–south oriented margin is controlled by dextral strike–slip faults and associated N20–40°E oblique and normal faults and joint system that serve as a preferential pathway for hydrothermal circulation, linked to mixing between a shallow fresh water table and deeper circuit. The age of the travertine was calculated by means of U-series disequilibrium, with the beginning and end of the deposition dated at c . 120 and 30 ka, respectively. Five unconformities within the travertine sequence may be linked to erosional episodes related to fluid discharge and low sea level. We conclude that the growth of the Roman thermogene travertine, and therefore the upwelling of hydrothermal fluid along the fault zone, was favoured by a warm and humid climate.

Abstract Travertines are accumulations of calcium carbonate in springs (karstic, hydrothermal), small rivers, and swamps, formed mainly by incrustation (cement precipitation and/or biochemical precipitation). The term travertine has a local origin from Tivertino, the old Roman name of Tivoli in Italy where travertine forms an extensive deposit. It has already been used by Lyell, 1863; Cohn, 1864; Weed, 1889; and Howe, 1932. These deposits have also been reported as tufa, calc tufa, calcareous tufa, plant-tufa, carbonate concretions, petrified moss, Vaucheria tufa, Chironorriid tufa, spring-sinter, calcic-sinter, sinter crust, and others, and by local names. The term tufa refers to highly porous, spongy deposits, and was already used by Plinius (thophus) for incrustation on vegetal remains and porous volcanic rocks. According to Pia (1933), the term sinter should be restricted to those deposits of an abiotic origin that are typically more dense and compact than tufa; most probably sinter-crust includes flowstones and other speleothems. In order to avoid semantic confusion, the present trend is to designate as travertine all the carbonate incrustation on plant remains (in place and debris) without reference to the pore volume or density. As a matter of fact, many fossil travertines are very dense because of complete cementation of all the originally abundant cavities. Travertines can form on higher and lower plants, but most commonly on algae (blue-green, green), mosses, hepatics (Fig. 1) and on insect larva caparace (Chironomids) (Fig. 2), and in some cases they may be considered as stromatolites. Published works on recent and subrecent travertines are numerous, dating from the 19th and 20th centuries.