Origin and deposition of the Lapis Tiburtinus travertin

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-km2 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 Q1 oriented margin is controlled by dextral strike–slip faults and associated N20–408E 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