Origin and deposition of the Lapis Tiburtinus travertine
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 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.
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The Colli Albani volcano (also Alban Hills volcano) is the large quiescent volcanic field that dominates the Roman skyline. The Colli Albani is one of the most explosive mafic calderas in the world, associated with intermediate to large volume ignimbrites. At present it shows signs of unrest, including periodic seismic swarms, ground uplift and intense diffuse degassing, which are the main short-term hazards. New studies have discovered deposits related to previously unknown pre-Holocene and Holocene volcanic and phreatic activity. In the fourth Century B.C.E. Roman engineers excavated a tunnel through the Albano maar crater wall to keep the lake from breaching the rim and flooding the surrounding countryside, events that had previously destroyed this region several times.
The Colli Albani Volcano contains 21 scientific contributions on stratigraphy, volcanotectonics, geochronology, petrography and geochemistry, hydrogeology, volcanic hazards, geophysics and archaeology, and a new 1:50 000 scale geological map of the volcano. The proximity to Rome and the interconnection between volcanic and human history also make this volcano of interest for both specialists and non-specialists.