Geochemical stratigraphy of the Prima Porta travertine deposit (Roma, Italy)

A stratigraphy of a buried travertine deposit was developed using stable isotope geochemistry, trace elements, and radiometric dating. The travertine was identified in a well at Prima Porta (north of Rome, Italy), located at the western boundary of the Tiber Valley, a morpho-tectonic depression of extensional origin. It deposited close to a spring that discharged groundwaters from the nearby volcanic aquifer and was associated with the rise of a deep-seated CO2-rich fluid. The deposition occurred between 53.5 10 ka to 24.2 4.7 ka; its activation was probably coeval with the wettest climatic conditions occurring during Marine Isotope Stage 3, and the end coincided with the cold and arid phase of the last glacial maximum. The chronostratigraphy showed a strong variation in the accumulation rate along the depositional sequence, greater in the lower half and much slower in the upper part, with a sharp decrease in the accumulation rate occurring between 47 and 43 ka. Isotope and chemical stratigraphy described a temporal evolution of events that are correlated to the global climatic variability; palaeoclimatic changes, in fact, influenced the hydrological regime and indirectly the tectonic activity by modulating the emission of deep CO2, the chemistry of the groundwater, and ultimately the precipitation of the travertine.