Geothermally-controlled microbial carbonates in a tufa system: an example from the Triponzo area (Central Italy)

In the last decade, continental carbonates accumulated in rift basins have been increasingly studied as a valuable archive of information about Quaternary palaeoclimate, palaeohydrology and groundwater isotope geochemistry and... [ view full abstract ]

In the last decade, continental carbonates accumulated in rift basins have been increasingly studied as a valuable archive of information about Quaternary palaeoclimate, palaeohydrology and groundwater isotope geochemistry and tectonics. In addition, recent discoveries of Cretaceous Pre-salt hydrocarbon reservoirs in the subsurface of the South Atlantic, offshore Brazil and West Africa, have led to an increased interest about microbial carbonates accumulated in continental rift basins.
Despite numerous and significant studies, the current knowledge about non-marine carbonate facies models, processes and products of subaqueous and subaerial spring-related carbonate precipitation is still limited, especially about the various precipitation processes (inorganic, biologically controlled and microbially mediated) taking place in continental aquatic settings, where the biologically induced and influenced mineralization is controlled by a complex interaction of multiple factors (geochemistry, hydrology, microbial communities…).
A better understanding of depositional and spatial models of carbonates in continental rift settings can be achieved by extracting spatial information from present-day systems to produce predictive tools for subsurface exploration of such carbonate reservoirs.
Triponzo (central Italy) is a small village situated on the Nera River and characterised by the presence of a Quaternary, partially dismantled barrage tufa system and an active small thermal spring (about 30°C) located upstream of the tufa site.
Along the right side of the Nera River, several small outcrops characterised by the presence of unusual carbonate facies stratigraphically correlable with the tufa system are present.
Sedimentological, petrographic and geochemical analysis of such deposits evidence their microbially mediated origin and their strict correlation with the local geothermal circulation along the present fault/fracture network.
The study of the Triponzo microbialites can contribute to the better knowledge of the biologically controlled and microbially mediated processes leading to the carbonate deposition in the non-marine carbonates realm.