I “TRAVERTINI” IN ITALIA: PROPOSTA DI UNA NUOVA NOMENCLATURA BASATA SUI CARATTERI GENETICI.

Abstract

Capezzuoli E. & Gandin A., The “Travertine” in Italy: proposal of a new nomenclature based on the genetics characters.
(IT ISSN 0394-3356, 2004).
The word “Travertine” in the common Italian language, is generally used for a variety of continental carbonates deposited by hot- or
cold-waters, in the surroundings of spring vents, or in fluvial, palustrine or lacustrine systems. The geochemical signature as well as the lithological and petrographic features of these limestones, appear to be controlled by the physiochemical conditions of the spring
waters and/or the depositional environment and climate. The results of recent research indicates that the petrologic features can be
used for a genetic classification. The term Travertine, which for a long time has been used to designate the ornamental/building stone
quarried in the thermal deposits of Tivoli, should be reserved to calcium carbonate deposits associated to hydrothermal spring
systems. This lithology which is slightly enriched in 13C, TDIC, strontium and sulphur, appears to be hardly dependent upon climate. It
is characterized by a primary, low-porosity crystalline fabric, fine daily laminae, and by bacteria and cyanophytes as the dominant organic components. On the other hand, the term Calcareous tufa, coined in the British literature, refers to calcium carbonate deposits formed under a cool water regime, around karst spring complexes and/or in a fluvio-palustrine environment. This lithology which is depleted in 13C and shows TDIC concentrations more or less in equilibrium with the soil atmosphere, appears to be highly dependent upon climatic factors. It is characterized by normally low depositional rates, poor bedding, commonly lenticular, highly porous bodies and abundant remains of micro- and macrophytes, bacteria and invertebrates. The distinction between these two groups of lithotypes is not univocal since the cool water Calcareous tufa deposits are often found as the natural lateral prosecution of Travertines far from the thermal-spring complex. However preliminary, compared analyses of Travertine and Calcareous tufa fabrics show the possibility of
using petrographic criteria for their distinction. The discrimination of the two types of deposits appear to be essential in the interpretation of the tectonic, climatic and anthropologic meaning of the fossil continental carbonates. For this reason, it is important that the scientific community working on continental carbonates adopt even in Italy a suitable terminology reserving the term Travertine for the deposits deriving from hot-spring complexes, and Calcareous tufa for the sediments deposited near cold water springs and in fluvialpalustrine systems.