A global travertine GIS database – synthesis and implications for pre-salt reservoir targets

Travertine deposits are widespread in tectonically active settings, especially in rift systems, and potentially form pre-salt reservoirs in the South Atlantic. Travertine has been studied for more than a century, and there are large amounts of published data on the facies, depositional processes and water chemistry of associated springs. However, the literature is widely scattered and frequently difficult to access. Geographic Information System (GIS) technology can be used to assemble all information together by 1) cataloguing the spatial characteristics of (travertine morphology/facies and their associated springs) and 2) integrating observed images, analytical results and geological background elements into a single and standardized database.

This study has established an initial global travertine GIS database that contains 53 provinces located in 22 countries. The database can be used as a research tool to visualize and compare the spatial distribution of travertines and their geometric relationships. The database also enables users to assess the relationships between: 1) travertine deposition and spring chemistry; and 2) travertine deposits and geological background elements (such as faults, volcanoes and limestones, with which travertines are typically associated). Ultimately, the database provides a valuable resource for synthesizing and generating conceptual models.

Based on the GIS database, we conclude the following:

1) travertine formation occurs are mainly in rift systems, but also in strike-slip to transtensional systems;

2) travertines are formed in subaerial and sublacustrine environments;

3) travertine morphologies (megascale: 10s-100s m to km) can be characterized as flat top platforms, step-like mounds (large scaled terraces) and valley-filling belts in hillslope topographic settings and as fissure ridges, cones-mounds-mound complexes, and flats-pools in quasi-horizontal topographic settings.

We also propose the concept of Travertine Window as an approach to predicting travertine occurrence. Travertine can start to form at the beginning of rifting and continue more or less throughout the rifting phase. In these cases, in the absence of siliciclastics, travertine deposits can form most of the extensional basin fill such as Itaboraí in Brazil. In other cases, such as the Denizli Basin of Turkey and much of the central Italy, travertine deposits appear to have developed during the later stages of rifting. At these locations, travertine deposits are patchy and mostly scattered along basin margins. All travertines typically form in phases that were interrupted by intervals with little or no carbonate precipitation. This would suggest that travertine forms under potentially predictable conditions reflecting variations in tectonic and/or climate state.

These synthesized models have important implications for reservoir targeting and model-building strategies in pre-salt fields.