Abstract
The Quaternary stratigraphic record of Jebel El Mida, composed of continental deposits, is a useful example of concomitant travertines and alluvial deposition in an extensional setting. Travertine deposition occurred in a faulted Pleistocene alluvial fan giving rise to seven (recognised) facies interfingering with five other alluvial ones. The travertine depositional events indicate a tectonically driven evolution from terraced slope (facies group FC1–FC6) to a travertine fissure ridge-type depositing phase (facies group of FC1–FC7). Interfingering between travertine and alluvial facies indicates the co-existence of adjacent and time-equivalent depositional environments. The travertine deposition resulted from deep origin hydrothermal fluids channelled along damaged rocks volumes associated to a regional fault system, named as the Gafsa Fault (GF). The travertine–terrigenous succession in Jebel El Mida highlights the major role played by the GF in controlling: (i) the hydrothermal fluid flow, still active as also indicated by the numerous thermal springs aligned along the fault zone; (ii) paleoflow directions, discharge locations, volume, rate and fluctuations of the water supply. The paleoclimatic correlation with adjacent localities reveals that, at that time, humid episodes could have contributed to the recharge of the hydrothermal system and to the deposition of alluvial sediments.
Highlights
Travertine is a thermogene continental carbonate deposit associated with thermal springs, and whose deposition is induced by CO2 outggassing favoured by the fluids’ pressure drop, turbulence of running water and microbial activity (Pentecost, 2005)
Travertine deposits are relevant in providing helpful elements for geological reconstruction (Brogi, Capezzuoli, Aqué, Branca, & Voltaggio, 2010; Brogi et al, 2016; Chafetz & Folk, 1984; Ford & Pedley,1996; Gandin & Capezzuoli, 2008; Guo & Riding,1999; Pentecost, 2005)
Restricted by the exposure of the travertine–terrigenous succession in the field (Figure 4(A)), six representative sections were logged and described (Figure 4(B)) in which sedimentary structures, lithologic components, stratigraphic relationships and geometry of the rock strata were recorded in detail in order to define the fabric types, their lateral and vertical multi-scale variations and the depositional processes governing their deposition and the environment in which they were deposited
Summary
Travertine is a thermogene continental carbonate deposit associated with thermal springs, and whose deposition is induced by CO2 outggassing favoured by the fluids’ pressure drop, turbulence of running water and microbial activity (Pentecost, 2005). Travertine deposits are relevant in providing helpful elements (i.e. paleoclimate, paleoecology of the spring system, tectonic setting, paleohydrology, paleotopography and thermal history) for geological reconstruction (Brogi, Capezzuoli, Aqué, Branca, & Voltaggio, 2010; Brogi et al, 2016; Chafetz & Folk, 1984; Ford & Pedley,1996; Gandin & Capezzuoli, 2008; Guo & Riding,1999; Pentecost, 2005). The depositional morphologies include multisymmetrical bodies such as mounds, slopes and ridges (Gandin & Capezzuoli, 2014). They are distinguished from tufa by the abundance of coated gas bubbles and shrub lithofacies (Guo & Riding, 1999). The travertine deposition is scarcely influenced by anthropogenic or climate-controlling factors (Gandin & Capezzuoli, 2014)
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