Interdigitated fluvial clastic deposits and calcareous tufa testifying an uplift of the catchment area: An example from the Pianizzoli area (southern Tuscany, Italy) Ivan Martini ⁎, Enrico Capezzuoli Department of Environment, Earth and Physical Sciences, University of Siena, via Laterina 8, 53100 Siena, Italy abstract article info Article history: Received 12 August 2013 Received in revised form 30 October 2013 Accepted 3 November 2013 Available online 11 November 2013 Editor: B. Jones Keywords: Calcareous tufa Climate vs. tectonic Southern Tuscany Apennines Calcareous tufa, as well as other types of continental carbonates, are largely sensitive to climate variations. As a consequence, the relationship between climate variations and tufa deposition is relatively well known and calcareous tufa deposits are often used as a reliable climatic proxy in many geological settings. Conversely, the response of tufa to tectonics and uplifting processes is relatively poorly known, due to their genetic independence from geothermally heated groundwater springs and associated tectonic-controlled upwelling conduits in tecton- ically active settings. The aim of this paper is to describe a peculiar stratigraphic succession where calcareous tufa deposits are closely associated and interbedded with coarse-grained clastic deposits. The study area is located in southern Tuscany (Massa Marittima), where extensional tectonic processes, responsible for the emplacement of magmatic bodies at shallow crustal levels, have been active from Pliocene to Quaternary age, and caused a diffuse uplift as well as local volcanic eruptions and hydrothermal fluid circulation. The succession described in the paper recorded phases of calcareous tufa-dominated deposition (i.e. overall, medium/low hydrodynamic energetic settings) repeatedly interbedded with coarse-grained clastic fluvial sediments which testify an abrupt change in both the energy of the depositional environment and the sed- iment supply. Nevertheless, during the phases dominated by clastic sedimentation, tufa deposition was not inhibited as it would be expected for climate-influenced settings, suggesting that the observed stratigraphic settings were a consequence of a local uplift of the catchment area. These findings indicate that calcareous tufa deposits could be a sensitive proxy to tectonics when they are asso- ciated with coarse-grained clastic deposits, in a geological setting where the origin of the clastic sediments cannot be explained by autocyclic or climate-induced factors. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Understanding the role of external driving forces (e.g. climate, eustasy and tectonism) on sedimentation patterns is of outstanding im- portance in sedimentary geology. This is emphasized in the study of Quaternary deposits, which commonly provide important elements to neotectonic and/or palaeo-climatic reconstructions. Distinguishing the effects of different forcing factors in ancient deposits however is often a difficult task to address. This is particularly true for continental succes- sions, whose response to external driving forces is not always straight- forward to understand (Schumm, 1977; De Wet et al., 1998; Blum and Törnqvist, 2000; Pla-Pueyo et al., 2009; Alonso-Zarza et al., 2012; Blum et al., 2013; Vázquez-Urbez et al., 2013). Calcareous tufa deposits are a type of terrestrial limestones formed by precipitation of carbonate minerals from ambient-temperature water bodies (Ford and Pedley, 1996; Pedley, 2009; Capezzuoli et al., in press; Gandin and Capezzuoli, 2008). The deposition of tufa and relat- ed facies is common in many fluvial systems characterized by flowing waters which are rich in dissolved carbonate/bicarbonate and calcium (Arenas-Abad et al., 2010). The close relationship between climate and tufa deposition has been widely evidenced (Pentecost, 2005; Andrews, 2006 and references therein). The presence of fossil tufa systems in sedimentary records testifies important climatic changes in the geological record. For example, rainfall availability is a key factor for tufa deposition as it sustains the groundwater flow and provides a carrier for the dissolved carbon dioxide. This intimate relation has been demonstrated in distal glacial transitional environments and for glacial periods (South Europe — Capezzuoli et al., 2010; Alexandrowicz, 2013) and in semi- arid (Brasil — Auler and Smart, 2001; Spain — Valero-Garcés et al., 2008; Luzón et al., 2011) and desert settings (Libya – Cremaschi et al., 2010; Ethiopia — Moeyersons et al., 2006). In the same way, the average air temperature is easily correlated to the extensive presence of forests that increased the supply of CO 2 in soils, thus enhancing the dissolution of carbonates and the saturation in calcite of karst waters after Sedimentary Geology 299 (2014) 60–73 ⁎ Corresponding author. Tel.: +39 0577 233856. E-mail addresses: martini.ivan@unisi.it, martinigeo@gmail.com (I. Martini). 0037-0738/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.sedgeo.2013.11.001 Contents lists available at ScienceDirect Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo