Javier García-Veigas CCiTUB, Universitat de Barcelona, 08028 Barcelona, Spain Gary R. Scott Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA * Corresponding author. E-mail address: lgibert@ub.edu (L. Gibert). © 2015 Elsevier Ltd. All rights reserved http://dx.doi.org/10.1016/j.quascirev.2015.01.014 A reassessment of the evidence for hydrothermal activity in the Neogene-Quaternary lacustrine environments of the Baza basin (Betic Cordillera, SE Spain) and its paleoecological implications 1. Introduction In a recent paper, García-Aguilar et al. (2014) reported on litho- logical, mineralogical and geochemical evidence of intense, tectonically-induced hydrothermal activity during the continental sedimentary infilling of the Baza basin, a postorogenic, intramon- tane area developed on the boundary between the Internal and External Zones of the Betic Cordillera, Southeast Spain (Fig. 1). This evidence includes the finding of sulfur contents, magnesium clays, fluorspar and celestine deposits, thermogene stromatolites and travertine growths in the latest Miocene (Turolian) to Middle Pleistocene lacustrine sediments and is particularly concentrated at certain stages and places (e.g. at Calabrian times in the Orce area). During the Calabrian, the climate was warmer and more stable (less seasonality) than nowadays in the Baza basin through the whole year, with precipitations that doubled those recorded today in the region, as inferred from the d 15 N values measured in the fos- sil collagen of large mammals (Palmqvist et al., 2008a, 2008b) and the presence of water-associated amphibians and reptiles (Blain et al., 2011). Together with the water supplies of the hot springs, this resulted in a lacustrine system not subject to periodic desicca- tions during the dry season. Such conditions allowed the presence of drought intolerant mammals and resulted in a high standing crop biomass of ungulates, which provided abundant carcasses to the scavenging hyenas and hominins (Espigares et al., 2013; Martínez-Navarro et al., 2014). The presence of these ‘ecological islands’ of hot waters helps to explain the high density of skeletal remains of large mammals preserved in the swampy/lacustrine sediments distributed along the lake surroundings (Arribas and Palmqvist, 1998). Tectonic activity has continued to the present and is responsible of more than one hundred hot springs that are nowadays active in the Betic Cordillera, most of them aligned with the major regional fractures in a N50  e70  E direction (Fig. 1A). These thermal waters, which show magnesium, sulfur and strontium anomalies, are asso- ciated to travertine buildings similar to those found in the Plio-Pleistocene deposits. For this reason, García-Aguilar et al. (2014) used the principle of actualismethe cornerstone of geology and paleontologyefor extrapolating to the past the relationship between tectonics and hot springs. However, Gibert et al. (2015) argue in this volume that geolog- ical evidence for hydrothermal activity in the saline lake system of the Baza basin is weak and offer in their Fig. 1 an alternative model that considers three interconnected sub-environments (inner, intermediate and marginal) for the whole interval of lacus- trine sedimentation (for a more in depth explanation of this model, see Gibert et al., 2007). In our opinion, this is not in agreement with the geology of the Baza basin and its tectono-sedimentary evolu- tion. In addition, they neither offer an alternative model of strati- graphic architecture for its continental infilling nor consider the role played by the faulting network on its sedimentary evolution during the Plio-Pleistocene (Sanz de Galdeano and Vera, 1992; Alfaro et al., 1997, 2010; García-Aguilar et al., 2014), including: (1) the tectonic activity evidenced by paleoseismites; (2) the tectonic control on the distribution in time and space of depositional envi- ronments and evidence of thermal activity; (3) the finding of organic-rich black levels in the lacustrine facies with high celestine contents, which are linked to zones of intense tectonic activity where the paleontological sites tend to be concentrated (e.g., the Late Villafranchian sites of Venta Micena, Fuente Nueva-3 and Barranco Le on); and (4) the current hydrothermal activity in the Baza basin, with 21 hot springs (Fig. 1B) that show water output temperatures of up to 38  C and high flow rates (e.g., 600 and 180 L s 1 in the spas of FuencalienteeHu escar and Ba~ nos de Zújar, respectively; Cruz-Sanjuli an et al., 1972). 2. Baza basin chronostratigraphy The model of interconnected sub-environments proposed by Gibert et al. (2015) as an alternative to our six lacustrine stages for the sedimentary infilling of the Baza basin is weakly supported, because it considers lateral changes in facies (e.g., marly-evaporitic sediments and carbonate deposits) between depositional environ- ments that did not coexist in time (Vera, 1970; García-Aguilar and Martín, 2000): sulphate-rich sedimentation is typical of the Gela- sian (García Aguilar et al., 2013) while carbonate-rich deposits char- acterize the Calabrian (García-Aguilar and Palmqvist, 2011) (Fig. 1B). For this reason, we think that their reinterpretation of the geochemical and mineralogical anomalies as “generated during the sedimentation and early diagenesis, in an evaporitic sedimen- tary environment fed by CaeHCO 3 -rich waters evolving to SO 4 - rich brines during evaporation” is wrong. Diagenetic phenomena could only explain these anomalies in a basin with a more static tectono-sedimentary context, which is not the case of the Baza ba- sin. In fact, magnesium clays, celestine, strontium and native sulfur do not distribute homogeneously in the lacustrine sediments, but are concentrated in areas placed in the vicinity of hot springs that are active today, or in zones that can be interpreted as hot springs active during the Plio-Pleistocene (Fig. 1B). Gibert et al. (2015) criticize that their paleomagnetic data were ignored in our chronostratigraphic framework for the lacustrine stages, which was based on the magnetostratigraphy of Garc es DOI of original article: http://dx.doi.org/10.1016/j.quascirev.2015.01.014. Correspondence / Quaternary Science Reviews 112 (2015) 226e235 230