Mineralogical assemblages, geochemistry and fossil associations of Pleistocene–Holocene complex siliciclastic deposits from the Southwestern Doñana National Park (SW Spain): A palaeoenvironmental approach Manuel Pozo a, ⁎, Francisco Ruiz b , María Isabel Carretero c , Joaquín Rodríguez Vidal b , Luís Miguel Cáceres b , Manuel Abad b , María Luz González-Regalado b a Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, 28049-Madrid, Spain b Departamento de Geodinámica y Paleontología, Universidad de Huelva. Avda. Fuerzas Armadas, s/n. 21071-Huelva, Spain c Departamento de Cristalografía, Mineralogía y Química Agrícola, Universidad de Sevilla, Apdo. 553, Sevilla, Spain abstract article info Article history: Received 30 September 2009 Received in revised form 11 January 2010 Accepted 22 January 2010 Available online 1 February 2010 Communicated by M.R. Bennett Keywords: Estuarine environment Tsunami Quaternary Clay mineralogy Geochemistry On the basis of mineralogy, chemical and palaeontological data collected in a long core (93 m) three associations of facies are distinguished in the Late Pleistocene–Late Holocene evolution of the sedimentary infilling in nowadays Doñana National Park. From the lower, middle and upper associations of facies three sedimentological phases have been established. In the oldest phase (>44 kyr BP), this area was occupied by supratidal, freshwater marshes located close to a brackish lagoon and inundated suddenly by brackish- marine inputs. The following phase (44–7 kyr BP) is characterized by the transition from supratidal to intertidal conditions, with the alternation of freshwater or brackish marshes situated very close or in the margin of the former lagoon and submitted to episodes of desiccation or tidal inundation. The last phase (7–3.0 cal kyr BP) comprised: a) a marine inundation during the maximum of the Flandrian transgression (∼ 7–6.5 cal kyr BP); and b) the progressive infilling of a brackish lagoon with marine connection and permanent fresh water inputs (6.5–3.5 cal kyr BP), partially enclosed by the Doñana spit. The phyllosilicate-rich, clayey–silty sequence of this latter infilling is interrupted by tsunami-like deposits at 4.2–3.6 cal kyr BP and 3.6–3.0 cal kyr BP. These high-energy events are characterized by textural (bimodal grain-size distribution, sorting decrease), mineralogical (crystallochemical changes in illites, increasing dolomite content) and geochemical changes (Ti anomaly), besides a sudden introduction of marine bivalves and microfauna and a strong decrease or the almost disappearance of the brackish ostracode assemblage. Ages of these deposits coincide with those indicated for other tsunamigenic layers detected in the southwestern Spanish coasts and some deep cores collected near the African–European plate boundary. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The Pleistocene–Holocene evolution of estuaries, deltas, lagoons or the associated salt marshes have received an increasing attention in the last two decades (De la Vega et al., 2000; Edwards, 2001; Gerdes et al., 2003; Canali et al., 2007). The main palaeoenvironmental changes have been deduced from the multidisciplinary analysis of the geological record contained in several continuous cores. They include usually vertical lithostratigraphical, mineralogical and isotopic data as key tools to determine the origin and evolution of sediments, the variations of some physical–chemical water parameters or even palaeoclimatic oscillations (Chamley, 1989; Skrabal, 1991; Carretero et al., 2002; Reeves et al., 2007). The use of carbonate stable isotopes for the interpretation of depositional environments relies upon the characteristic of some chemical, biological and mechanical processes to fractionate stable isotopes as a result of the relative bond energies (Mason and Surdam, 1992). Moreover, the fractionation of δ 18 O is dependent upon the composition of the original waters and the depositional environment (Anderson and Arthur, 1983). Results derived from these investigations are contrasted with those derived from the palaeontological record in order to obtain either a detailed analysis of a short time interval or several successive palaeogeo- graphic reconstructions along a longer period (Grauert et al., 2001; Vött et al., 2006). In addition, several groups of microfossils (diatoms, foraminifers, ostracodes, calcareous nannoplankton, and pollen) have been used as tracers of the main palaeoenvironmental features (Cearreta et al., 2003; Fontana, 2005; Zong et al., 2006; Bao et al., 2007). The final interpretations can be improved if additional macrofossil groups are studied and the (palaeo-)autoecology of their main assemblages is taken into account (Hayward et al., 2002; Compton, 2007). Sedimentary Geology 225 (2010) 1–18 ⁎ Corresponding author. Tel.: +34 91 4974808. E-mail address: manuel.pozo@uam.es (M. Pozo). 0037-0738/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2010.01.002 Contents lists available at ScienceDirect Sedimentary Geology journal homepage: www.elsevier.com/locate/sedgeo