With few exceptions (Dupré 1988; Dupré et al. 1996; Davis 1994; Leroy 1990; 1997; 2008; Pérez-Obiol and Julià 1994; van der Knaap and van Leeuwen 1994; 1995), lake sediments from the Iberian Peninsula have been extensively explored for pollen only during the last decade (Burjachs et al. 1997; Carrión et al. 2001c; 2004b; Carrión 2002a; Muñoz-Sobrino et al. 2004; Valero-Garcés et al. 2006a; González-Sampériz et al. 2005; 2008; Morellón et al. 2008; Moreno et al. in press). In general, karstic lakes with permanent freshwater, and riverine wetlands and floodplains, are valuable for pollen analysis. But there are exceptions (Table 4). Pollen was absent in the less organic sediments of San Benito (Dupré et al. 1996) and Becorreiras (Santos et al. 2000; Santos 2004), and two metres of organic clay from Laguna de Orcera were fully barren, with characteristics similar to Siles (Carrión 2002a), Cañada de la Cruz (Carrión et al. 2001c), and El Sabinar (Carrión et al. 2004a), which had provided high-quality pollen data to reconstruct the past vegetation changes in the Segura Mountains since the Last Glacial Maximum (Carrión 2002a). In Sierra de Gádor (Almería), a 150cm-depth core of red clay from Balsa del Sabinar was completely sterile, while a darker, more organic, lacustrine deposit formed under more permanent-water conditions was evenly polliniferous (Carrión et al. 2003a).
Palaeo-lakes deserve special attention because they are sometimes associated with palaeontological and palaeoanthropological excavations. Considerable effort, involving up to five trials, has been put into the famous enclaves of the Guadix-Baza depression, without success (Gibert et al. 1988; Agustí and Julià 1990; Palmqvist et al. 2003) (Table 4). Repeated analyses probably resulted from the suggestion of an early Pleistocene (1.4-1.1 Ma) Eurasian colonisation by humans on the basis of local Oldowan and Acheulean lithics (Oms et al. 2000). Excavation sediments, although extremely rich in fauna, were also lacking pollen in the Plio-Pleistocene sites of Fonelas and Mencal, in the same basin. Sediments at these sites are very diverse including clays, silts and sands, occasionally exposing micrite limestone layers formed on the margins of palaeo-lacustrine depositional environments under low-energy water conditions (Arribas et al. 2004b). Other palaeolacustrine records, now in an exposed situation, have shown partially polliniferous results, such as Linás in Huesca, where Martí et al. (2002) and González-Sampériz et al. (2005) have identified evidence of selective pollen corrosion.
Saline lakes, widespread in endorheic depressions of inland Iberia (González-Beserán et al. 1991; Casado and Montes 1995) have also presented difficulties, especially when short-lived or seasonal (Table 4, Fig. 2). A notorious case study concerns the Pétrola, El Acequión and Ontalafia lakes in La Mancha Plain of south-central Spain. An international project (PB91-0897, MEC 1992-95) led by M. Dupré, University of Valencia (Table 2), had been specifically designed to link environmental and cultural changes during the Holocene, based on the pollen records expected from these lakes and archaeological reports from adjacent settlement sites (Nájera and Molina 1977; Jordán 1992). Deep sediment cores of 2900, 1010 and 1350cm were extracted from Pétrola, El Acequión, and Ontalafia, respectively. A total of 90 (Pétrola), 53 (Acequión), and 65 (Ontalafia) sediment samples were processed in the palynological laboratories of Valencia (MD) and Murcia (JC), but they all failed to show pollen.
Coastal salt marshes and lagoons, while equally problematic, represent a risk worth taking for pollen analysis (Table 1). A multi-core approach is appropriate here because pollen corrosion and sedimentary and palynological hiatuses may affect the deposit unevenly across the basin (Table 4). Successful cases come from the most arid parts of eastern Spain. Coastal salt marshes of San Rafael, Roquetas de Mar, and Antas (Almería) have yielded pollen records from pleniglacial to late Holocene times (Yll et al. 1994; Pantaleón-Cano et al. 2003). Northwards in Alicante, the Elx pollen sequence was also obtained from a lagoon (Burjachs et al. 2000). Pollen analyses of two coreholes in the Pego-Oliva littoral marsh were less rewarding. Pollen was scarce, poorly preserved, and episodically absent from quite an organic-rich, yet salty, shallow-sea sediment (Table 4).
Pollen analyses carried out in the Doñana marshlands (Abalario Estuaries Complex in the coastal arc of Huelva between the Guadalquivir and Tinto deltas) (Fig. 1) have produced contrasting results. In general, organic-rich layers are polliniferous (Table 4). Some marshy sediments have given pollen records, such as Las Madres (Stevenson 1985), El Acebrón (Stevenson and Moore 1988), Mari López (Yll et al. 2003), Laguna Redonda and Línea de la Mediana (Stevenson n.d.), and Las Nuevas. Other 'marisma' deposits have not been as rewarding, such as Carrizosa, Cherri, Juncabalejo, Membrillo, and Vetalengua (Yáñez 2005; Yáñez et al. 2006).
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Last updated: Mon Feb 23 2009