Present-day and past (last 25 000 years) marine pollen signal off western Iberia

Marine Micropaleontology 62 (2007) 91 – 114 www.elsevier.com/locate/marmicro

Present-day and past (last 25 000 years) marine pollen signal off western Iberia F. Naughton a,e,⁎, M.F. Sanchez Goñi a,b , S. Desprat a,b , J.-L. Turon a , J. Duprat a , B. Malaizé a , C. Joli a , E. Cortijo c , T. Drago d , M.C. Freitas e a

c

Environnements et Paléoenvironnements Océaniques (UMR CNRS 5805 EPOC), Université Bordeaux 1, Av. des Facultés, 33405 Talence, France b Ecole Pratique des Hautes Etudes, Environnements et Paléoenvironnements Océaniques (UMR CNRS 5805 EPOC), Université Bordeaux 1, Av. des Facultés, 33405 Talence, France Laboratoire des Sciences du Climat et de l'Environnement (LSCE-Vallée), Bât. 12, avenue de la Terrasse, F-91198 Gif-sur-Yvette cedex, France d Centro Regional de Investigação Pesqueira do Sul , Instituto Nacional de Investigação Agrária e Pescas (INIAP) (IPIMAR-CRIPSUL), Av. 5 de Outubro, 8700-305 Olhão, Portugal e Departamento e Centro de Geologia-Universidade de Lisboa, Bloco C6, 3° piso, Campo Grande, 1749-016 Lisboa, Portugal Received 11 May 2006; received in revised form 17 July 2006; accepted 19 July 2006

Abstract The comparison between modern terrestrial and marine pollen signals in and off western Iberia shows that marine pollen assemblages give an integrated image of the regional vegetation colonising the adjacent continent. Present-day Mediterranean and Atlantic forest communities of Iberia are well discriminated by south and north marine pollen spectra, respectively. Results from Total Pollen Concentration together with recognized conceptual models of fine particle dynamics in the Iberian margin have allowed us to establish the present-day pattern of pollen dispersion in this region. The 25 000 year-long record of continental (pollen) and marine (δ18O of Globigerina bulloides, Ice-rafted detritus—IRD and Neogloboquadrina pachyderma s.) proxies, from the Galician margin composite core (MD99-2331 and MD03-2697), show that vegetation cover in north-western Iberia has responded contemporaneously to the climate variability of the North-Atlantic. The vegetation response to the well known North Atlantic Heinrich events 2 and 1 (H2 and H1) is however complex and characterised by two vegetation phases at low and mid-altitudes of north-western Iberia. The beginning of each Heinrich event is marked on land by an important pine forest reduction and the expansion of heathers which are synchronous with the heaviest planktic δ18O values and the maxima of N. pachyderma (s.) suggesting that these first phases were cold and wet. Pinus forest expansion characterising the second phase of each Heinrich event indicates a less cold episode associated, during H1, with an increase of dryness as suggested by the development of semi-desert associations. The comparison of our Galician margin multi-proxy record with several pollen sequences from in and off Iberia allows us to demonstrate that H1 event is the marine equivalent of the Oldest Dryas on the continent. The occurrence of temperate trees during the last glacial maximum (LGM) and the rapid expansion of deciduous Quercus during the Bölling-Allerød period in our Galician margin composite sequence show that not only the southern but also north-western Iberia was a refugium zone for deciduous trees during the last glacial period, especially at low and mid-altitude zones. Furthermore, the comparison between southern and northern marine and terrestrial sequences allows us to confirm that vegetation responded to the

⁎ Corresponding author. Environnements et Paléoenvironnements Océaniques (UMR CNRS 5805 EPOC), Université Bordeaux 1, Av. des Facultés, 33405 Talence, France. Tel.: +33 540008832; fax: +33 556840848. E-mail address: [email protected] (F. Naughton). 0377-8398/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.marmicro.2006.07.006

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Bölling-Allerød warming, the Younger Dryas cold event and the Holocene more quickly in low and mid-altitudes of north-western Iberia and in the south than in the high altitude northern region most likely as the result of the higher density of refugia for temperate trees in these zones during the LGM. © 2006 Elsevier B.V. All rights reserved. Keywords: Marine palynology; Pollen transport; Iberian margin; Heinrich events; LGM; Last glacial–interglacial transition

1. Introduction

2. Environmental setting

During the last decade several studies had been carried out in marine deep-sea cores off Iberia (Hooghiemstra et al., 1992; Sánchez Goñi et al., 1999, 2000, 2002, 2005; Boessenkool et al., 2001; Roucoux et al., 2001, 2005; Turon et al., 2003; Tzedakis et al., 2004; Desprat, 2005; Desprat et al., 2005, 2006, in press) to understand vegetation responses to the climate variability detected in the North Atlantic. Among these sequences, those covering the last 25 000 years show similar vegetation changes to those recorded by the available 25 000-year-long terrestrial records. However, no experimental studies have been conducted in order to demonstrate that pollen grains preserved in those marine sequences represent the regional vegetation of the nearby continent or to understand the mechanisms involved in the transport and dispersion of these grains from the continent to the sea. To fill these gaps, we have compared present-day continental (including coastal systems) pollen signatures with modern marine (including shelf and slope) pollen assemblages. We have also determined total pollen concentration (TPC) of those surface samples to recognize present-day patterns of pollen dispersion in the Iberian margin. Having assessed the reliability of the present-day pollen signal in the upper layer sediments of MD99-2331 deep-sea core, we will compare their 25 000-year highresolution pollen record with other marine and terrestrial pollen sequences (Pons and Reille, 1988; Hooghiemstra et al., 1992; Peñalba, 1994; Pérez-Obiol and Julià, 1994; Allen et al., 1996; Muñoz Sobrino et al., 1997, 2001, 2004; Peñalba et al., 1997; Von Engelbrechten, 1998; Combourieu Nebout et al., 1999, 2002; Sánchez Goñi and Hannon, 1999; Santos et al., 2000; Boessenkool et al., 2001; Roucoux et al., 2001, 2005; Gil García et al., 2002; Ruiz Zapata et al., 2002; Turon et al., 2003) to document accurately western Iberian vegetation changes over this period. Furthermore, the direct correlation between sea surface temperature and vegetation changes in and off Iberia from the multiproxy study of MD99-2331 and MD03-2697 deep-sea cores will allow us to link several well known terrestrial climate events with those detected elsewhere in the North Atlantic and over Greenland.

2.1. Study area and present-day vegetation and climate Western Iberia including Portugal and the north-western part of Spain extends from 37°N to 43°N and comprises essentially the Minho and Sado basins and the western part of the Douro and Tagus basins (Fig. 1). North-western Spain, including the Minho basin, is influenced by the wet, relatively cool and weakly seasonal Atlantic climate (annual precipitation mean: 900–1400 mm and temperature range: −7 to 10 °C) and is dominated by deciduous Quercus forest (Q. robur, Q. pyrenaica and Q. petraea), heath communities (Ericaceae and Calluna) and Ulex. There are also locally birch (Betula pubescens subsp. celtiberica) and hazel (Corylus avellana) groves, and brooms (Genista) (Alcara Ariza et al., 1987). In the south, the Tagus and Sado basins, influenced by Mediterranean climate (mean annual precipitation: 200–600 mm and temperature range: 4 to 14 °C), are dominated by evergreen sclerophyllous forests. Q. rotundifolia and Q. suber forests with Phillyrea angustifolia and Pistacia terebinthus colonise the western basins while Q. rotundifolia and Q. coccifera woodlands associated with Juniperus communis and Pinus halepensis occupies the eastern part. In the warmest zones, thermophilous elements such as Pistacia lentiscus and Olea sylvestris form the forests. Middle altitudes (700–1000 m a.s.l.) are dominated by deciduous Quercus forest (Q. pyrenaica and Q. faginea) associated with northern European species such as Taxus baccata. The degradation of this forest produces two types of brush communities: rockrose shrublands (Cistaceae) in zones with precipitation between 600 and 1000 mm and heath communities (Ericaceae) in wetter zones. Between both regions, there is a transitional zone which includes the hydrographic basin of the Douro. This zone is characterised by high precipitation values (700 to 1000 mm/year) and winter temperatures between 4 and − 4 °C. At high altitudes, the wettest and coldest zones reach 1600 mm/year and −8 °C, respectively (Polunin and Walters, 1985). The oceanic influence is particularly important in the northwest of the basin, where the Q. robur and Q. suber association

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Fig. 1. Study area. Dashed line divides the Atlantic and Mediterranean biogeographical zones (Walter, 1954 in Blanco Castro et al., 1997). White circles with a dark point represent the top samples analysed in this study; white circles represent the modern samples from the European Pollen Database; white circles with a cross represent the studied cores sites (MD03-2697 and MD99-2331); dark circles represent marine and terrestrial core sites used for comparison with our study. Continental sequences: (a) Square A locates sequences 1 to 5: (1) Laguna de la Roya (Allen et al., 1996), (2) Sanabria March (Allen et al., 1996), (3) Laguna de las Sanguijuelas (Muñoz Sobrino et al., 2004), (4) Lleguna (Muñoz Sobrino et al., 2004), (5) Pozo do Carballal (Muñoz Sobrino et al., 1997); (b) Sites 6 to 13 correspond to: (6) Laguna Lucenza (Santos et al., 2000); (7) Lagoa Lucenza (Muñoz Sobrino et al., 2001); (8) Lago de Ajo (Allen et al., 1996); (9) Los Tornos (Peñalba, 1994); (10) Saldropo (Peñalba, 1994); (11) Belate (Peñalba, 1994); (12) Atxuri (Peñalba, 1994); (13) Banyoles (Pérez-Obiol and Julià, 1994); (c) Square B includes sequences 14 to 19: (14) Quintanar de la Sierra (Peñalba et al., 1997); (15) Sierra de Neila–Quintanar de la Sierra (Ruiz Zapata et al., 2002); (16) Hoyos de Iregua (Gil García et al., 2002); (17) Laguna Masegosa (Von Engelbrechten, 1998); (18) Laguna Negra (Von Engelbrechten, 1998); (19) Las Pardillas lake (Sánchez Goñi and Hannon, 1999); (20) Padul (Pons and Reille, 1988); (21) Mougás (Gomez-Orellana et al., 1998); (22) Charco da Candieira (Van der Knaap and van Leeuwen, 1995). The marine cores represented on the map are: 8057 B (Hooghiemstra et al., 1992), SO75-6KL (Boessenkool et al., 2001), SU81-18 (Turon et al., 2003) and ODP 976 (Combourieu Nebout et al., 1999; 2002) and MD95-2039 (Roucoux et al., 2001; 2005).

predominates (Braun-Blanquet et al., 1956). The spread of both Pinus pinaster and Eucalyptus globulus has been favoured by anthropic impact. The understory vegetation is largely dominated by Ulex, in association with heaths. The river margins are colonised by Alnus glutinosa, Fraxinus angustifolia, Ulmus spp., Salix spp. and Populus spp. 2.2. Oceanography The western Iberian margin is dominated by the surface Portugal Current system (PCS) which is composed of the slow equatorward current in the open ocean

(Arhan et al., 1994) and the fast, seasonally reversing coastal current (Ambar and Fiúza, 1994; Barton, 1998) (Fig. 2). During the summer, the Azores high pressure cell is located in the central North Atlantic and the Greenland low is weak. This situation generates northerly and northwesterly prevailing winds (Fig. 1) which favour the occurrence of upwelling events and a southward surface circulation (Fiúza et al., 1982; Haynes and Barton, 1990) near the shelf break in the upper 50–100 m (Álvarez-Salgado et al., 2003). The resultant upwelled cold and nutrient-rich Eastern North Atlantic Central Water of subpolar sources (ENACWsp) is transported northward of 45°N. Warm, salty and nutrient-poor

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2.3. Morphology and recent sedimentation

2.3.1. North-western Iberian margin In north-western Iberia, five rivers (Douro, Ave, Cávado, Lima and Minho) release large amounts of sediments to the adjacent continental margin. The Douro is the main sediment supplier to the adjacent shelf (∼8.2 × 109 m3 annual mean discharge) followed by the Minho river (Dias et al., 2002; Jouanneau et al., 2002; Oliveira et al., 2002) (Fig. 3b). They are 927 km and 300 km long, draining a catchment area of 97 700 km2 and 17 100 km2, respectively (Loureiro et al., 1986). Above 42°N, rivers are replaced by rias (Vigo, Pontevedra, Arousa and Muros), which act essentially as sediment traps, preventing particle input to the adjacent margin (Dias et al., 2002; Jouanneau et al., 2002). The northern Portuguese continental shelf is composed of (a) an inner shelf zone (b30 m depth) with fine and well sorted sands, (b) a mid-shelf zone of coarse sands and gravels, and (c) a carbonate-rich outer shelf zone with medium sand (Van Weering et al., 2002). Within the shelf, there are two mud patches (Douro and Galicia) located offshore from the river inlets separated by a mud free zone (Lopez-Jamar et al., 1992) (Fig. 3b). The mud patch growth depends on the sediment supply, morphological barriers and hydrological conditions (Dias et al., 2002; Jouanneau et al., 2002). Sedimentation on the north-western Iberian margin is complex and essentially sustained by episodic flood events (Dias et al., 2002) and/or during maximal episodes of river outflow (Araújo et al., 1994; Drago et al., 1998). Fine

The Iberian margin is characterised by a relatively narrow shelf (30–50 km wide) with a steep irregular slope plunging to the oceanic abyssal plain (Fig. 3a). This margin is cut off by deep canyons like Mugia, Porto, Aveiro, Nazaré, Cascais, Lisbon, Setúbal and S. Vicente. The largest canyons (Nazaré, Setúbal) dissect the entire continental shelf, capturing sediments carried over the shelf and upper slope by alongshore currents, providing a direct conduit of particles from the upper shelf to the deep-sea (Vanney and Mougenot, 1981). Some canyons, e.g. Setúbal, start close by the presentday coastline and have a direct connection to the river mouth, while others, such as the Porto Canyon, begin only at the shelf edge and play a minor role in the interception of shelf material at the present-day sea level. All Iberian canyons were probably more active during the period of low sea-level (Van Weering and McCave, 2002). The lower and upper slopes are also intersected by several seamounts as Vigo (VS), Vasco da Gama (VDGS), Porto (PS), Tore (TS), by the Galicia Bank and several tectonic depressions (Vanney and Mougenot, 1981).

Fig. 2. West to east scheme of the different water masses from the western Iberian margin (adapted from Sprangers et al., 2004). White circles with a dark point represent southward water flow and white circle with a cross represent northward water flow. PCS—Portugal Current System; ENACW st—Eastern North Atlantic Central Water of subtropical origin; ENACW sp—Eastern North Atlantic Central Water of subpolar origin; MSW— Mediterranean Sea Water; LSW—Labrador Sea Water; NADW—North Atlantic Deep Water.

Eastern North Atlantic Central Water of subtropical origin (ENACWst) is transported to the south of 40°N (Fiúza, 1984; Rios et al., 1992) (Fig. 2). During the winter the Azores high pressure cell is located off the northwest African coast and the Greenland low is deep and situated off south-eastern Greenland. The pressure gradient between the two systems results in an onshore and slightly northward wind off Iberia (Fig. 1) triggering downwelling processes and a northward surface circulation (Frouin et al., 1990; Haynes and Barton, 1990). This reversion of hydrological paths starts in the end of summer in September–October and it persists until March–April representing the well known Portugal Coastal Counter Current (PCCC) (Ambar et al., 1986). This poleward flow is narrow (30 km wide) and it transports warm and salty waters (ENACWst) in the upper 200–300 m to the North (Pingree and Le Cann, 1990). Below the Central Waters system, between 550 m and 1500 m depth, the Mediterranean Sea Water (MSW) consisting of high salinity and relatively warm water mass is transported northward (Mazé et al., 1997) (Fig. 2). However, the salinity of the MSW decreases highly at latitudes higher than 41°N by mixing with the underlying low-salinity Labrador Sea water (LSW) (McCave and Hall, 2002). This LSW is one of the three water masses included in the North Atlantic Deep Water (NADW) over the western Iberian margin (Huthnance et al., 2002).

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sediments, after being released by rivers, are transported in nepheloid layers (Bottom—BNL, intermediate—INL and surface—SNL) to the outer shelf. Oliveira et al. (1999) have shown a seaward decrease of sediment concentrations in all nepheloid layers and that currents and waves induce resuspension of bottom sediments from Douro and Minho muddy deposits, especially during extreme storm events. During these extreme events, such as southwesterly storms (downwelling conditions), the spread of BNLs might be blocked by rocky outcrops (Drago et al., 1999) that operate as a barrier to cross-shelf transfers (Jouanneau et al., 2002; Van Weering et al., 2002) stimulating a poleward sediment transport (Drago et al., 1998; Dias et al., 2002; Jouanneau et al., 2002; Van Weering et al., 2002). Sporadically, waves associated with those storms are able to induce resuspension of fine deposits spreading offshore the BNL (Vitorino et al., 2002) nourishing the INL (Oliveira et al., 2002). These extreme events contribute to an important export of fine sediments (Vitorino et al., 2002) and occasionally of coarse fraction (Dias, 1987) to the upper slope. Current reversals, probably caused by the presence of local slope eddies, can also allow some down-slope transport of particles (Pingree and Le Cann, 1992). During upwelling conditions, fine sediment export is restricted to the shelf edge (McCave and Hall, 2002; Van Weering et al., 2002). However, lateral sediment exchange can be favoured by offshore filaments stretching westward (Huthnance et al., 2002). MD99-2331 and MD03-2697 twin deep-sea cores, located north-western of the Mesozoic and Cenozoic outcrops, mostly receive sediments coming from the Douro and Minho rivers, especially during downwelling conditions. 2.3.2. South-western Iberian margin In the south-western Iberian margin, the Tagus river is the primary sediment supplier followed by Sado river to the shore (Dias, 1987; Jouanneau et al., 1998) (Fig. 3a, c). The Tagus river is 1110 km long draining a catchment area of 80 600 km2 with 400 m3 s− 1 of annual mean flow (Vale, 1990). The Sado river is 175 km long, drains a catchment area of 7640 km2 and yields less than 10 m3 s− 1 of annual mean discharge (Loureiro et al., 1986). Differences between both river discharge and littoral currents influence the sediment distribution along the shelf (Jouanneau et al., 1998). The mud patch is located offshore of Tagus river basin and covers the entire continental shelf (Araújo et al., 2002). During summer, suspended particulate matter (SPM) concentration in the mouth of the Tagus estuary is four times higher than that of the Sado, and the nepheloid layer can extend 30 km westward (Jouanneau et al., 1998). Fine

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sediments are essentially exported to the slope and adjacent abyssal plains through the canyons of Cascais, Lisbon and Setúbal (Jouanneau et al., 1998) and by offshore filaments (Huthnance et al., 2002). 3. Material and methods 3.1. Deep-sea cores: MD99-2331 and MD03-2697 MD99-2331 (42°09′00N, 09°40′90W; 2110 m depth) and MD03-2697 (42°09′59N, 59°42′10W; 2164 m depth) deep-sea cores were retrieved in the Galician margin (northwest of Iberia) using a CALYPSO corer during the GINNA (IMAGES V) and PICABIA oceanographic cruises on board the R/V Marion Dufresne (Fig. 1). MD99-2331 and MD03-2697 are 37.2 m and 41.23 m long, respectively, covering Marine Isotopic Stages (MIS) 1 to 11. X-ray analysis using SCOPIX image-processing (Migeon et al., 1999) has shown a well preserved sedimentary sequence in core MD03-2697 while core MD99-2331 sees a sediment mixing zone between 1.10 m and 1.90 m of core depth. In order to obtain a detailed palaeoclimatic sequence for the last 25 000 years in and off NW Iberia, we have built a composite record assembling the MIS 1 interval of core MD03-2697 with the MIS 2 interval of core MD99-2331. 3.1.1. Radiometric dating Seven levels of MD03-2697 and twenty levels from MD99-2331 were dated by AMS 14C on Globigerina bulloides and Neogloboquadrina pachyderma (s.) at Beta Analytic Inc (Beta), at Gif-sur-Yvette (Gif) and at Laboratoire de Mesure du Carbone 14-Saclay (LMC), indicating that this sequence covers the last 25000 years (Table 1). All radiocarbon dates were corrected for marine age reservoir difference (400 years) (Bard et al., 2004). The samples presenting conventional AMS 14C younger than 21786 BP were calibrated by using CALIB Rev 5.0 program and “global” marine calibration data set (marine 04.14c) (Stuiver and Reimer, 1993; Hughen et al., 2004; Stuiver et al., 2005). We use 95.4% (2 sigma) confidence intervals and their relative areas under the probability curve as well as the median probability of the probability distribution (Telford et al., 2004). 14C radiometric ages older than 21786 years BP were calibrated by matching the obtained conventional AMS 14C with the calendar ages estimated for MD95-2042 deep-sea core by Bard et al. (2004). In this paper, we will use 14C ages (year BP) corrected for the marine reservoir effect (of 400 years) instead of calibrated ages (cal year BP) because in most of the Iberian terrestrial sequences, calendar ages are not available.

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Fig. 3. (a) Morphology of the Iberian margin. Location of the surface samples from (b) north-western Iberian margin and (c) south-western Iberian margin. White arrows indicate the present-day pattern of pollen dispersion in the western Iberian margin.

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3.1.2. Marine proxy analyses The planktic isotopic record of MD99-2331 covering MIS 6 to MIS 1 has been published in Gouzy et al. (2004). However, additional stable isotope measurements of planktic foraminifera have been done to refine the planktic isotopic record of the MIS 2 interval. In total, 56 measurements have been made at 2 to 10 cm sample resolution. For MIS 1, 29 levels with a sample spacing of 5 to 10 cm have been analysed in the MD03-2697 sequence. These measurements have been carried out on the 250–315 μm fraction of G. bulloides previously cleaned with distilled water. Each aliquot, including 8–10 specimens and representing a mean weight of 80 μg, was prepared in the Micromass Multiprep autosampler, using an individual acid attack for each sample. The CO2 gas extracted has been analysed against NBS 19 standard, taken as an international reference standard. Isotopic analysis of MD99-2331 has been carried out using an Optima Micromass mass spectrometer in the UMR CNRS 5805 EPOC (Environnements et Paléoenvironnements Océaniques) at Bordeaux 1 University and, those of MD03-2697 were performed using a delta plus Finnigan at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE). The mean external reproducibility of powdered carbonate standards is ±0.05‰ for oxygen. Results are presented versus PDB. Polar foraminifera, N. pachyderma (s.), counting include 79 levels (2 to 10 cm of sample spacing) and 40 levels (5 to 10 cm of sample spacing) from MD992331 and MD03-2697, respectively. IRD semiquantitative analysis has been carried out in 78 levels (2 to 10 cm sample spacing) and 30 levels (5 to 10 cm sample spacing) from MD99-2331 and MD03-2697, respectively. In this study, only the total concentrations of the lithic grains were considered. Both analyses were performed on the N 150 μm sand-size fraction which was obtained according to classic sedimentological procedure. 3.1.3. Pollen analysis 110 and 22 samples with a sample spacing of 2 to 10 cm and 5 to 10 cm were analysed from MD99-2331 and MD03-2697, respectively. In each 1 cm-thickness sample, 3 to 5 cm3 of sediment were treated for pollen analysis. The treatment of the samples from both deep-sea cores (MD99-2331 and MD03-2697) followed the procedure described by de Vernal et al. (1996), slightly modified at the UMR CNRS 5805 EPOC (Desprat, 2005). Palynological treatment consists of pollen concentration by chemical digestion using cold HCl (at 10%, 25% and 50%) and cold HF (at 40% and 70%) to eliminate carbonates and silicates, respectively. A Lycopodium spike of known concentration has been added to each

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sample to calculate total pollen (including spores) concentrations. The residue was sieved through a 10 μm nylon mesh screen (Heusser and Stock, 1984) and mounted in bidistillate glycerine. A Zeiss microscope with ×550 and × 1250 (oil immersion) magnifications was used for pollen observation and counting. Pollen identifications were achieved via comparison with specialised atlases (Moore et al., 1991; Reille, 1992) together with the pollen reference collection of the UMR CNRS 5805 EPOC. At least 100 pollen grains (excluding Pinus, aquatic plants and spores) and 20 pollen types were counted in each of the 142 samples (deep-sea cores and modern samples, cf. Section 3.2.) analysed to obtain statistically reliable pollen spectra (McAndrew and King, 1976). Pollen percentages were calculated based on the main pollen sum which excludes aquatic plants, spores, indeterminate and unknown pollen grains. Because Pinus grains are usually overrepresented in marine sediments (Heusser and Balsam, 1977), they are also excluded from the main sum and their percentages are determined by using the total sum (pollen + spores + indeterminable + unknowns). 3.2. Modern pollen samples We have analysed the pollen grains of 10 top samples from several estuarine, shelf and marine sedimentary sequences retrieved in and off western Iberia (Fig. 1, Table 2). The high percentages of Pinus detected in these top samples confirm that they represent the last 0–350 years, since it is well known that Pinus reforestation in western Iberia started in the seventeenth century (Valdès and Gil Sanchez, 2001). Because major vegetation changes are not detected in percentage pollen diagrams for the last centuries in this region (Desprat et al., 2003), we assume that our modern samples represent present-day pollen signatures. The resulting marine and coastal modern pollen assemblages have been compared with 12 terrestrial pollen samples including moss samples, surface sediments and top of peat bog and lake sequences, of both the Mediterranean and Atlantic parts of western Iberia stored in the European Pollen Database, http://www.imep-cnrs.com/pages/EPD. htm, (Peyron et al., 1998; Barboni et al., 2004) (Fig. 1). 4. Results and discussion 4.1. Present-day pollen signature 4.1.1. Western Iberian terrestrial sites Fig. 4 shows pollen spectra from several modern samples collected in western Iberian Peninsula. Pollen

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Table 1 Radiocarbon ages of MD99-2331 and MD03-2697 deep-sea cores Lab code

Core–depth (cm)

Material

Conventional AMS 14C age BP

Conv. AMS 14C age BP (− 400 years)

Error

95.4% (2σ) cal BP age ranges

Cal BP age median probability

Beta-2131134 Beta-2131135 Beta-003257 Beta-2131136 Beta-2131137 Beta-003258 Beta-003259 LMC14-001231 LMC14-001232 GIF-102377 LMC14-001233 LMC14-001235 LMC14-001236 LMC14-001237 LMC14-002445 GIF-101109 GIF-102373 LMC14-002446 LMC14-001845 LMC14-001846 LMC14-001847 LMC14-001849 LMC14-001850 GIF-102378 LMC14-001851 LMC14-001852 LMC14-001853

MD03 2697-20 MD03 2697-40 MD03 2697-70 MD03 2697-80 MD03 2697-110 MD03 2697-150 MD03 2697-200 MD99 2331-200 MD99 2331-205 MD99 2331-220 MD99 2331-222 MD99 2331-228 MD99 2331-235 MD99 2331-242 MD99 2331-260 MD99 2331-290 MD99 2331-570 MD99 2331-590 MD99 2331-595 MD99 2331-600 MD99 2331-607 MD99 2331-620 MD99 2331-623 MD99 2331-630 MD99 2331-637 MD99 2331-650 MD99 2331-655

G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides N. pachyderma N. pachyderma N. pachyderma N. pachyderma N. pachyderma N. pachyderma N. pachyderma G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides G. bulloides N. pachyderma G. bulloides G. bulloides G. bulloides

2880 4760 7435 7470 9940 11 920 12 520 13 640 13 810 14 130 13 920 13 930 15 130 15 060 15 540 16 170 19 770 22 290 20 860 20 550 20 460 21 620 21 740 22 690 22 150 22 440 22 430

2480 4360 7035 7070 9540 11 520 12 120 13 240 13 410 13 730 13 520 13 530 14 730 14 660 15 140 15 770 19 370 21 890 20 460 20 150 20 060 21 220 21 340 22 290 21 750 22 040 22 030

40 40 50 40 40 60 60 80 80 120 90 80 90 90 90 130 170 170 250 240 140 160 160 180 170 170 180

2501:2739 4866:5198 7783:7998 7835:8014 10 705:11 084 13 233:13 486 13 816:14 111 15 303:16 099 15 524:16 359 15 898:16 828 15 658:16 520a 15 686:16 521a 17 250:18 182 17 170:18 038 18 405:18 723 18 787:19 265 22 534:23 622 ∼ 25,950b, c 23 931:25 369 23 450:24 803 23 652:24 405 25 301:26 000 25 439:26 000 ∼ 26 350b,c ∼ 25 800c ∼ 26 000c ∼ 26 000c

2656 5008 7895 7930 10 896 13 353 13 965 15 679 15 922 16 342 16 067a 16 081a 17 848 17 722 18 520 18 983 23 038 ∼ 25 950b,c 24 542 24 119 24 016 25 626 25 730 ∼ 26350b,c ∼ 25 800c ∼ 26 000c ∼ 26 000c

a b c

Not acceptable dating (bioturbated layers). Radiocarbon dates too old (not used). Dates calibrated by matching conventional AMS 14C with calendar ages estimated for MD95-2042 deep-sea core by Bard et al. (2004).

assemblages from surface samples located above 42°N (COV1, MUN1, MUN3, ES09, E258 and ES62), record the Atlantic deciduous forest (Figs. 1 and 4). However, the dominant tree species differs from place to place reflecting the heterogeneity of the vegetation cover of this region (Fig. 4). For example, deciduous Quercus is the most important tree pollen in samples ES09, ES258, MUN3 and ES62 while Corylus dominates COV1 pollen spectrum and Betula that of MUN1. The pollen signal from the southern samples (FRA1, FRA4, GAT1, EXT1 and EXT2) represents Mediterranean plant communities, essentially composed of evergreen Quercus (Quercus ilex-type) and Olea (Figs. 1 and 4). However, FRA4 sample also includes relatively high percentages of pollen of deciduous trees, similar to those found in pollen spectra from north-western Iberia. This sample, though located in the Mediterranean region, comes from a high altitude deciduous oak forest zone. Within this southern region, sample ESO6 collected in the coastal area reflects open vegetation resulting of saline conditions and sandy soils,

preventing the development of deciduous and perennial forests. These southern samples also reflect the mosaic of the vegetation colonising present-day southern Iberia. We notice that, the southern pollen samples show higher percentages of Mediterranean plants than the north-western Iberian samples (Fig. 4), clearly discriminating between Mediterranean and Atlantic plant community sources, respectively. 4.1.2. Western Iberian estuarine and margin sites Estuarine pollen samples VIR-18 (Ría de Vigo) and Laquasup (Douro estuary), are marked by relatively high percentages of deciduous forest reflecting the present-day vegetation of north-western Iberia (Figs. 1 and 5). Shelf and slope samples (MD99-2331, CG11, Po 287-13-2G and MD04-2814 CQ), located in the adjacent margin, reproduce the same pollen signal as that of these northern estuarine samples. Southern samples from estuarine (Barreiro) and margin (MD992332, FP8-1 and MD95-2042) sites present in turn

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

higher percentages of Mediterranean plants than northern sites (Fig. 5). As in terrestrial samples, Mediterranean and Atlantic plant communities are well discriminated in the pollen signal from estuarine and margin sites (Figs. 1 and 5). It is important to note that the estuarine pollen assemblages are more similar to the marine ones than to the terrestrial pollen spectra. Indeed, estuarine sediments contain pollen from the regional vegetation which colonises the hydrographic basin while terrestrial samples mainly reflect local vegetation (Figs. 4 and 5). This indicates, as previous studies have already shown for the south-western French margin (Turon, 1984), that pollen spectra off north-western Iberia reflect an integrated image of the regional vegetation of the adjacent continent. Pinus percentages from western Iberian samples are relatively low when compared with estuarine, shelf and slope samples off this region (Fig. 5). This is in agreement with the observed overrepresentation of Pinus pollen in marine sediments in general and, in particular, off south-western Europe (Turon, 1984). Other works have further shown that Pinus pollen percentages increase seawards (Heusser and Balsam, 1977; Heusser and Shackleton, 1979). Our study confirms this pattern in the north and south-western margins. However, MD95-2042 site, representing the farthest sample from the coast line, presents weaker percentages of Pinus pollen than estuarine and the other marine samples. Despite the general Pinus overrepresentation in marine sediments, the good correlation between both terrestrial and marine present-day pollen signatures in and off western Iberia confirm the reliability of past vegetation and climate change reconstructions of this region proposed by previous works on western Iberian margin cores (Hooghiemstra et al., 1992; Sánchez Goñi et al., 1999, 2000, 2002, 2005; Boessenkool et al., 2001; Roucoux et al., 2001, 2005; Turon et al., 2003; Tzedakis et al., 2004; Desprat et al., 2005, 2006, in press).

99

4.2. Present-day pollen transport patterns Previous works on coastal zones with complex fluvial systems have shown that pollen is mainly transported to the sea by rivers and streams (Muller, 1959; Bottema and van Straaten, 1966; Peck, 1973; Heusser and Balsam, 1977). The western Iberian margin, close to several important hydrographic basins such as Tagus and Sado in the south and Douro and Minho in the north, mainly receives pollen through fluvial transport (Fig. 3). Furthermore, north-western prevailing winds in both north and southern regions probably impede substantial direct airborne transport of pollen seaward. This pattern of fluvial transport contrasts with others, e.g. north-western Africa, associated with an arid environment, where pollen grains are mainly seaward transported by the wind (Dupont et al., 2000; Hooghiemstra et al., 2006). Indeed, the distribution of the TPC shows (Fig. 5) that the highest TPC values are found in samples from coastal areas such as the Douro estuary (Laquasup: 44399 × 103 grains/cm3) and the Ría de Vigo (VIR-18: 65443 × 103 grains/cm3). Barreiro sample is an exceptional case with low TPC (18× 103 grains/cm3) probably because it was collected far away from the Tagus main channel and likely receiving pollen only from the local vegetation. Shelf surface samples present intermediate concentration values (CG11: 30468 × 103 grains/cm3, Po 287-13-2G: 42 600× 103 grains/cm3 and MD99-32b: 56 396 ×103 grains/cm3) and finally slope samples attain the lowest TPC values (MD99-2331: 1924 ×103 grains/ cm3, MD04-2814 CQ: 1886 ×103 grains/cm3, MD952042: 2153 ×103 grains/cm3 and IFP8: 3489× 103 grains/ cm3). Our work shows that a seaward decrease of total pollen concentrations occurs on the Iberian margin following the estuary-shelf-slope transect (Fig. 3). This pattern coincides with that observed in other margin zones around the world showing a seaward decrease in total pollen concentration with maximum values close to the mouth of the river systems (Muller, 1959; Bottema and van Straaten,

Table 2 Location, water depth and year of sample sampling from coastal, shelf and slope sequences of the Iberian margin Sample name

Depth (cm)

Latitude

Longitude

Water depth (m)

Year of sampling

MD95-2042 1FP8-1 MD99-2332 Barreiro MD04-2814 CQ Laquasup Po 287-13-2G CG11 MD99-2331 Vir-18

Top (0–1) Top (0–1) Top (0–1) Top (0–1) Top (0–1) Top (0–5) Top (0–1) Top (0–1) 3–4 Top (0–1)

37°48′N 38°01′N 38°33′N 38°40′N 40°37′N 41°09′N 41°09′N 41°48′N 42°09′N 42°14′N

10°10′W 09°20′W 09°22′W 09°07′W 09°52′W 08°38′W 09°01′W 09°04′W 09°42′W 08°47′W

3148 980 97 0 2449 0 81 107 2120 45

1995 2003 1999 1999 2004 2001 2002 1992 1999 1990

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1966; Cross et al., 1966; Groot and Groot, 1966, 1971; Koreneva, 1966; Stanley, 1966; Mudie, 1982; Turon, 1984; Van der Kaars and de Deckker, 2003). Based on several studies of sedimentary dynamics on the north-western Iberian margin (Araújo et al., 1994; Drago et al., 1998; Dias et al., 2002; Huthnance et al., 2002; Jouanneau et al., 2002; Oliveira et al., 2002; Van Weering et al., 2002; Vitorino et al., 2002), we propose a pattern of pollen dispersion for this region (Fig. 3b). This pattern is similar to the distribution model of fine terrigenous particles proposed by Dias et al. (2002). Pollen and spores, once immersed behave in a similar manner to fine sedimentary particles (Chmura and Eisma, 1995). After being released by rivers (mainly Douro followed by Minho), pollen grains, are enclosed in nepheloid layers and transported to the shelf until getting blocked by the rocky outcrops. In winter, during downwelling conditions pollen grains are then transported polewards, firstly deposited in the Douro mud patch (S–N direction) then in the Galicia mud patch, and finally they flow westward to the deep-sea. Only small quantities of pollen grains can be transported directly to the outer shelf and upper slope under extreme stormy events. In summer, under upwelling conditions, pollen transfer to the slope must be restricted to offshore filaments as suggested by Huthnance et al. (2002) for the fine sediments. In the southern Iberian margin, TPC values also decrease seawards as in the northern region (Fig. 5). Our study suggests that pollen grains released by the Tagus and to a lesser extent by the Sado river, are partially deposited in the shelf and transported to the south and seaward by littoral and oceanic currents probably during upwelling conditions (Fig. 3c). Pollen grains are probably transported by the southern canyons from the shelf to the slope and abyssal plain following the fine particle pathway suggested by several works on sedimentary dynamics in this region (Dias, 1987; Jouanneau et al., 1998; Araújo et al., 2002). 4.3. Climatic and vegetational response in western Iberia to North Atlantic climatic events over the last 25 000 years The comparison of the high resolution pollen composite record from the Galician margin (Fig. 6; Table 3), with other marine and terrestrial pollen sequences

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(Figs. 1 and 7; Tables 4 and 5) document the vegetation changes that occurred in the Iberian Peninsula over the last 25 000 years. Moreover, the direct correlation between marine proxies and vegetation changes from this record will allow us to accurately evaluate the vegetation response to the climatic events detected elsewhere in the North Atlantic Ocean and over Greenland. 4.3.1. Marine isotopic stage 2 4.3.1.1. Heinrich events (H2 and H1). Our Galician margin composite record reveals two periods marked by the dominance of herbaceous communities (Poaceae, Ericaceae, Calluna, Cyperaceae, Aster-type, Taraxacum-type) along with a Pinus forest reduction indicating two major cold events in north-western Iberia. These events, pollen zones MD31-2-2 and MD31-2-4, are centred at around 21 700 years BP and 14 700 years BP, respectively. In the ocean, our record identifies H2 and H1 events on the basis of, as usual in other North Atlantic cores, peaks in ice rafted detritus (IRD), high polar foraminifera (N. pachyderma s.) percentages and heavy planktic δ18O values (e.g., Heinrich, 1988; Bond et al., 1993; Duplessy et al., 1993; Grousset et al., 1993; Bond and Lotti, 1995; Lebreiro et al., 1996; Baas et al., 1997; Abrantes et al., 1998; Cayre et al., 1999; Bard et al., 2000; Shackleton et al., 2000; Thouveny et al., 2000; Broecker and Hemming, 2001; de Abreu et al., 2003; Hemming, 2004). Radiocarbon ages obtained for H2 (∼ 22 000 to ∼ 20 000 years BP) and H1 (∼ 15 350 to ∼ 13 000 years BP) intervals in our Galician margin record are in agreement with the age limits of these events, proposed by Elliot et al. (1998) for the North Atlantic. Direct correlation between pollen and marine proxies performed in this record (Fig. 6; Table 3) shows that these major cold events in north-western Iberia are only associated with the first part of H2 and H1. Indeed, H2 and H1 encompass two vegetational phases. Besides the Pinus forest contraction, the first part of H2 (∼ 22 000 to 21 500 years BP; MD31-2-2 pollen zone) and H1 (∼ 15 350 to 14 500 years BP; MD31-2-4 pollen zone) is characterised by the expansion of Calluna. Calluna vulgaris is a light demanding species (Calvo et al., 2002) favoured by forest regression and moist conditions. This indicates that the first part of both Heinrich

Fig. 4. Pollen spectra from western Iberian modern samples. Total temperate and humid (Tot. Temp./Hum.) trees include: Alnus, Betula, Corylus, deciduous Quercus and other temperate and humid species (Acer, Fagus, Fraxinus, Salix, Tilia, Ulmus, Hedera helix, Myrica and Vitis). Total Mediterranean (Tot. Mediter.) plants include: evergreen Quercus, Olea and Cistus. Taraxacum-type, Asteraceae, Poaceae, Ericaceae and Calluna represent the ubiquist group. Semi-desert plants include Ephedra, Chenopodiaceae and Artemisia. Climate parameters: Alt: altitude; PP: precipitation; MTCO: mean temperature of the coldest month; MTWA: mean temperature of the warmest month; TANN: annual temperature.

102 F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

Fig. 5. Pollen assemblages of top samples from coastal and marine western Iberian sites (see also caption of Fig. 4). TPC: total pollen concentration.

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114 Fig. 6. Galician margin composite record (MD99-2331 and MD03-2697 deep-sea cores). From the left to the right: corrected radiocarbon ages; marine proxies: δ18O of G. bulloides, % N. pachyderma (s.), ice-rafted detritus (IRD), Marine and Greenland climatic events; % pollen taxa; pollen zones and chronostratigraphy. Pollen zones were established using qualitative and quantitative fluctuations of a minimum of 2 curves of ecologically important taxa (Pons and Reille, 1986). They are defined by the abbreviated name of the core (MD31 or MD97) followed by the number of the marine isotopic stage (1 or 2) and numbered from the bottom to the top (MD31-2-1 to MD31-2-5 and MD97-1-1 to MD97-1-6).

103

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events was cold and humid. Furthermore, the first part of H1 is marked by the continuous presence of the Isoetes fern suggesting also moist conditions.

The second part of H2 (21 500 to 20 000 years BP; first 1500 years of the MD31-2-3 pollen zone) and that of H1 (14 500 to 13 000 years BP, MD31-2-5) are

Table 3 Description of the pollen zones in the Galician margin composite core and respective chronostratigraphy Pollen zones

Pollen signature

MD97-1-6

Strong increase of Pinus (15–70%) Holocene Continuous decrease of deciduous Quercus Ericaceae (55%), Poaceae (10%) and Taraxacum-type (10%) Continuous decline of Pinus (40–15%), deciduous Quercus (40–15%), Corylus and evergreen Quercus, presence of Alnus (8–12%) Ericaceae increase (30–55%) Gradual decline of Pinus (60–40%) and deciduous Quercus (60–40%), maximum expansion of Corylus (6–10%), beginning of Alnus continuous presence Gradual increase of Ericaceae (10–30%) and decrease of herbaceous pollen percentages: Poaceae (b10%), Calluna (b2%), Aster-type (b1%) and Cyperaceae (b2%) Semi-desert (b3%) Spores presence (pislete triletes and Isoetes) Pinus decline (∼ 60%) Maximum expansion of deciduous Quercus (60–80%), beginning of Corylus continuous presence, presence of evergreen Quercus Herbaceous pollen percentages decrease: Ericaceae (b10%), Poaceae (b10%), Calluna (b2%), Aster-type (b1%) and Cyperaceae (b2%) Semi-desert (b3%)

MD97-1-5

MD97-1-4

MD97-1-3

Chronostratigraphy

MD97-1-2

Pinus (80–90%) Decrease of deciduous Quercus (40%) and increase of Betula (10%) Poaceae increase (20–30%), Ericaceae (10–20%), Taraxacum-type (b10%) Increase of semi-desert associations: Artemisia (∼ 5–15%), Chenopodiaceae (∼ 3%), Ephedra (∼ 2%)

MD97-1-1

Pinus (80–90%) BöllingStrong increase of tree percentages: deciduous Quercus (40–60%) Allerød (B-A) Decrease of ubiquist associations: Poaceae (10–20%), Ericaceae (b20%), Cyperaceae (∼ 10%); Calluna (b5%) Presence of pioneer species: Betula, Cupressaceae and Hippophae

MD31-2-5

Pinus (∼ 80%) Oldest Dryas Poaceae (30%), Ericaceae (10–15%), Calluna (b10%), Cyperaceae (5–10%), Aster-type (∼ 10%), Taraxacum-type (∼ 10%) Semi-desert associations: Artemisia (2–12%), Chenopodiaceae (∼ 3%), Ephedra (b2%) Presence of pioneer species (Betula and Hippophae) (b5–10%) Strong decrease of Pinus (∼ 20–40%) Poaceae (20–45%), Ericaceae (∼ 20%), Calluna (10–20%), Cyperaceae (b10%), Aster-type (10–20%), Taraxacum-type (15–20%) Semi-desert associations: Artemisia (b5%), Chenopodiaceae (b5%), Ephedra (∼2%)

MD31-2-4

MD31-2-3

MD31-2-2

MD31-2-1

Younger Dryas (YD)

Pinus (∼ 60%) Late Poaceae (20–40%), Ericaceae (20–45%), Calluna (2–15%), Cyperaceae (5–10%), Aster-type (2–15%), Pleniglacial Taraxacum-type (5–30%) Semi-desert associations: Artemisia (b5%), Chenopodiaceae (b3%), Ephedra (b2%) Presence of temperate trees (b5–10%) and pioneer species Pinus (30–40%) Poaceae (20–40%), Ericaceae (20–30%), Taraxacum-type (10–20%), Calluna (15–20%), Aster-type (10%) Semi-desert associations: Artemisia (b5%), Chenopodiaceae (1–2%) Pinus (∼ 60%) Poaceae (0–20%), Ericaceae (20–30%), Calluna (10%), Cyperaceae (5–10%), Aster-type (b10%), Taraxacum-type (10–20%) Semi-desert associations: Artemisia (1–5%), Chenopodiaceae (0–3%), Ephedra (b2%)

Late Glacial period

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

105

Fig. 7. Comparison between continental (Quintanar de la Sierra; Peñalba et al., 1997) and marine (MD99-2331 and MD03-2697) pollen sequences.

106

Table 4 Description of pollen zones from the well-dated reference sites of Quintanar de la Sierra (Peñalba, 1994; Peñalba et al., 1997), Laguna de la Roya (Allen et al., 1996) and Padul (Pons and Reille, 1988) Years 14 C BP/continental sequences

1200–present day

6000–3000

Quintanar de la Sierra (1470 m a.s.l.) (Peñalba, 1994; Peñalba et al., 1997)

Padul (785 m a.s.l.) (Pons and Reille, 1988)

year BP

year BP

year BP

Local increase of Betula (30–50%) Poaceae (20–30%), Ericaceae (5–10%), Rumex (∼2%) Culture presence: Olea, Castanea and Cerealia Absence of Pinus and Quercus decrease Poaceae (30–40%) well represented, spread of Ericaceae (10%) Decrease of Pinus, Betula and slight decrease of Quercus Succession of Juniperus, Betula, Quercus, Corylus and 3060 Alnus

10 000–8200 Younger Dryas

10 290 Pinus presence (10–40%) Poaceae (20–30%), Artemisia (10%), Chenopodiaceae, Plantago, Caryophyllaceae, Anthemis-type and Calluna)

Late Glacial interstadial

Succession of Juniperus, Betula, Quercus Pinus well represented (40–60%) Late Glacial (Q S and LR)/ 12 940 Pinus presence (10–30%) Poaceae (20–40%) , Artemisia (20–40%), Oldest Dryas (Padul) Chenopodiaceae (2–5%), Plantago (∼2%), Caryophyllaceae (2%), Aster-type (2%) and Calluna (2%)

Late Pleniglacial

Pinus, Fagus and herbs (Ericaceae, Cerealia)

–

Spread of Fagus

–

Spread of Corylus

4450

Maximum percentages of trees (Betula, Pinus, deciduous Quercus, Quercus ilex and Corylus) 8200 Succession of Juniperus, Betula 8200 and deciduous Quercus and Quercus ilex 10 120 Pinus presence (20–40%) 10 000 Poaceae (20–30%), Artemisia (10%), Apiaceae (10–15%), Plantago (5%), Aster (2%), Cyperaceae (2–10%), Chenopodiaceae and Calluna 11 050 Succession of Juniperus, Salix, Betula Pinus well represented (60–80%) 13 350 Pinus presence (10–15%) Poaceae (20–40%), Artemisia (15–30%), 13 200 Chenopodiaceae (∼5%), Plantago (0–7%), Cyperaceae (5–10%), Aster (2–5%)

–

–

–

–

Deciduous Quercus, Quercus ilex, Quercus suber, Pistacia Pinus is almost absent (b5%)

Deciduous Quercus, Quercus ilex, Pistacia Pinus is almost absent (b5%) Decrease of trees until 40% Artemisia (N10%), Poaceae (20%), Chenopodiaceae (N10%), Ephedra (5%), Cyperaceae (20–30%) Slight increase of Pinus Juniperus, Betula, deciduous Quercus, Quercus ilex and Pistacia Pinus decrease (b 40%) Artemisia (20%), Poaceae (20–40%), Chenopodiaceae (N10%), Cyperaceae (60–100%)

15 200 Pinus increase (50–75%) Artemisia (10–20%), Poaceae (10%), Chenopodiaceae (b10%), Cyperaceae (0–30%). Presence of trees (5%) 19 800 Alternation of coldest episodes: Artemisia (30–60%), Chenopodiaceae (10%), Cyperaceae (b 20%), Poaceae (b 10%) and Pinus presence (10–20%) with less cold episodes: Artemisia (10–20%), Chenopodiaceae (b5%), Cyperaceae (50–80%) 23 600 Poaceae (20%) and Pinus increase (50–70%)

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

3000–1200

Laguna de la Roya (1608 m a.s.l.) (Allen et al., 1996)

Table 5 Holocene tree succession in north-western Iberia Lagunade La Roya (42°6′N, 6°44′W) 1085 m a.s.l.

Lago de Ajo (43°3′N, 6°9′W) 1570 m a.s.l.

Laguna Masegosa (42°57′N, 2°49′W) 1600 m a.s.l.

Laguna Negra (42°0′N, 2°52′W) 1760 m a.s.l.

Banyoles Lake (42°08′N, 2°45′E) 173 m a.s.l.

Las Pardillas Lake (42°2′N, 3°2′W) 1850 m a.s.l.

Laguna Lucenza (Sierra de Queixa) (Galicia) 1420 m a.s.l.

Hoyos de Iregua (42°01′N, 2°45′W) 1780 m a.s.l.

Pozo do Carballal (42°42′N, 7°07′W) 1330 m a.s.l.

Lagoa Lucenza (42°35′N, 7°07′W) 1375 m a.s.l.

Laguna Holocene de las sub-phases Sanguijuelas (42°08′N, 6°42′W) 1080 m a.s.l.

Pinus

Betula

Betula

Pinus

Pinus

Pinus

Pinus

Betula

Pinus

Betula

Betula

Fagus

Fagus

Fagus

Fagus

Fagus

Fagus

Abies

Fagus

Salix

Fagus

Fagus

Late Holocene 5000– 4000–3000 years BP until present day

Taxus Corylus

Taxus Alnus

Ulmus

Alnus

Taxus Alnus

Alnus

Alnus

Alnus

Alnus

Alnus

Fraxinus

Ulmus

Ulmus Fraxinus Corylus

Alnus Fraxinus Corylus

Ulmus Taxus Fraxinus

Ulmus Fraxinus Corylus

Corylus

Ulmus Fraxinus Corylus

Ulmus Corylus

Salix Corylus

Ulmus Corylus

Alnus Ulmus Corylus

Alnus Fraxinus Corylus

MidHolocene 9000–8000 years BP to 5000–4000 years BP

Dec. Quercus

Quercus

Betula Juniperus

Eve. Eve. Quercus Quercus Dec. Quercus Dec. Quercus Pinus Acer Salix Betula Betula Pinus Juniperus Juniperus

Eve. Quercus Dec. Quercus Salix Betula Pinus Juniperus

Dec. Quercus

Betula Juniperus

Corylus Eve. Quercus Dec. Quercus Pinus Salix Betula Juniperus

Eve. Quercus Dec. Quercus Pinus Betula

Eve. Quercus Dec. Quercus Salix Betula Juniperus Pinus

Eve. Quercus Dec. Quercus Betula Pinus Juniperus

Eve. Quercus Dec. Quercus Salix Juniperus Pinus Betula

Eve. Quercus Dec. Quercus Pinus Salix Betula Juniperus

Salix Betula Pinus

Early Holocene 10 500 years BP to 9000–8000 years BP

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Quintanar de la Sierra (42°02′N,3°W) 1608 m a.s.l.

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marked by a Pinus expansion, indicating less cold conditions than the previous phases. Furthermore, during the second part of H1, a gradual increase of semi-desert plants (Artemisia, Chenopodiaceae and Ephedra) reflects a gradual dryness on land. Our multiproxy palaeoclimatic record (Fig. 6; Table 3) indicates therefore that H2 and H1 events display a complex pattern on the adjacent continent. This two-phase climatic succession on land within H2 and H1 agrees with the changes detected in the marine proxy data from the same record (Fig. 6). The first phase is represented by the heaviest δ18O values of G. bulloides and the increase of N. pachyderma (s.) percentages, suggesting a strong decrease in sea surface temperatures (SST), and the absence of IRD in this region. In contrast, the second phase records the lightening of the planktic isotopic signal and the decrease in the polar foraminifera population although the presence of IRD testifies to iceberg melting off Galicia. This complex marine pattern within H2 and H1 events has already been detected further south in the SU81-18 deep-sea record (Fig. 1) (Bard et al., 2000). Comparison between our multiproxy palaeoclimatic record (Fig. 6) and the available terrestrial and marine pollen sequences in and off Iberia (Fig. 1) indicates that the impact of H2 and H1 events in Iberia is spatially variable. The Pinus reduction associated with H2, dated in the Galician margin record between 22 040 ± 180 and 21 340 ± 160 years BP, has been already detected by terrestrial and marine pollen sequences in and off northern Iberia (Fig. 1) (Pérez-Obiol and Julià, 1994; Roucoux et al., 2005). In north-eastern Spain, the decrease in Pinus percentages before 19 900 years BP detected in the Banyoles sequence and explained as the result of local factors (Pérez-Obiol and Julià, 1994) can now be interpreted as the consequence of the climatic change associated to H2. The slight expansion of Calluna recorded in the Galician margin sequence during the first phase of H2 has not been detected, however, at low altitude in north-eastern Spain where Poaceae was the dominant taxa. This suggests that heathers grow preferentially in the north-western Iberia favoured probably by Atlantic wet conditions. Southern Iberian margin cores (Fig. 1) reveal the expansion of semi-desert associations (Artemisia, Chenopodiaceae, Ephedra), suggesting an increase of dryness during the entire H2, 22 000–20 000 years BP, although no decrease of Pinus forest was detected (SU81-18, Turon et al., 2003; ODP 976, Combourieu-Nebout et al., 2002 and SO75-6KL, Boessenkool et al., 2001). In contrast, the Padul record (Pons and Reille, 1988; Fig. 1; Table 4) shows between 23 600 and 19 800 years BP an alternation

between periods of high Pinus pollen values and periods of high percentages of semi-desert plants. This suggests dryness variability in Sierra Nevada at that time or changes in pollen-input related with local factors. The two-phase climatic succession of H1 event characterised in our Galician margin record (MD31-2-4 and MD31-2-5 pollen zones, Fig. 6, Table 3) by a first cold and humid episode followed by a dry and cool phase is contemporaneous, as H2, with a unique aridity interval and no Pinus forest reduction in south-western Iberia (Fig. 1) (Boessenkool et al., 2001; Turon et al., 2003). Seemingly, high altitude sites of northern Iberia and eastern Iberian sites (Padul and Banyoles) detect one event of dryness between 15 000 and 13 000 (Table 4, Figs. 1 and 7; Laguna de la Roya, Allen et al., 1996; Quintanar de la Sierra, Peñalba et al., 1997; Laguna Masegosa, Von Engelbrechten, 1998; Lagoa Lucenza, Muñoz Sobrino et al., 2001; Laguna Lleguna and Laguna de las Sanguijuelas; Muñoz Sobrino et al., 2004). The westernmost sequences record the expansion of Calluna and Isoetes, as we observed in the first part of H1 of our record, showing that these sites are also affected by wet Atlantic influence (Lagoa Lucenza, Muñoz Sobrino et al., 2001; Laguna Lleguna and Laguna de las Sanguijuelas, Muñoz Sobrino et al., 2004; Mougás, Gomez-Orellana et al., 1998). Pinus forest cover around all high altitude sites remains weak over this time-interval while our Galician margin record (Figs. 6 and 7; Tables 3 and 4) representing also the vegetation of low and mid altitudes sees a Pinus expansion in the second part of H1. This suggests that the temperature increase was not enough to trigger Pinus expansion in high altitude areas (Fig. 1). These vegetational changes related with cold conditions in Iberia coincide with the Oldest Dryas originally identified in Danish deposits one century ago and dated older than 13 000 years BP (Mangerud et al., 1974) and not with the Older Dryas as erroneously correlated by Turon et al. (2003). Therefore, our work demonstrates that the Oldest Dryas is the terrestrial counterpart of the H1 event. 4.3.1.2. The LGM. In our record, the Last Glacial Maximum (LGM), bracketed by H2 and H1 events as established by the EPILOG program (Environmental processes of Ice age: Land, Oceans, Glaciers) (Mix et al., 2001), is characterised by the expansion of Pinus in an herbaceous-dominant environment along with scattered pockets of deciduous trees (MD31-2-3 pollen zone) (Fig. 6, Table 3). Planktic δ18O values are slightly lower than during H2 and H1 events and N. pachyderma s. decrease to very low percentages. Pinus percentages stay constant

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over this interval and there is an almost continuous slight presence of deciduous tree pollen (deciduous Quercus, Betula, Corylus and Alnus) over this period. Nevertheless herbaceous communities remain the dominant group. The presence of deciduous trees has also been detected in and off southern Iberia between 20 000 and 15 000 years BP (Table 4; Pons and Reille, 1988; Boessenkool et al., 2001; Combourieu-Nebout et al., 2002) associated with the LGM (Turon et al., 2003). Our record clearly shows that not only southern but also north-western Iberia acted as a refugium zone for certain temperate trees (deciduous Quercus, Corylus, Alnus and Betula) during the last glacial maximum corroborating what has been suggested by previous studies (Roucoux et al., 2005). However, it must be noted that deciduous trees presence is weak and that they attain their maximum expression in southern Iberia. Another interesting feature within the LGM concerns the sustaining of Ericaceae communities in north-western Iberia indicated by our Galician margin core and their slight expansion in southern Iberia detected by marine cores SU81-18 (Turon et al., 2003) and ODP 976 (Combourieu-Nebout et al., 2002). This is contemporaneous with the slight decrease of semi-desert associations in the middle altitudes of Sierra Nevada (Padul), indicating an increase of humidity in Iberia at that time.

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Laguna de las Sanguijuelas (Muñoz Sobrino et al., 2004) record a deciduous Quercus expansion between 13 000 and 11 000 years BP above 1000 m a.s.l. Our pollen analysis records higher pollen percentages of deciduous Quercus than the high altitude sequences suggesting that deciduous Quercus woodlands expanded preferentially in the lowlands and mid-altitudes of northern Iberia. Brewer et al. (2002), based on a small number of high altitude northern and low altitude southern sequences, suggested that only southern Iberia acted as a refugium zone for deciduous oak during the last glacial period. However, as previously shown by our Galician record, the mid and low-altitudes of northwestern Iberia were a refugium zone for deciduous Quercus species allowing the fast spread of these taxa during B-A climate improvement. In southern Iberia, a rapid expansion of deciduous and evergreen Quercus and other Mediterranean elements is recorded in the Late glacial interstadial of the Padul peat-bog sequence and marine records SU8118 (Turon et al., 2003), 8057 B (Hooghiemstra et al., 1992), SO75-6KL (Boessenkool et al., 2001) and ODP 976 (Combourieu Nebout et al., 1999, 2002). Indeed, a distinct phase of pioneer trees is not reflected at the beginning of this interstadial neither in southern Iberia nor in low and mid altitudinal sites of the north-western Iberia as shown by our Galician margin pollen record.

4.3.2. Marine isotopic stage 1 4.3.2.1. The Bölling-Allerød. Following the H1 event, a drastic change in the pollen assemblage and planktic stable oxygen isotopic values identifies the BöllingAllerød (B-A) temperate period (Greenland Interstadial 1—GIS 1, Late glacial interstadial). Our Galician margin pollen record (Fig. 6, Table 3) (MD97-1-1 pollen zone) detects a fast deciduous Quercus expansion and the slight development of pioneer species (Betula, Cupressaceae and Hippophae), a decrease of herbaceous associations and Pinus percentages reach maximum values. In the ocean, surface waters show an important lowering of the δ18O values suggesting, in absence of freshwater input, an oceanic warming at these North Atlantic mid-latitudes. In the northern Iberian Peninsula, the Late glacial interstadial (B-A) is characterised by the succession of pioneer associations (Juniperus–Betula–Pinus) and the more or less important expansion of deciduous trees (Fig.1 and 7; Table 4; Allen et al., 1996; Peñalba et al., 1997; Von Engelbrechten, 1998). High altitude sites of northern Iberia such as Laguna Masegosa (Von Engelbrechten, 1998), Laguna de la Roya (Allen et al., 1996), Hojos de Iregua (Gil García et al., 2002) and

4.3.2.2. The Younger Dryas cold event. Following the B-A warm phase, our Galician margin pollen record (MD97-1-2 pollen zone) sees the increase of pioneer species (Betula), grasses and semi-desert associations (Artemisia and Ephedra) at the expense of the temperate forest. These vegetational features characterise the Younger Dryas cold event (Fig. 6, Table 3). This cold episode has been detected in and off Iberia (Pons and Reille, 1988; Pérez-Obiol and Julià, 1994; Allen et al., 1996; Peñalba et al., 1997; Von Engelbrechten, 1998; Gil García et al., 2002; Turon et al., 2003) (Fig. 1, Table 4) and is associated with a slight increase of the planktic δ18O values (Hall and McCave, 2000; Schönfeld and Zahn, 2000; Löwemark et al., 2004; Turon et al., 2003). The slight decrease of deciduous Quercus, the increase of pioneer species (Betula) and the expansion of semi-desert and herbaceous plants are also represented in north-eastern Iberia as well as in continental and offshore southern Iberian sequences (Pons and Reille, 1988; Pérez-Obiol and Julià, 1994; Boessenkool et al., 2001; Turon et al., 2003). Vegetation changes related to this short event appear more drastic at high altitudinal sites of northern Iberia than at low and mid

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altitude sites of north-western Iberia (this study) and those from the south as indicated by the slight decrease of temperate trees in terrestrial and marine pollen sequences in and off southern Iberia (Fig. 7). 4.3.2.3. The Holocene. After the YD, the tree succession of deciduous Quercus, Corylus and Alnus defines the Holocene in our Galician margin record (Fig. 6, Table 3). Remarkably, during the onset of the Holocene (MD97-1-3 pollen zone), the increase of deciduous Quercus pollen percentages tightly parallels the lightening of δ18 O values (Fig. 6). However, deciduous forest attains its maximum expression slightly before sea surface water experiences its lightest δ18O values. Pinus pollen values decline steadily in the pollen zones MD97-1-3 through MD97-1-5. The end of the maximum expansion of deciduous Quercus trees and the beginning of the Corylus increase (MD97-1-4) occur contemporaneously with the beginning of the lightest δ18O isotopic values in the ocean. Deciduous Quercus gradually decreases until the end of the Holocene (from MD97-1-4 to MD97-1-6). The expansion of heaths (Ericaceae and Calluna) and ferns (as indicated by psilate Trilete spores) along with the reduction of trees (deciduous Quercus, Corylus and Betula) mark the late Holocene phases (MD97-1-5 and MD97-1-6). The minimum pollen values of Pinus are recorded in zone MD97-1-5 while maxima pollen percentages of this tree, in the successive zone MD97-16, probably reflect the reforestation of the last 350 years. In Iberia, vegetation response to climate amelioration that characterises the Holocene period looks quite similar to that of the B-A event. The settlement of the Mediterranean forest occurred very fast in southern sites (Fig. 1) as illustrated by the pollen sequences of Padul (Table 4, Pons and Reille, 1988), Charco da Candieira (Van der Knaap and van Leeuwen, 1995), SU81-18 (Turon et al., 2003), ODP 976 (Combourieu-Nebout et al., 2002), 8057 B (Hooghiemstra et al., 1992), and SO756KL (Boessenkool et al., 2001). In the north, vegetation response to the Holocene climate appears slower than in the south. The expansion of pioneer trees (Juniperus, Betula and Pinus) marks the beginning of this period in the high altitude sites of northern Iberia followed by the development of deciduous Quercus, Corylus and Alnus (Table 5; Fig. 1). This succession is also clearly detected by our Galician marine record synchronously with the decrease of planktic δ18O values which are contemporaneous with the sea surface gradual warming detected by de Abreu et al. (2003) and Schönfeld et al. (2003) in the Iberian margin. However, this vegetation succession, recorded in our Galician sequence, begins earlier, during

the Younger Dryas event, in the low and mid altitude sites than in the high altitudinal sites of north-western Iberia. The Galician margin record further suggests that the maximum development of deciduous Quercus forest leads the lightest values of planktic δ18O during the Holocene. Finally, the late Holocene interval of all Iberian marine and terrestrial sequences indicates the decline of the temperate forest during the last 5000 years. 5. Conclusions The comparison of present-day terrestrial and marine pollen samples in and off western Iberia shows that the pollen signature from the Iberian margin is similar to that of the Iberian terrestrial deposits, and, in particular, to that of the estuarine samples which recruit pollen from the vegetation colonising the adjacent hydrographic basins. Therefore, western Iberian margin pollen spectra reflect an integrated image of the regional vegetation of the adjacent continent. Furthermore, our study shows that marine pollen spectra clearly discriminate both the Mediterranean and the Atlantic plant communities colonising southern and northern Iberian Peninsula, respectively. It also identifies the present-day pattern of pollen transport in northern and southern Iberian margin during downwelling and upwelling conditions. High resolution pollen and marine proxies analysis from the Galician margin composite core (MD99-2331 and MD03-2697) shows a synchronicity of the vegetation response to the North Atlantic climatic variability during H2, LGM, H1, B-A, YD events. Comparison of this palaeoclimatic record with other marine and terrestrial pollen records shows that the beginning of both H2 and H1 cold events are associated with Pinus forest reduction in northern Iberia. It also shows the presence of two vegetation phases within H1 and H2 events, associated with an initial cold and wet episode followed by a cool and, particularly, dry episode during H1. Furthermore this comparison allows us to demonstrate that the Oldest Dryas event on the continent corresponds to the H1 event in the ocean. The slight presence of deciduous Quercus, Corylus and Alnus during the Last Glacial Maximum shows that not only southern Iberia but also northern Iberia acted as a refugium zone for these trees, though at a smaller scale. Bölling-Allerød interstadial in our sequence, which mainly represents low and mid-altitude zones, show a more rapid and great expansion of deciduous Quercus than the high altitude sites of north-western Iberia, indicating that the vegetation of low and mid-altitudes responded more rapidly to the climate variability of the North Atlantic during this interstadial. Because deciduous

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forest attained it maximum expression during the B-A interstadial in low and mid-altitudes of the north-western Iberia, the climate reversal characterising the Younger Dryas event is less marked in these zones than in the high altitude ones. The response of deciduous forest to the climate improvement that characterises the onset of the Holocene at low and mid altitudes of north-western Iberia seems to lead those observed in the high altitude sites, although the same succession of trees is observed in all these northern regions. This study confirms that marine pollen sequences from western Iberian margin are a powerful tool for accurate reconstruction of vegetation response to oceanic and atmospheric climate changes within a reliable chronological framework. Furthermore, it demonstrates the importance of including vegetation reconstructions from marine pollen sequences in future efforts to refine and model vegetation and climate dynamics in the Iberian Peninsula. Acknowledgements This study is a contribution to ARTEMIS, RESOLUTION, IDEGLACE and ECLIPSE projects and has been partially supported by the FCT research project PDCTM/PP/MAR/15251/99) and by two projects integrated in a French–Portuguese bilateral collaboration (PESSOA and ICCTI-IFREMER). We would like to thank Jean-Marie Jouanneau and Anne de Vernal, for their valuable comments which greatly improved this manuscript and also William Fletcher for the English revision. We also gratefully acknowledge Pierre Anschutz, Frans Jorissen, Jean-Marie Jouanneau and Carlos Vale for the top core samples contribution, Marie-Hélène Castéra for palynological treatments and Michel Cremer and Sébastien Zaragozi for the core X-ray interpretations. Finally, we are grateful to referees L. Dupont and H. Hooghiemstra for their constructive criticisms which greatly improve this paper. This paper is Bordeaux 1 University, EPOC, UMRCNRS 5805 Contribution no. 1605. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.marmicro. 2006.07.006. References Abrantes, F., Baas, J., Haflidason, H., Rasmussen, T., Klitgaard, D., Loncaric, N., Gaspar, L., 1998. Sediment fluxes along the north-

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eastern European Margin: inferring hydrological changes between 20 and 8 kyr. Mar. Geol. 152, 7–23. Alcara Ariza, F., Asensi Marfil, A., de Bolos y Capdevilla, O., Costa Tales, M., Arco Aguilar, M., Diaz Gonzales, T.E., Diez Garretas, B., Fernandez Prieto, J.A., Fernandez Gonzales, F., Izco Sevillando, J., Loidi Arregui, J., Martinez Parras, J.M., Navarro Andres, F., Ninot I Sugranes, J.M., Peinado Lorca, M., Rivas Martinez, S., Sanchez Mata, D., Valle Guitierrez, C., Vigo I Bonada, J., Wildpret de la Torre, W., 1987. La vegetación de España. Collection Aula Abierta. Universidad de Alcala de Henares, p. 544. Allen, J.R.M., Huntley, B., Watts, W.A., 1996. The vegetation and climate of northwest Iberia over the last 14 000 yr. J. Quat. Sci. 11, 125–147. Álvarez-Salgado, X.A., Figueiras, F.G., Pérez, F.F., Groom, S., Nogueira, E., Borges, A.V., Chou, L., Castro, C.G., Moncoiffé, G., Ríos, A.F., Miller, A.E.J., Frankignoulle, M., Savidge, G., Wollast, R., 2003. The Portugal coastal counter current off NW Spain: new insights on its biogeochemical variability. Prog. Oceanogr. 56, 281–321. Ambar, I., Fiúza, A., 1994. Some features of the Portugal Current System: a poleward slope undercurrent, an upwelling related southward flow and an autumn–winter poleward coastal surface current. 2nd International Conference on Air–Sea Interaction and on Meteorology and Oceanography of the Coastal Zone. American Meteorological Society, pp. 286–287. Ambar, I., Fiúza, A.F.G., Boyd, T., Frouin, R., 1986. Observations of a warm oceanic current flowing northward along the coasts of Portugal and Spain during Nov–Dec 1983. EOS Transaction, American Geophysical Union, vol. 67, p. 1054. Araújo, M.F., Jouanneau, J.M., Dias, J.M.A., 1994. Chemical characterisation of the main fine sedimentary deposit at the northwestern Portuguese shelf. Gaia 9, 59–65. Araújo, M.F., Jouanneau, J.M., Valerio, P., Barbosa, T., Gouveia, A., Weber, O., Oliveira, A., Rodrigues, A., Dias, J.M.A., 2002. Geochemical tracers of northern Portuguese estuarine sediments on the Iberian Shelf. Prog. Oceanogr. 52, 277–297. Arhan, M., Colin de Verdière, A., Memery, L., 1994. The eastern boundary of the subtropical North Atlantic. J. Phys. Oceanogr. 24, 1295–1316. Baas, J.H., Mienert, J., Abrantes, F., Prins, M.A., 1997. Late Quaternary sedimentation on the Portuguese continental margin: climate-related processes and products. Palaeogeogr. Palaeoclimatol. Palaeoecol. 130, 1–23. Barboni, D., Harrison, S.P., Bartlein, P.J., Jalut, G., New, M., Prentice, I.C., Sanchez-Goñi, M.-F., Spessa, A., Davis, B., Stevenson, A.C., 2004. Relationships between plant traits and climate in the Mediterranean region: a pollen data analysis. J. Veg. Sci. 15, 635–646. Bard, E., Rostek, F., Turon, J.L., Gendreau, S., 2000. Hydrological impact of Heinrich events in the subtropical Northeast Atlantic. Science 289, 1321–1324. Bard, E., Rostek, F., Ménot-Combes, G., 2004. Radiocarbon calibration beyond 20,000 14C yr B.P. by means of planktonic foraminifera of the Iberian Margin. Quat. Res. 61, 204–241. Barton, E.D., 1998. Eastern boundary of the North Atlantic — northwest Africa and Iberia. In: Robinson, A.R., Brink, K. (Eds.), The Sea, vol. 11, pp. 633–657. Blanco Castro, E., Casado González, M.A., Costa Tenorio, M., Escribano Bombín, R., García Antón, M., Génova Fuster, M., Gómez Manzaneque, F., Moreno Sáis, J.C., Morla Juaristi, C., Regato Pajares, P., Sáiz Ollero, H., 1997. Los Bosques Ibéricos, Barcelona. 572 pp. Boessenkool, K.P., Brinkhuis, H., Schönfeld, J., Targarona, J., 2001. North Atlantic sea-surface temperature changes and the climate of

112

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

western Iberia during the last deglaciation: a marine palynological approach. Global Planet. Change. 30, 33–39. Bond, G.C., Lotti, R., 1995. Iceberg discharges into the North Atlantic on millennial time-scales during the last glaciation. Science 267, 1005–1010. Bond, G., Broecker, W., Johnsen, S., McManus, J., Labeyrie, L., Jouzel, J., Bonani, G., 1993. Correlations between climate records from North Atlantic sediments and Greenland ice. Nature 365, 143–147. Bottema, S., van Straaten, L.M.J.U., 1966. Malacology and palynology of two cores from the Adriatic sea floor. Mar. Geol. 4, 553–564. Braun-Blanquet, J., Pinto da Silva, A.R., Roseira, A., 1956. Résultats de deux excursions géobotaniques à travers le Portugal septentrional et moyen. II Chenaies à feuilles caduques (Quercion occidentale) et chenaies à feuilles persistentes (Quercion faginea) au Portugal. Agron. Lusit. 18, 167–234. Brewer, S., Cheddadi, R., de Beaulieu, J.-L., Reille, M., Data contributors, 2002. The spread of deciduous Quercus throughout Europe since the last glacial period. For. Ecol. Manage. 156, 27–48. Broecker, W., Hemming, S., 2001. Climate swings come into focus. Science 294, 2308–2310. Calvo, L., Tarrega, R., Luis, E., 2002. Regeneration patterns in a Calluna vulgaris heathland in the Cantabrian mountains (NW Spain): effects of burning, cutting and ploughing. Acta Oecol. 23, 81–90. Cayre, O., Lancelot, Y., Vincent, E., Hall, M., 1999. Paleoceanographic reconstructions from planktonic foraminifera off the Iberian margin: temperature, salinity and Heinrich events. Palaeoceanography 14, 384–396. Chmura, G.L., Eisma, D., 1995. A palynological study of surface and suspended sediment on a tidal flat: implications for pollen transport and deposition in coastal waters. Mar. Geol. 128, 183–200. Combourieu Nebout, N., Londeix, L., Baudin, F., Turon, J.-L., von Grafnestein, R., Zahn, R., 1999. Quaternary marine and continental paleoenvironments in the western Mediterranean (Site 976, Alboran Sea): palynological evidence. In: Zahn, R., Comas, M.C., Klaus, A. (Eds.), Proceedings of the Ocean Drilling Program, Scientific Results, pp. 457–468. Combourieu-Nebout, N., Turon, J.-L., Zahn, R., Capotondi, L., Londeix, L., Pahnke, K., 2002. Enhanced aridity and atmospheric high-pressure stability over the western Mediterranean during the North Atlantic cold events of the past 50 ky. Geology 30, 863–866. Cross, A.T., Thompson, G.G., Zaitzeff, J.B., 1966. Source and distribution of palynomorphs in bottom sediments, southern part of Gulf of California. Mar. Geol. 4, 467–524. de Abreu, L., Shackleton, N.J., Schönfeld, J., Hall, M., Chapman, M., 2003. Millennial-scale oceanic climate variability off the Western Iberian margin during the last two glacial periods. Mar. Geol. 196, 1–20. de Vernal, A., Henry, M., Bilodeau, G., 1996. Techniques de préparation et d'analyse en micropaléontologie. Les cahiers du GEOTOP, Département des Sciences de la terre, vol. 3. Québec University, Montréal, pp. 16–27. Desprat, S., 2005. Réponses climatiques marines et continentales du Sud-Ouest de l'Europe lors des derniers interglaciaires et des entrées en glaciations. PhD Thesis, Bordeaux University, France, 282 pp. Desprat, S., Sanchez Goñi, M.F., Loutre, M.F., 2003. Revealing climatic variability of the last three millennia in northwestern Iberia using pollen influx data. Earth Planet. Sci. Lett. 213, 63–78. Desprat, S., Sánchez Goñi, M.F., Turon, J.-L., McManus, J.F., Loutre, M.F., Duprat, J., Malaizé, B., Peyron, O., Peypouquet, J.-P., 2005. Is vegetation responsible for glacial inception during periods of muted insolation changes? Quat. Sci. Rev. 24, 1361–1374.

Desprat, S., Sánchez Goñi, M.F., Turon, J.-L., Duprat, J., Malaizé, B., Peypouquet, J.-P., 2006. Climatic variability of Marine Isotope Stage 7: direct land–sea–ice correlation from a multiproxy analysis of a northwestern Iberian margin deep-sea core. Quat. Sci. Rev. 25, 1010–1026. Desprat S., Sánchez Goñi M.F., Turon J.-L., Duprat J., Malaizé B., Peypouquet J.-P., in press. Climate variability of the last five isotopic interglacials from direct land–sea–ice correlation, In: Sirocko, F., Litt, T., Claussen, M., Sánchez Goñi, M.F. (eds.), Climate of Past Interglacials. Dias, J.M.A., 1987. Dinâmica sedimentar e evolução recente de plataforma continental Portuguesa setentrional. PhD Thesis, Lisbon University, Portugal, 384 pp. Dias, J.M.A., Gonzalez, R., Garcia, C., Diaz-del-Rio, V., 2002. Sediment distribution pattern on the Galicia-Minho continental shelf. Prog. Oceanogr. 52, 215–231. Drago, T., Oliveira, A., Magalhães, F., Cascalho, J., Jouanneau, J.-M., Vitorino, J., 1998. Some evidences of northward fine sediment transport in the Portuguese continental shelf. Oceanol. Acta 21, 223–231. Drago, T., Araújo, F., Valério, P., Weber, O., Jouanneau, J.M., 1999. Geomorphological control of fine sedimentation on the northern Portuguese shelf. Bol. Inst. Esp. Oceanogr. 15, 111–122. Duplessy, J.C., Bard, E., Labeyrie, L., Duprat, J., Moyes, J., 1993. Oxygen isotope records and salinity changes in the Northeastern Atlantic Ocean during the last 18,000 years. Paleoceanography 8, 341–350. Dupont, L., Jahns, S., Marret, F., Ning, S., 2000. Vegetation change in equatorial West Africa: time-slices for the last 150 ka. Palaeogeogr. Palaeoclimatol. Palaeoecol. 155, 95–122. Elliot, M., Labeyrie, L., Bond, G., Cortijo, E., Turon, J.-L., Tisnerat, N., Duplessy, J.-C., 1998. Millennial-scale iceberg discharges in the Irminger Basin during the last glacial period: relationship with the Heinrich events and environmental settings. Paleoceanography 13, 433–446. Fiúza, A.F.G., 1984. Hidrologia e Dinâmica das Águas Costeiras Portuguesas. PhD Thesis, Lisbon University, Portugal, 294 pp. Fiúza, A.F.G., Macedo, M.E., Guerreiro, M.R., 1982. Climatological space and time variation of the Portuguese coastal upwelling. Oceanol. Acta 5, 31–40. Frouin, R., Fiúza, A.F.G., Ambar, I., Boyd, T.J., 1990. Observations of a poleward surface current off the coasts of Portugal and Spain during winter. J. Geophys. Res. 95, 679–691. Gil García, M.J., Dorado Valiño, M., Valdeolmillos Rodríguez, A., Ruiz Zapata, M.B., 2002. Late-glacial and Holocene palaeoclimatic record from Sierra de Cebollera (northern Iberian Range Spain). Quat. Intern. 93–94, 13–18. Gomez-Orellana, L., Ramil-Rego, P., Munoz Sobrino, C., 1998. Una nueva secuencia polinica y cronologica par el deposito pleistoceno de Mougas (NW de la Peninsula Iberia). Rev. Paléobiol. 17, 35–47. Gouzy, A., Malaizé, B., Pujol, C., Charlier, K., 2004. Climatic “pause” during Termination II identified in shallow and intermediate waters off the Iberian margin. Quat. Sci. Rev. 23, 1523–1528. Groot, J.J., Groot, C.R., 1966. Pollen spectra from deep-sea sediments as indicators of climatic changes in southern South America. Mar. Geol. 4, 525–537. Groot, J.J., Groot, C.R., 1971. Horizontal and vertical distribution of pollen and spores in Quaternary sequences. In: Funnel, B.M., Reidel, W.R. (Eds.), The Micropaleontology of Oceans. Cambridge University Press, Cambridge, pp. 493–504.

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114 Grousset, F.E., Labeyrie, L., Sinko, J.A., Cremer, M., Bond, G., Duprat, J., Cortijo, E., Huon, S., 1993. Patterns of ice-rafted detritus in the Glacial North-Atlantic (40–50°N). Paleoceanography 8, 175–192. Hall, I.R., McCave, I.N., 2000. Paleocurrent reconstruction, sediment and thorium focussing on the Iberian margin over the last 140 ka. Earth Planet. Sci. Lett. 178, 151–164. Haynes, R.D., Barton, E.D., 1990. A poleward flow along the Atlantic coast of the Iberian Peninsula. J. Geophys. Res. 95 (C7), 11425–11442. Heinrich, H., 1988. Origin and consequences of cyclic ice rafting in the Northeast Atlantic Ocean during the past 130,000 years. Quat. Res. 29, 142–152. Hemming, S.R., 2004. Heinrich events: massive late Pleistocene detritus layers of the North Atlantic and their global climate imprint. Rev. Geophys. 42, RG1005, doi: 10.1029/2003RG000128. Heusser, L.E., Balsam, W.L., 1977. Pollen distribution in the N.E. Pacific Ocean. Quat. Res. 7, 45–62. Heusser, L.E., Shackleton, N.J., 1979. Direct marine–continental correlation: 150,000-year oxygen isotope-pollen record from the North Pacific. Science 204, 837–839. Heusser, L.E., Stock, C.E., 1984. Preparation techniques for concentrating pollen from marine sediments and other sediments with low pollen density. Palynology 8, 225–227. Hooghiemstra, H., Stalling, H., Agwu, C.O.C., Dupont, L.M., 1992. Vegetational and climatic changes at the northern fringe of the Sahara 250 000–5 000 years BP: evidence from 4 marine pollen records located between Portugal and the Canary Islands. Rev. Palaeobot. Palynol. 74, 1–53. Hooghiemstra, H., Lézine, A-M., Leroy, S., Dupont, L., Marret, F., 2006. Late Quaternary palynology in marine sediments: a synthesis of the understanding of pollen distribution patterns in the NW African setting. Quat. Intern. 148, 29–44. Hughen, K.A., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Bertrand, C., Blackwell, P.G., Buck, C.E., Burr, G., Cutler, K.B., Damon, P.E., Edwards, R.L., Fairbanks, R.G., Friedrich, M., Guilderson, T.P., Kromer, B., McCormac, F.G., Manning, S., Bronk Ramsey, C., Reimer, P.J., Reimer, R.W., Remmele, S., Southon, J.R., Stuiver, M., Talamo, S., Taylor, F.W., van der Plicht, J., Weyhenmeyer, C.E., 2004. Marine04 marine radiocarbon age calibration, 0–26 cal kyr BP. Radiocarbon 46, 1059–1086. Huthnance, J.M., Van Aken, H.M., White, M., Barton, E.D., Le Cann, B., Coelho, E.F., Fanjul, E.A., Miller, P., Vitorino, J., 2002. Ocean margin exchange-water flux estimates. J. Mar. Syst. 32, 107–137. Jouanneau, J.M., Garcia, C., Oliveira, A., Rodrigues, A., Dias, J.A., Weber, O., 1998. Dispersal and deposition of suspended sediment on the shelf off the Tagus and Sado estuaries SW Portugal. Prog. Oceanogr. 42, 233–257. Jouanneau, J.M., Weber, O., Drago, T., Rodrigues, A., Oliveira, A., Dias, J.M.A., Garcia, C., Schimdt, S., Reyss, J.L., 2002. Recent sedimentation and sedimentary budget on the western Iberian shelf. Prog. Oceanogr. 52, 261–275. Koreneva, E.V., 1966. Marine palynological researches in the U.S.S.R. Mar. Geol. 4, 565–574. Lebreiro, S.M., Moreno, J.C., McCave, I.N., Weaver, P.P.E., 1996. Evidence for Heinrich layers off Portugal. Mar. Geol. 131, 47–56. Lopez-Jamar, E., Cal, R.M., Gonzalez, G., Hanson, R.B., Rey, J., Santiago, G., Tenore, K.R., 1992. Upwelling and outwelling effects on the benthic regime of the continental shelf off Galicia NW Spain. J. Mar. Res. 50, 465–488. Loureiro, J.J., Machado, M.L., Macedo, M.E., Nunes, M.N., Botelho, O.F., Sousa, M.L., Almeida, M.C., Martins, J.C.,

113

1986. Direcção Geral dos Serviços Hidraulicos. Monografias hidrológicas dos principais cursos de água de Portugal continental, Lisboa, p. 569. Löwemark, L., Schönfeld, J., Werner, F., Schäfer, P., 2004. Trace fossils as a paleoceanographic tool: evidence from Late Quaternary sediments of the southwestern Iberian margin. Mar. Geol. 204, 27–41. Mangerud, J., Andersen, S.T., Berglund, B.E., Donner, J.J., 1974. Quaternary stratigraphy of Norden, a proposal for terminology and classification. Boreas 3, 109–127. Mazé, J.P., Arhan, M., Mercier, H., 1997. Volume budget of the eastern boundary layer off the Iberian Peninsula. Deep-Sea Res. 44, 1543–1574. McAndrew, J.H., King, J.E., 1976. Pollen of the North American Quaternary: the top twenty. Geosci. Man 15, 41–49. McCave, I.N., Hall, I.R., 2002. Turbidity of waters over the Northwest Iberian continental margin. Prog. Oceanogr. 52, 299–313. Migeon, S., Weber, O., Faugeres, J.C., Saint-Paul, J., 1999. SCOPIX: a new imaging system for core analysis. Geo Mar. Lett. 18, 251–255. Mix, A., Bard, E., Schneider, R., 2001. Environmental processes of the ice age: land, oceans, glaciers (EPILOG). Quat. Sci. Rev. 20, 627–657. Moore, P.D., Webb, J.A., Collinson, M.E., 1991. Pollen Analysis. Blackwell, Oxford. 216 pp. Mudie, P.J., 1982. Pollen distribution in recent marine sediments, eastern Canada. Can. J. Earth Sci. 19, 729–747. Muller, J., 1959. Palynology of recent Orinoco delta and shelf sediments. Micropaleontology 5, 1–32. Muñoz Sobrino, C., Ramil-Rego, P., Rodriguez Guitián, M.A., 1997. Upland vegetation in the north-west peninsula after the last glaciation: forest history and deforestation dynamics. Veg. Hist. Archaeobot. 6, 215–233. Muñoz Sobrino, C., Ramil-Rego, P., Rodriguez Guitián, M.A., 2001. Vegetation in the mountains of northwest Iberia during the last glacial–interglacial transition. Veg. Hist. Archaeobot. 10, 7–21. Muñoz Sobrino, C., Ramil-Rego, P., Gomez-Orellana, L., 2004. Vegetation of the Lago Sanabria area (NW Iberia) since the end of the Pleistocene: a palaeoecological reconstruction on the basis of two new pollen sequences. Veg. Hist. Archaeobot. 13, 1–22. Oliveira, A., Rodrigues, A., Jouanneau, J.M., Weber, O., Dias, J.A., Vitorino, J., 1999. The suspended matter distribution and composition in the northern Portuguese margin. Bol. Inst. Esp. Oceanogr. 15, 101–109. Oliveira, A., Rocha, F., Rodrigues, A., Jouanneau, J.M., Dias, J.M.A., Weber, O., Gomes, C., 2002. Clay mineral from the sedimentary cover from the Northwestern Iberian shelf. Prog. Oceanogr. 52, 233–247. Peck, R.M., 1973. Pollen budget studies in a small Yorkshire catchment. In: Birks, H.J.B., West, R.G. (Eds.), Quaternary Plant Ecology. The 14th Symposium of the British Ecological Society, University of Cambridge, Blackwell Scientific Publications, pp. 43–60. Peñalba, C., 1994. The history of the Holocene vegetation in northern Spain from pollen analysis. J. Ecol. 82, 815–832. Peñalba, M.C., Arnold, M., Guiot, J., Duplessy, J.-C., de Beaulieu, J.-L., 1997. Termination of the Last Glaciation in the Iberian Peninsula inferred from the pollen sequence of Quintanar de la Sierra. Quat. Res. 48, 205–214. Pérez-Obiol, R., Julià, R., 1994. Climatic change on the Iberian Peninsula recorded in a 30000 yr pollen record from Lake Banyoles. Quat. Res. 41, 91–98. Peyron, O., Guiot, J., Cheddadi, R., Tarasov, P., Reille, M., de Beaulieu, J.-L., Bottema, S., Andrieu, V., 1998. Climatic reconstruction in Europe for 18,000 yr BP from pollen data. Quat. Res. 49, 183–196.

114

F. Naughton et al. / Marine Micropaleontology 62 (2007) 91–114

Pingree, R.D., Le Cann, B., 1990. Structure, strength and seasonality of the slope currents in the Bay of Biscay region. J. Mar. Biol. Assoc. U.K. 70, 857–885. Pingree, R.D., Le Cann, B., 1992. Three anti-cyclonic slope water oceanic eddies (SWODDIES) in the southern Bay of Biscay. Deep-Sea Res. 39, 1147–1175. Polunin, O., Walters, M., 1985. A Guide to the Vegetation of Britain and Europe. Oxford University Press, New York. 238 pp. Pons, A., Reille, M., 1986. Nouvelles recherches pollenanalytiques à Padul (Granada): La fin du dernier glaciaire et l'Holocène. In: López-Vera, E. (Ed.), Quaternary Climate in Western Mediterranean, University Autónoma de Madrid, pp. 405–420. Pons, A., Reille, M., 1988. The Holocene- and Upper Pleistocene pollen record from Padul (Granada Spain): a new study. Palaeogeogr. Palaeoclimatol. Palaeoecol. 66, 243–263. Reille, M., 1992. Pollen et spores d'Europe et d'Afrique du Nord. Laboratoire de botanique historique et palynologie, Marseille, p. 520. Rios, A.F., Pérez, F.F., Fraga, F., 1992. Water masses in the upper and middle North Atlantic east of the Açores. Deep-sea Res. 39, 645–658. Roucoux, K.H., Shackleton, N.J., de Abreu, L., Schönfeld, J., Tzedakis, P.C., 2001. Combined marine proxy and pollen analyses reveal rapid Iberian vegetation response to North Atlantic millennial-scale climate oscillations. Quat. Res. 56, 128–132. Roucoux, K.H., de Abreu, L., Shackleton, N.J., Tzedakis, P.C., 2005. The response of NW Iberian vegetation to North Atlantic climate oscillations during the last 65 kyr. Quat. Sci. Rev. 24, 1637–1653. Ruiz Zapata, M.B., Gil Garcia, M.J., Dorado Valiño, M., Valdeolmillos Rodrigues, A., Vegas, J., Pérez-Gonzalez, A., 2002. Clima y vegetación durante el tardiglaciar y el Holoceno en la Sierra de Neilla (Sistema Ibérico Noroccidental). Cuatern. Geomorfol. 16, 9–20. Sánchez Goñi, M.F., Hannon, G., 1999. High altitude vegetational patterns on the Iberian Mountain chain (north-central Spain) during the Holocene. Holocene 9, 39–57. Sánchez Goñi, M.F., Eynaud, F., Turon, J.-L., Shackleton, N.J., 1999. High resolution palynological record off the Iberian margin: direct land–sea correlation for the Last Interglacial complex. Earth Planet. Sci. Lett. 171, 123–137. Sánchez Goñi, M.F., Turon, J.-L., Eynaud, F., Gendreau, S., 2000. European climatic response to millennial-scale climatic changes in the atmosphere–ocean system during the Last Glacial period. Quat. Res. 54, 394–403. Sánchez Goñi, M.F., Cacho, I., Turon, J.-L., Guiot, J., Sierro, F.J., Peypouquet, J.-P., Grimalt, J.O., Shackleton, N.J., 2002. Synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the Mediterranean region. Clim. Dyn. 19, 95–105. Sánchez Goñi, M.F., Loutre, M.F., Crucifix, M., Peyron, O., Santos, L., Duprat, J., Malaizé, B., Turon, J.-L., Peypouquet, J.-P., 2005. Increasing vegetation and climate gradient in Western Europe over the Last Glacial Inception (122–110 ka): data-model comparison. Earth Planet. Sci. Lett. 231, 111–130. Santos, L., Vidal Romani, J.R., Jalut, G., 2000. History of vegetation during the Holocene in the Courel and Queixa Sierras, Galicia, northwest Iberian Peninsula. J. Quat. Sci. 15, 621–632. Schönfeld, J., Zahn, R., 2000. Late glacial to Holocene history of the Mediterranean outflow: evidence from benthic foraminiferal assemblages and stable isotopes at the Portuguese margin. Palaeogeogr. Palaeoclimatol. Palaeoecol. 159, 85–111.

Schönfeld, J., Zahn, R., de Abreu, L., 2003. Surface and deep water response to rapid climate changes at the Western Iberian Margin. Glob. Planet. Change 36, 237–264. Shackleton, N.J., Hall, M.A., Vincent, E., 2000. Phase relationships between millennial scale events 64,000–24,000 years ago. Paleoceanography 15, 565–569. Sprangers, M., Dammers, N., Brinkhuis, H., van Weering, T.C.E., Lotter, A.F., 2004. Modern organic-walled dinoflagellate cyst distribution offshore NW Iberia; tracing the Upwelling System. Rev. Palaeobot. Palynol. 128, 97–106. Stanley, E.A., 1966. The application of palynology to oceanology with reference to the northwestern Atlantic. Deep-Sea Res. 13, 921–939. Stuiver, M., Reimer, P.J., 1993. Extended 14C database and revised CALIB radiocarbon calibration program. Radiocarbon 35, 215–230. Stuiver, M., Reimer, P.J., Reimer, R.W., 2005. CALIB 5.0. (WWW program and documentation). Telford, R.J., Heegaard, E., Birks, H.J.B., 2004. The intercept is a poor estimate of a calibrated radiocarbon age. Holocene 14, 296–298. Thouveny, N., Moreno, E., Delanghe, D., Candon, L., Lancelot, Y., Shackleton, N.J., 2000. Rock-magnetic detection of distal ice rafted debries: clue for the identification of Heinrich layers on the Portuguese margin. Earth Planet. Sci. Lett. 180, 61–75. Turon, J.-L., 1984. Le palynoplancton dans l'environnement actuel de l'Atlantique nord-oriental. Evolution climatique et hydrologique depuis le dernier maximum glaciaire. PhD Thesis, Bordeaux I University, France, 313 pp. Turon, J.-L., Lézine, A.-M., Denèfle, M., 2003. Land–sea correlations for the last glaciation inferred from a pollen and dinocyst record from the Portuguese margin. Quat. Res. 59, 88–96. Tzedakis, P.C., Roucoux, K.H., de Abreu, L., Shackleton, N.J., 2004. The duration of forest stages in southern Europe and interglacial climate variability. Science 306, 2231–2235. Vale, C., 1990. Temporal variations of particulate metals in the Tagus river estuary. Sci. Total Environ. 97–98, 137–154. Valdès, C.M., Gil Sanchez, L., 2001. La transformación histórica del paisaje forestal en Galicia, Ministerio de Medio Ambiente. 159 pp. Van der Kaars, S., de Deckker, P., 2003. Pollen distribution in marine surface sediments offshore Western Australia. Rev. Palaeobot. Palynol. 124, 113–129. Van der Knaap, W.O., van Leeuwen, J.F.N., 1995. Holocene vegetation succession and degradation as responses to climatic change and human activity in the Serra de Estrela, Portugal. Rev. Palaeobot. Palynol. 89, 153–211. Van Weering, T.C.E., McCave, I.N., 2002. Dedication to Roland Wollast. Prog. Oceanogr. 52, 121–122. Van Weering, T.C.E., de Stigter, H.C., Boer, W., Haas, H., 2002. Recent sediment transport and accumulation on the NW Iberian margin. Prog. Oceanogr. 52, 349–371. Vanney, J.R., Mougenot, D., 1981. La plate-forme continentale du Portugal et les provinces adjacentes: analyse géomorphologique. Mem. Serv. Geol. Port., Lisbon, p. 145. Vitorino, J., Oliveira, A., Jouanneau, J.M., Drago, T., 2002. Winter dynamics on the northern Portuguese shelf: Part 1. Physical processes. Progr. Oceanogr. 52, 129–153. Von Engelbrechten, S., 1998. Late-glacial and Holocene vegetation and environmental history of the sierra de Urbión, North-Central Spain. PhD Thesis, Dublin University, Trinity College, Ireland, 212 pp.