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The detailed analysis of the International Marine Past Global Changes Study core MD99-2343 recovered from a sediment drift at 2391 m water depth north of the island of Minorca illustrates the effects of climate variability on thermohaline circulation in the western Mediterranean during the last 12 kyr. Geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the Western Mediterranean Basin during the Holocene. Superimposed on the general trend, eight centennial- to millennial-scale abrupt events appear consistently in both grain size and geochemical records, which supports the occurrence of episodes of deepwater overturning reinforcement in the Western Mediterranean Basin. The observed periodicity for these abrupt events is in agreement with the previously defined Holocene cooling events of the North Atlantic region, thus supporting a strong Atlantic-Mediterranean climatic link at high-frequency time intervals during the last 12 kyr. The rapid response of the Mediterranean thermohaline circulation to climate change in the North Atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes.

[EN]The main objective of this work is to explore the Guadalquivir basin and the Gulf of Cadiz to obtain continuous sediment records for the interval of the Messinian Salinity Crisis on the Atlantic side of the Iberian peninsula so as to analyse the possible paleoenvironmental, tectonic or paleoclimatic changes in a region which was only a few kms away from the Mediterranean coasts during this time period.

Se estudia la paleoclimatología en el Mar de Alborán utilizano la técnica de los análogos modernos. Planktonic foraminifers from core ODP site 977a have been studied to estimate sea surface temperatures (SST) inthe Alboran Sea between 245 and 145 kyr. Similar studies have been performed in this basin but only for the last150 kyr (Perez-Folgado et al., 2004). SSTs in this basin are highly controlled by the atlantic superficial incoming fluxthrough the Gibraltar Strait. In this study we estimate paleotemperatures with the modern analog techniquewhich consists on a comparison between core and modern sample assemblages. This method assumes thatsimilar planktonic foraminifer assemblages develop under the same ecological conditions and that foraminiferecological preferences have not changed in time. This technique also provides a dissimilarity index (between 0 and1) which depends on the liability of the estimation obtained. In this study we used Kallel et al. (1997) moderndatabase which contains a total of 253 samples, 123 from the North Atlantic and 130 from the MediterraneanSea. For the estimations we used PaleoAnalogs 2.0, computer program developed by the University of Salamanca(Theron et al., 2004). A small SST difference exists between substages 7.3, 7.2 and 7.1. Important millennialcyclicities (7.4, 5.6 and 4.6 kyr) occur during the whole studied period, both in warm and cold intervals, althoughchanges seem to be broader during cold ones. Seasonality is higher during the warmer substages, 7.5 and 7.3,whereas it is smaller during the strong Northern Hemisphere summer insolation minimum in substage 7.4.

Este catálogo da a conocer el material paleontológico, depositado en el Departamento de Paleontología de la Universidad de Salamanca, fruto de las investigaciones que se vienen llevando a cabo en el Neógeno marino español. En esta primera edición se relacionan los Moluscos (Gasterópodos y Bivalvos) del Plioceno de la provincia de Huelva. El material ha sido estudiado y determinado en el curso de realización de Tesis Doctorales y otros trabajos, en el área citada, y enmarcados dentro del campo de investigación que desarrolla el Departamento.

Down-core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in International Marine Past Global Changes Study (IMAGES) core MD99-2343 in order to study the interactions between climate change in the Northern Hemisphere and the western Mediterranean thermohaline circulation at times of Heinrich events (HE). Our results confirm the antiphase correlation between enhanced North Atlantic Deep Water formation and low ventilation in the Mediterranean. However, this study reveals that this antiphase relationship in deepwater formation between the North Atlantic and Mediterranean was interrupted during times of HE when the injection of large volumes of water from melting icebergs reached the entrance to the Mediterranean. These events, which lasted less than 1000 years, are represented by pronounced decreases in both planktonic delta(18)O and benthic delta(13)C signals. Lower salinities of Mediterranean surface water resulted in a slowdown of western Mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation.

Tesis por compendio de publicaciones, [ES]Para la realización de este trabajo, se han abordado diferentes casos de estudio específicos, mediante la aplicación de técnicas de análisis de diferente naturaleza, concretados en artículos científicos. Estos artículos pueden agruparse e identificarse con tres bloques generales de i) reconstrucción paleoceanográfica de alta resolución en el márgen Ibérico a partir de la señal del complejo Gephyrocapsa, ii) evaluación de la sensibilidad fotosintética de Gephyrocapsa al CO2, a partir se la sensibilidad del fraccionamiento isotópico del carbono orgánico durante la fotosíntesis (εp) y de sus efectos vitales en los isótopos de oxígeno y carbono en el sector Oeste del Atlántico tropical y iii) caracterización morfométrica y de los cambios en la calcificación del complejo Gephyrocapsa en el Atlántico Norte y el sector occidental del mar Mediterráneo., [EN]Here we present different specific studies through the application of a suite of analytical techniques, which are specified and detailed in three already published scientific articles, one in a state of under review, and one in preparation to be submitted. These studies can be grouped and identified in three general blocks: i) high-resolution paleoceanographic reconstruction in the Iberian margin using the signal of Gephyrocapsa complex, ii) evaluation of the photosynthetic sensitivity of Gephyrocapsa to CO2, from the values of carbon isotopic fractionation during photosynthesis (εp), and the Gephyrocapsa coccolith vital effects at the western tropical Atlantic, and iii) characterization of the changes in morphometry and calcification of the Gephyrocapsa complex along the North to South transect trough different regions in the North Atlantic and the western Mediterranean sea

[ES] El estudio de las asociaciones de foraminíferos (planctónicos y bentónicos) revela que, durante el último ciclo glacial, el Mediterráneo Occidental sufrió cambios climáticos y oceanográficos debidos a la variabilidad milenaria registrada durante el mismo y marcada por los eventos Heinrich y los ciclos Dansgaard-Oeschger. Considerando las asociaciones de foraminíferos planctónicos, se puede decir que para el periodo glacial, las mismas varían según la ciclicidad Dansgaard-Oeschger, de tal manera que durante los estadiales se registra microfauna que marca condiciones de baja temperatura del agua superficial y un incremento en la turbulencia de la columna de agua, mientras que durante los interestadiales la asociación está dominada por microfauna de ambiente cálido y productivo. Destacar que para los eventos Heinrich se presentan incrementos de la especie Neogloboquadrina pachyderma (dextrógira) que pueden ser atribuidos a la entrada de agua de fusión, lo que supondría una estratificación en la columna de agua con desarrollo de un Máximo de Clorofila Profundo (DCM -Deep Chlorophyll Maximum-). Ya en el interglacial se han reconocido las mismas condiciones oceanográficas que se dieron en el Mediterráneo Oriental durante la formación del sapropel 1, con estratificación en la columna de agua y desarrollo de un DCM, tras lo cual las condiciones oceanográficas se restablecen, registrándose una microfauna planctónica típica de mar cálido. Por lo que respecta a la asociación de foraminíferos bentónicos, permite dividir el periodo glacial en dos subperiodos: superior e inferior. Para el glacial inferior la asociación registra la variabilidad Dansgaard-Oeschger, de tal manera que durante los estadiales se puede observar un incremento en la epifauna, característica de ambientes con alta oxigenación, lo que indicaría unas condiciones de mejor ventilación en la cuenca debido al clima más frío y seco registrado.

[EN]From a climatic and oceanographic point of view, the North Atlantic is a very important area because the main sources of deep water formation, which drive thermohaline circulation, are in the Norwegian-Greenland Sea and the Labrador Sea. Hence, changes in North Atlantic circulation have a great impact on global circulation. In this Thesis a section of the North Atlantic sediment core IODP Site U1314 was studied. This core was recovered in a key area for studying North Atlantic current variations and IRD discharges as well as changes in the strength of the Atlantic Meridional Overturning circulation (AMOC). Several records were obtained from micropaleontological and geochemical analysis on foraminifers: stable oxygen and carbon isotopes from benthic foraminifers (mainly C. wuellerstorfi), stable oxygen and carbon isotopes from two planktic foraminifer species N. pachyderma sin y dex, IRD fluxes, planktic foraminifer assemblages and trace elements from the planktic foraminifer N. pachyderma sin. Additionally, time series analyses were performed on all the records above mentioned and on the records from the Antarctic ice core EDC. The first aim of this Thesis was establishing the chronological framework for the studied interval. We tuned our benthic δ18O with the Antarctic temperatures from EDC ice core. The studied interval encompasses from MIS 19 to 11, which means from 800 to 400 thousand years (ka) approximately. Using the paleoceanographic and paleoclimatic proxies above mentioned, we propose that glacial-interglacial cycles can be divided in five stages: 1) Early interglacial stage. During this stage the Arctic and Polar fronts were located in a position similar to their present day position. The AMOC was very active and the NAC reached the Norwegian-Greenland Sea and the Labrador Sea where it sank to generate deep waters, like it happens nowadays. 2) Late interglacial stage. During this stage the Arctic front started to migrate southeastwards reaching a position near Site U1314. However, the low benthic δ18O values indicated that the ice sheets did not started to grow. Deep water formation in the Labrador Sea was reduced lowering the input of NAC waters in the subpolar gyre and hence the salinity of the gyre. Conversely in the Norwegian-Greenland Sea deep water formation was very strong. 3) First stage of glacial periods. The beginning of glacial periods was established at the inflection of benthic δ18O record, in other word when the ice volume began to grow. During this stage the AMOC was active in the Norwegian-Greenland Sea because the Arctic and Polar fronts were rather north in this area. That favoured the fresh water transport towards high latitudes and the accumulation of snow in the continents. In the Labrador Sea a perennial sea ice cover prevented convection and deep waters were not produced at this area. The Arctic front was located between Site U1314 and ODP Site 980, whereby the NAC flowed through the East Atlantic and still reached the Norwegian-Greenland Sea. It is likely that deep waters progressively cooled and that cooling was transmitted through the AMOC to the Southern Hemisphere, and the whole ocean. 4) Second stage of glacial periods. This stage began with the first ice-rafting event and it is characterised by a progressive ice sheet growth that was interrupted by several millennial-scale events that we denominated ice sheet collapse events (ISCE). As a consequence of the first iceberg discharges the AMOC was disturbed and intermediate water (GNAIW) was generated instead of deep water (NADW). The ISCE present two phases, first iceberg discharges dampened the formation of GNAIW and because of the see-saw effect, the Southern Hemisphere warmed and CO2 was outgased from the ocean to the atmosphere. Subsequently an abrupt warming occurred in the Northern Hemisphere melting part of the ice sheets. The ISCE present a similar sequence of events as the Heinrich events and the subsequent interstadial that where described for the last glacial period. During the progressive ice sheet growth the Arctic front was at approximately E-W and was located at 55 º N. The NAC reached Site 980 and GNAIW was likely generated south of 60º N. Conversely, during the warm phase of the ISCE the Arctic front migrated northwards, the NAC reached northernmost positions and the GNAIW was generated northernmost too. 5) Late glacial periods-termination. At the end of glacial periods the Arctic front began to retreat slowly and then at the Termination the Arctic front migrated northwestwards abruptly as the ice volume was reduced. The NAC entered in the Norwegian-Greenland Sea and the Labrador Sea where it resume the deep water formation, and hence, the AMOC. Planktic foraminifer assemblages showed abrupt shifts between cold and warm assemblages. N. pachyderma dex, G. inflata y G. bulloides were dominant during the warm periods whereas during cold periods the assemblage was almost monospecific and N. pachyderma sin dominated. The abrupt shifts were related to the position of the Arctic front respect to the studied area, which determined the presence of NAC waters or Arctic waters. When the Arctic front was near Site U1314 high percentages of T. quinqueloba were recorded. Paleotemperature reconstructions performed with transfer functions for planktic foraminifers and Mg/Ca paleothermometry showed that Mg/Ca paleothermometry is reliable when the Arctic front was north of Site U1314 whereas the presence of the Arctic waters interfered in the Mg/Catemperature relationship, supporting previous works. Additionally the analysis of temperatures and δ18O records on planktic foraminifer tests of N. pachyderma sin and dex suggests that during interglacial periods the difference between both species is related to seasonality and stratification of the water column. During MIS 15 and 11 seasonality was higher, with cooler winters and warmer summers than during MIS 17 and 13 summer stratification of the water column was higher than during MIS 17 and 13. The differences in seasonality might be related with the strength of summer winds. During interglacial periods the presence of sea ice during most of the year favoured that both species lived during the same season and in the same water mass because the sea ice melting might have produced a low salinity lid that prevented water mixing. The iceberg discharges did not produce significant changes in the seawater δ18O except at the Terminations. Time series analyses performed on the different records of the Thesis and their comparison with the spectral analyses of EDC records, showed a progressive importance of the precession band in the climatic cycles. From the marine-establishment of the East Antarctic Ice Sheet the Southern Hemisphere fluctuated between in and out phase responses respect to the Northern hemisphere until MIS 12. This change produced a northward shift in the ITCZ increasing moisture transport to higher latitudes and contributing to the snow accumulation and the large ice sheet growth of MIS 16. From MIS 16 to 12 high latitude northern hemisphere insolation controlled global climate changes and the CO2 concentration, but the climate was still highly influenced by obliquity. After MIS 12 the ITCZ migrated near the equator, sea surface temperatures in the Southern Hemisphere increased and ice volume changes occurred in phase., [ES] El Atlántico norte es una zona muy sensible a los cambios climáticos y oceanográficos puesto que las principales zonas de formación de aguas profundas, que son el motor de la circulación termohalina, se encuentran en el Mar del Labrador y el Mar de Noruega-Groenlandia. Por tanto los cambios en la circulación oceánica del Atlántico norte tienen una gran influencia en la circulación global. En esta Tesis Doctoral se ha estudiado un testigo de sedimento oceánico que está ubicado en un lugar clave dentro del Atlántico subpolar. El área de estudio nos ha permitido analizar tanto cambios superficiales, en especial variaciones en la corriente Noratlántica (NAC) y eventos de descarga de icebergs, como cambios en la intensidad de la circulación profunda. En esta Tesis Doctoral se ha elaborado un registro de isótopos estables de oxígeno y carbono en foraminíferos bentónicos (principalmente C. wuellerstorfi), un registro de isótopos estables de oxígeno y carbono en dos especies de foraminíferos planctónicos, N. pachyderma sin y dex, un registro de acumulación de IRD, un registro de cambios en las asociaciones de foraminíferos planctónicos y un registro de la proporción de elementos traza en las conchas de N. pachyderma sin. Además se ha realizado un análisis espectral de los registros anteriormente mencionados y de otros como los del testigo de hielo antártico EDC. Uno de los objetivos prioritarios de esta Tesis ha sido establecer el modelo de edad para el intervalo estudiado. Para ello se ha correlacionado el registro de δ18O de foraminíferos bentónicos con el registro de temperatura obtenido a partir del testigo de hielo antártico EDC. El intervalo de estudio comprende desde el MIS 19 al 11, que corresponde a un intervalo desde hace 800 a 400 mil años (ka) aproximadamente. En base a las herramientas paleoceanográficas y paleoclimáticas utilizadas en este trabajo hemos identificado una serie de patrones que nos ha permitido establecer una división de los ciclos climáticos en cinco fases: 1) Fase inicial de los periodos interglaciales. Durante esta fase los frentes Ártico y Polar estaban situados en una posición similar a la que presentan hoy en día. La circulación termohalina era muy activa y la NAC llegaba al Mar de Noruega-Groenlandia y al Mar del Labrador donde se hundía para formar aguas profundas, como ocurre en el presente. 2) Fase tardía de los periodos interglaciales. En esta fase el frente Ártico empezó a migrar hacia el sureste cerca del Site U1314. Sin embargo, los valores de δ18O de foraminíferos bentónicos indican que los casquetes de hielo aún no habían empezado a crecer. La formación de aguas profundas en el Mar del Labrador se redujo y las aguas del giro subpolar disminuyeron su salinidad por la reducción de la llegada de aguas de la NAC. En cambio, en el Mar de Noruega-Groenlandia la formación de aguas profundas era muy activa. 3) Primera fase de los periodos glaciales. El inicio de los periodos glaciales se ha establecido como el punto de inflexión de los valores de δ18O de foraminíferos bentónicos, es decir cuando comenzó a aumentar el volumen de hielo. Durante esta fase la circulación termohalina continuó activa en el Mar de Noruega-Groenlandia porque los frentes Ártico y Polar aún no habían migrado hacia el sur en esa zona. Este hecho favoreció el transporte de vapor de agua hacia altas latitudes y por ende la acumulación de hielo en los continentes. Sin embargo, una banquisa de hielo perenne cubría gran parte del Mar del Labrador, por lo que la convección dejó de producirse en esta área. El frente Ártico se situaba entre el Site U1314 y el Site 980 de ODP, de modo que la NAC fluía por el este del Atlántico pero aún llegaba al Mar de Noruega-Groenlandia. Las aguas profundas probablemente fueron enfriándose durante esta fase y ese enfriamiento se transmitió al hemisferio sur, y a todo el océano, a través de la circulación termohalina. 4) Segunda fase de los periodos glaciales. Esta fase comienza con la primera descarga de IRD, y se caracteriza por un crecimiento progresivo de los mantos de hielo que fue interrumpido por varios eventos de escala milenaria, que hemos denominado ice sheet collapse events (ISCE). La primera descarga de icebergs da comienzo a la ralentización de la circulación termohalina y a la generación de aguas intermedias (GNAIW) en vez de profundas (NADW). Los ISCE comienzan con una descarga de IRD hacia el Atlántico norte que ralentiza la formación de GNAIW y produce un calentamiento en el hemisferio sur por el efecto see-saw, que a su vez da lugar a la liberación de CO2 del océano a la atmósfera. A esta primera etapa de enfriamiento extremo en el hemisferio norte le sucede un calentamiento brusco del agua superficial que incrementa la ablación de las grandes masas de hielo en el hemisferio norte. La estructura de los ISCE es similar a la de un evento Heinrich y su posterior interestadial, descritos para el último periodo glacial. Durante las etapas de acumulación de hielo el frente Ártico estaba a unos 55º N con una dirección casi E-W, las aguas de la NAC solamente llegaban al Site 980 y la GNAIW se generaba probablemente al sur de los 60º N. En cambio, durante los periodos cálidos de los ISCE el frente Ártico migró hacia el norte, la NAC llegaba más al norte y la GNAIW se formaba también más al norte. 5) Fase final de los periodos glaciales y Terminación. Durante esta fase el frente Ártico comenzó a retroceder lentamente hasta que durante la Terminación se produce una brusca migración hacia el noroeste mientras se reduce el volumen de hielo. La NAC va penetrando hacia el norte y reactiva la formación de aguas profundas tanto en el Mar de Noruega-Groenlandia como en el Mar del Labrador. Las asociaciones de foraminíferos planctónicos nos muestran cambios muy bruscos entre la asociación predominante en los periodos cálidos, donde dominan las especies transicionalessubpolares N. pachyderma dex, G. inflata y G. bulloides, y la asociación prácticamente monoespecífica de N. pachyderma sin que predomina durante los periodos fríos. Estos cambios bruscos se deben a la posición del frente Ártico, que determina la presencia de aguas de la corriente estudio se registran altos porcentajes de T. quinqueloba. Los cálculos de paleotemperaturas a partir de la relación Mg/Ca y de las asociaciones de foraminíferos planctónicos nos muestran que las temperaturas de Mg/Ca en latitudes altas son fiables durante los periodos interglaciales, cuando el frente Ártico estaba al norte del Site U1314, mientras que la presencia de las aguas árticas interfiere en la relación del Mg/Ca con la temperatura, corroborando estudios previos. El análisis de las temperaturas junto a los análisis del δ18O en las conchas de los foraminíferos planctónicos N. pachyderma sin y dex nos muestra que durante los periodos interglaciales la diferencia entre ambas especies indica estacionalidad y mezcla en la columna de agua. Los MIS 15 y 11 presentaron una mayor estacionalidad con veranos más cálidos e inviernos más fríos que los MIS 17 y 13, en parte como consecuencia de una mayor estratificación de la columna de agua durante el verano. Estas diferencias en la estratificación pudieron estar relacionadas con un aumento en la fuerza de los vientos durante los veranos de los MIS 17 y 13. Durante los periodos glaciales la presencia de banquisa de hielo durante la mayor parte del año favoreció que ambas especies vivieran en la misma estación y en la misma masa de agua dentro de la columna dado que es posible que el deshielo de la banquisa produjera una gran estratificación. Las descargas de icebergs no produjeron cambios significativos en el δ18O del agua excepto en las Terminaciones. El análisis de la ciclicidad de los diferentes registros elaborados en esta Tesis y su comparación con los registros de EDC, nos ha permitido observar un progresivo aumento en la importancia de la precesión en los ciclos climáticos. Desde el establecimiento casquete de hielo del este de la Antártida sobre la plataforma marina el hemisferio Sur ha alternado entre estar en fase o desfasado respecto al hemisferio norte hasta que en el MIS 12 se establece en fase. Este periodo de adaptación provocó un desplazamiento en la ITCZ hacia el norte que aumentó el transporte de vapor de agua al hemisferio norte contribuyendo a la formación de grandes masas de hielo que alcanzaron su máximo desarrollo en el MIS 16. Desde el MIS 16 al 12 la insolación sobre altas latitudes del hemisferio norte controlaba los cambios climáticos globales y la concentración de CO2, pero el clima estaba aún estaba influido por la oblicuidad. A partir del MIS 12 la ITCZ se situó más cerca del ecuador, las temperaturas durante los interglaciales aumentaron en el hemisferio sur y los cambios de volumen de hielo se produjeron en fase en ambos hemisferios.

[ES]La presente tesis doctoral tiene como objetivo estudiar la variabilidad temporal de la productividad de cocolitóforos y la evolución climática en el mar Mediterráneo occidental durante los últimos 25 ka mediante el estudio micropaleontológico y geoquímico de registros sedimentarios marinos. Los cocolitóforos son un grupo de algas unicelulares marinas y conforman uno de los principales componentes del fitoplancton en los océanos actuales. Estos organismos secretan placas calcificadas (cocolitos) que, tras su sedimentación en los fondos marinos, pueden preservarse en el registro fósil. La abundancia y diversidad de los cocolitóforos están altamente influenciadas por las condiciones ambientales en las que proliferan, por lo que el estudio de los cocolitos preservados en el registro sedimentario aporta información útil para la realización de reconstrucciones paleoambientales. En esta tesis doctoral se han analizado las asociaciones cocolitoforales de dos testigos sedimentarios pertenecientes al mar de Alborán: el testigo CEUTA10PC08 que abarca desde 25 hasta 4,5 ka, y el testigo HER-GC-T1 que abarca desde 23,5 hasta 0 ka. También se han analizado los registros de isótopos de oxígeno y temperatura superficial marina (TSM) de ambos testigos y algunos registros de marcadores orgánicos del testigo HER-GC-T1. El estudio combinado de todos los registros mencionados a alta resolución ha permitido reconstruir la variabilidad oceanográfica y climática del mar Mediterráneo occidental desde el Último Máximo Glacial (23 ka). También se han considerado las asociaciones cocolitoforales en un conjunto de muestras de sedimento superficial con el objetivo de explorar el potencial de los cocolitóforos para la reconstrucción cuantitativa de variables ambientales mediante el desarrollo de funciones de transferencia. La productividad de cocolitóforos en el mar de Alborán está altamente influenciada por procesos climáticos tanto globales como locales desde el Último Máximo Glacial. En términos generales, se ha observado que la productividad ha sido mayor en el área más próxima al estrecho de Gibraltar, debido a la influencia del agua atlántica. Esta masa de agua resulta ser un mecanismo transmisor de la señal climática del Atlántico norte a la región Mediterránea. Sin embargo, a medida que el agua atlántica se mezcla con la mediterránea, los procesos locales y la configuración hidrográfica ejercen una mayor influencia sobre la productividad de los cocolitóforos. El estudio de los cambios observados en los registros de cocolitóforos, isótopos de oxígeno, TSM, etc., ha permitido contextualizar la variabilidad temporal de la productividad de cocolitóforos y las dinámicas de la columna de agua dentro de cambios climáticos globales conocidos como los estadiales asociados a los eventos Heinrich, el Bølling-Allerød o el Younger Dryas. Durante el Holoceno se ha observado que la productividad de los cocolitóforos en el testigo HER-GC-T1 está estrechamente ligada a otros procesos de origen físico, como la producción de Agua Mediterránea Profunda Occidental en el golfo de León y el control hidráulico que ejerce el estrecho de Gibraltar. Los patrones de circulación atmosférica son propuestos como responsables últimos de la variabilidad de la productividad de los cocolitóforos durante el Holoceno. A este respecto, se ha observado una relación entre los procesos físicos arriba mencionados y la Oscilación del Atlántico Norte, resultado que pone de manifiesto la teleconexión climática existente entre el Atlántico norte y el mar Mediterráneo occidental. Por último, el estudio de la relación existente entre los censos de cocolitóforos en muestras de sedimento superficial procedentes del mar Mediterráneo occidental y las variables ambientales asociadas a su columna de agua ha permitido el desarrollo de una función de transferencia para la reconstrucción cuantitativa de la salinidad marina superficial (SMS) a alta resolución para los últimos 25 ka en el mar de Alborán. La evaluación estadística del modelo de regresión y calibración y la comparación de la reconstrucción obtenida con otros registros de SMS localizados en la zona de estudio demuestran el elevado potencial de los cocolitóforos en funciones de transferencia para realizar reconstrucciones ambientales cuantitativas. La función de transferencia obtenida se propone como un nuevo indicador para reconstruir la variabilidad de la SMS a partir de asociaciones cocolitoforales fósiles de otros testigos sedimentarios del mar Mediterráneo occidental, especialmente para los últimos 15 ka.

[EN] This Thesis is a high resolution micropaleontological study of the IODP Site U1314, recovered during the IODP 306 Expedition, in the Gardar Drift formation (southern Iceland), in the subpolar North Atlantic. The main purpose of this Thesis is the study of climatic variations at different time scales (orbital and suborbital) and the evolution of surface circulation patterns in the North Atlantic through changes in the associations of cocolitophorids that occurred during the interval between 1,050,000 and 400,000 years (MIS 30-11); known as the Middle Pleistocene Transition. The reason for studying the coccolitophorids assemblages’ variations is due to the fact that they conform one of the main components of the phytoplankton in the current oceans. These organisms secrete calcified plaques (cocoliths) that, after sedimentation in the seabed, can be preserved in the fossil record. Coccolithophore abundance and diversity are highly influenced by the environmental conditions that prevailed at time these organisms inhabited the ocean. Hence, the study of coccoliths preserved in the sedimentary record provides useful information to perform paleoenvironmental reconstructions. In this Doctoral Thesis, a record of calcareous nanofossils has been analyzed in the interval from MIS 11 to 30. In addition, statistical and mathematical analyses of the calcareous nanofossils assemblage, especially the spectral analysis and the analysis of delays between different variables (LAG), have been made in order to know the responsetime between two systems (or sites) affected by the same climatic effect. We have also compare our study with site MD03-2699 (southern of site U1314), with the aim of reconstructing how and when the NAC (North Atlantic Current) could vary in the MIS 11-14 interval. The importance of this study, located in the North Atlantic and specifically the subpolar North Atlantic, is related to the sensitivity of the area to climatic and oceanographic changes. The surface oceanographic regime is strongly imprinted by the Subpolar gyre, specifically by the NAC, which feeds the IC (Irminger Current). When the NAC and the IC arrive at high latitudes, they will sink generating deep waters masses. Oceanographic changes at deep waters are important in this area because it is a deepwater formation zone (Labrador Sea and Norwegian Sea-Greenland), which is the motor of the thermohaline circulation and affect the global circulation. The calcareous nanofossils asemblages showed abrupt changes between the warm interval assemblage, where the total abundance of species is greater and dominated by the species associated to the IC and the cold interval assemblage where the total abundance is low and the species associated with waters of the IC abruptly decline. These abrupt changes are due to the latitudinal variation of the NAC waters and the cold waters from farther north, which ultimately determine the position and variation of the IC waters. This variation of the waters throughout the study interval allows us to reconstruct four scenarios of surface water circulation: High advection of the Irminger waters, low advection of the Irminger water, advection of polar water and terminations. The analysis of the cyclicity of the different records elaborated in this Thesis has shown that the associations of nanofossils have been affected by the three orbital parameters: eccentricity, obliquity and precession, which have allowed to observe a progressive increase in the importance of the precession in the climate cycles, which could affect the insolation on the sea surface, which ultimately affected the position of the ocean currents., [ES] El estudio de los eventos climáticos abruptos y de los mecanismos implicados representan uno de los mayores retos a los que se enfrenta la investigación climática hoy en día. La identificación de los mecanismos de retroalimentación entre los sistemas océano- atmósfera-criosfera son de vital importancia para la comprensión de la variabilidad climática presente en registros sedimentarios del fondo oceánico. Entender cómo y por qué ocurrieron los cambios climáticos del pasado nos puede ayudar a predecir futuros escenarios relacionados con cambios climáticos. En esta Tesis se aportan nuevos datos y enfoques sobre los cambios climáticos y oceanográficos que se registraron entre aproximadamente 1,050,000 y 400,000 mil años en las latitudes altas del Atlántico Norte y que se relacionan con el clima y la circulación oceánica global. El Atlántico Norte subpolar está considerado como una de las regiones climáticas más sensibles de la Tierra y es la llave fundamental para la compresión de la de la circulación de retorno (AMOC) en el Atlántico. Las variaciones de los parámetros superficiales influyen en la circulación y en la formación de masas de agua profundas, explicando por qué las variaciones entre periodos glaciares e interglaciares afectan a la formación de agua profunda, a cómo el calor se distribuye en el océano y a la distribución vertical de nutrientes que afectan a las comunidades planctónicas. El intervalo de tiempo estudiado en esta Tesis Doctoral está caracterizado por la asimetría en los ciclos climáticos y contiene la llamada “transición del Pleistoceno medio”, entre los 1.1 y 0.6 Ma, caracterizados por una reorganización climática que se ha registrado en sedimentos marinos y continentales y se caracteriza por cambios a nivel global, entre los cuáles se incluyen cambios en temperatura del mar, nivel del mar y masas de hielo y afectó a la distribución y evolución de la vida en la Tierra, incluyendo a los ancestros de los seres humanos modernos. Durante la primera parte del intervalo de estudio, predominan los ciclos de ~100 ky que habían surgido entre los 950-900 ka mostrando un aumento progresivo en la intensidad de los periodos glaciales, produciéndose grandes acumulaciones de hielo en el hemisferio norte. Sin embargo, no es hasta aproximadamente los 400 ka (durante el periodo llamando “Evento Mid-Brunhes”) cuando los ciclos de ~100 ka adquieren su mayor amplitud, caracterizándose por periodos glaciales muy fríos e interglaciales muy cálidos. Dada la estrecha relación entre hidrosfera y criosfera, esta reconfiguración del volumen de hielo global tuvo gran repercusión en los patrones de circulación oceánica superficial y profunda a nivel global y muy especialmente en la región del Atlántico Norte. Establecer cuáles son los mecanismos de retroalimentación implicados en esta reconfiguración del sistema climático a escala orbital y suborbital representa uno de los grandes retos de la paleoclimatología moderna que se trataran en esta Tesis. El trabajo presentado se basa en el análisis de una secuencia sedimentaria del sondeo marino profundo U1314, perforado en la formación Gardar Drift (sur de Islandia), durante la Expedición 306 del Integrated Ocean Drilling Program (IODP) en el Atlántico Norte subpolar. El material recuperado proporciona un registro de alta resolución del intervalo comprendido entre 1.050.000 y 400.000 años.

[ES] El primer trabajo presentado en esta tesis tiene como objetivo principal describir la composición de las asociaciones de los flujos diatomeas en el Mediterraneo Noroccidental, así como sus patrones generales de distribución estacional. Un segundo estudio de este manuscrito es el del análisis de la variabilidad estacional e interanual de los flujos de diatomeas, cocolitos y de material en la estación de Planier en el golfo de León. El último apartado de esta tesis está dedicado al estudio de los foraminíferos planctónicos., [EN] The first work presented in this thesis aims to describe the main composition of diatom associations flows in the northwestern Mediterranean, as well as general patterns of seasonal distribution. A second study of this manuscript is the analysis of seasonal and interannual variability of the fluxes of diatoms, coccoliths and equipment in the station family planning in the Gulf of Lions. The last part of this thesis is dedicated to the study of planktonic foraminifera.

[EN] In this work I reconstruct past sea surface water conditions on the SW Iberian Margin by analysing planktonic foraminifer assemblages from IODPSite U1 (37º34.285´N,10º7.562´W;2585mdepth).The data provide a continuous climate record from Marine Isotope Stages (MIS) 21 to 13,extending the existing paleocli recorothIberian Margin back to the ninth climatic cycle (867 ka)., [ES] En esta tesis se reconstruyen las condiciones paleoceanográficas superficiales en el margen occidental ibérico mediante el análisis de las asociaciones de foraminíferos planctónicos de sedimentos procedentes del testigo IODP-U1385 (37º34.285´N, 10º7.562´W; 2585 m de profundidad). Los datos proporcionan un registro climático continuo y de alta resolución para los estadios isotópicos marinos (MIS) 21 a 11, ampliando el registro existente del margen ibérico hasta el noveno ciclo climático (867 ka).

[EN] Coccolithophores are calcareous unicellular algae that play an important role in the carbon cycle because they take carbon from the surface waters during the photosynthesis and the calcification and transfer it to the deep ocean. Hence, they are key actors in the regulation of the rate of CO2 exchange between the atmosphere and the ocean, and therefore, in the global climate change. This thesis presents studies on coccolith geochemistry and morphometry from cores MD95-2043 and MD03-2705 retrieved from the Alboran Sea and off Mauritania respectively. The Alboran Sea is the westernmost basin of the Mediterranean Sea, and therefore, the direct link with the Atlantic. The interaction with the Atlantic waters makes it one of the most productive areas within the Mediterranean, moreover, as a semienclosed basin, is particularly sensitive to the climatic changes occurring at the mid-latitude regions. Alternatively, the northwest African coast is a highly productive region where NE trade winds induce a coastal upwelling whereas eolian supplies from the nearby Sahara fertilize the surface waters. In both sites, the climatic and paleoceanographic conditions are controlled by the seasonal latitudinal migrations of the Intertropical Convergence Zone (ITCZ)., [ES] Los cocolitóforos son algas calcáreas unicelulares que juegan un importante papel en el ciclo del carbono ya que toman carbono de las aguas superficiales durante la fotosíntesis y la calcificación y lo transfieren al océano profundo. Por ello, los cocolitóforos son actores clave en la regulación de la tasa de intercambio de CO2 entre la atmósfera y el océano, y por tanto, en el cambio climático global. Esta tesis presenta estudios sobre geoquímica y morfometría en cocolitos de los testigos MD95-2043 y MD03-2705, recuperados del mar de Alborán y la costa de Mauritania, respectivamente. El mar de Alborán es la cuenca más occidental del mar Mediterráneo, y por ello, la conexión directa con el Atlántico. La interacción con aguas atlánticas hace que este mar sea una de las áreas más productivas del Mediterráneo, además, al ser una cuenca semicerrada, presenta una sensibilidad particular a los cambios climáticos que ocurren en regiones de latitudes medias. Por otra parte, la costa noroccidental africana es una región altamente productiva donde los vientos alisios del noreste inducen la aparición de una surgencia costera mientras que los aportes eólicos desde el cercano Sáhara fertilizan las aguas superficiales. En ambas regiones, las condiciones climáticas y paleoceanográficas están controladas por el ciclo estacional de migraciones latitudinales de la Zona de Convergencia Intertropical (ZCIT).

[EN] The Mediterranean-Atlantic gateway connection plays a major role in ocean circulation. In the past during the Messinian Salinity Crisis (MSC; 5.33-5.97 Ma), water exchange between the Mediterranean Sea and the open Atlantic Ocean became restricted or intermittently absent, resulting in extensive evaporitic deposits in Mediterranean Basins. The Miocene-Pliocene boundary marks the re-establishment of Mediterranean-Atlantic exchange through the Gibraltar Strait and once exchange was initiated, Mediterranean Outflow water (MOW) developed. This thesis integrates multi-proxy records of MOW outside the Mediterranean Sea in the Gulf of Cadiz to study the termination, initiation and development of Mediterranean Outflow during the late Miocene to early Pliocene. The initiation and development of MOW was investigated in Integrated Ocean Drilling Program (IODP) Hole U1387C from 731.20 to 865.85 m below seafloor (mbsf), which is located on the upper slope in the Gulf of Cadiz (559 m water depth). Combining bio-, magneto-, and cyclostratigraphy, an age model was constructed with a time interval from about 5.0 to 5.7 Ma. The Miocene-Pliocene boundary at ~826 mbsf in this Hole is associated with a distinct and abrupt change in depositional environment. During the latest Messinian, hemipelagic sediments exhibit precession-induced carbonate cycles, in which the largest quantity of detrital input are found during Northern Hemisphere insolation minima. These cyclic patterns are likely to result from terrigenous input to the basin, while during insolation maxima, more widespread vegetation cover reduced riverine sediment load. There are no indications of bottom water currents or any other strong influence of MOW in stable isotopes or XRF scanning data in Hole U1387C during the late Miocene. Consequently, it is thought that MOW was absent or severely restricted during this time period. Just above the Miocene-Pliocene boundary, two contouritic bigradational sandy-beds and an increase and more variable XRF core scanning Zr/Al ratios with respect to the underlying sediment, indicate the activity of processes related to particle sorting. This provides the earliest evidence for the onset of bottom water current flow immediately at or just above the Miocene-Pliocene boundary. During the Pliocene, strong coupling between sedimentary variations and benthic stable isotope suggest the influence of bottom waters on the stable isotopes. When bottom water currents are stronger, stable isotopic expressions with similar values as in Hole U1387C are found in the Mediterranean benthic foraminiferal record from the Capo Rosello sections (Sicily, Italy), characterized by well-ventilated, warmer waters. However, bottom water currents are repeatedly interrupted, as indicated with more aluminosilicate rich beds with smaller grain sizes. During these intervals, benthic stable isotopes do not match the Mediterranean record, but record the influence of a colder and poorly ventilated water mass likely to derive from the Atlantic. Remarkably, sea surface d18O and relative abundances of planktic foraminifers Globigerinoides record coeval transitions, but in the opposite direction; when bottom waters become cold, warming is observed at surface. This pattern can be attributed to short episodes of estuarine circulation in the Mediterranean Sea, forcing Atlantic Inflow water over the sill of the Gibraltar Strait at depth while MOW exited at surface. Such a circulation pattern can be triggered by lower water densities at surface in the Mediterranean, what can be triggered by a heat balance that is less negative and a fresher net water budget. Alternatively, a three-layer flow through the gateway or a vertical shift of the MOW-plume towards shallower depths may have caused the observed pattern in the Gulf of Cadiz, although, the latter does not explain the quick synchronous shifts in the benthic stable isotopes with sea surface records. The origin of bottom water masses in the Gulf of Cadiz was also investigated through the use of authigenic neodymium (Nd) and lead (Pb) isotopes. Isotope ratios of Ferro-Manganese (Fe-Mn) oxyhydroxide sediment leachates of Hole U1387C are compared to ratios in sediments leachates of the Alboran Sea and in three Fe-Mn crusts of different water depths in the NE Atlantic (Abouchami et al., 1999; Muiños et al., 2008), to investigate endmember compositions of MOW and NE Atlantic water during the late Miocene to early Pliocene. Authigenic isotope ratios seem to correspond to oceanographic and deposistional settings, however, it remains unclear what exactly controls the incorporated authigenic signal. The isotopic Nd imprint does not match any endmember isotopic signatures as recorded in the Fe-Mn crusts. Therefore, this record is interpreted as mainly controlled by local processes, best explained by the release of rare earth elements with accompanied Nd isotopic compositions from suspended detrital sediments. Pb isotope ratios in the Alboran Sea sediments and NE Atlantic Fe-Mn crusts interpretations are incompatible. If however, the sediment leachate samples from the Alboran Sea provide reliable Pb isotopic compositions for MOW, then the leachate compositions match the stable isotope interpretations. This hints towards the usability of Fe-Mn oxyhydroxide Pb isotopic compositions as a reliable bottom water tracer in the marginal settings of the Gulf of Cadiz. Mediterranean-Atlantic water exchange before the MSC took place through the Betic Corridor in southern Spain and the Rifian Corridor in North West Morocco. These two gateways ceased during the late Miocene, but the actual timing of the closure of these Corridors has been under debate (Flecker et al. 2015). In the western Betic Cordilleras, upper Miocene basins nearby Ronda, Antequera and Arcos de la Frontera are adjacent to the late Miocene Guadalhorce Corridor, which has previously been described as the last remaining branch of the Betic Corridor (Martín et al., 2001). Sedimentary sequences in these basins are characterized by a transition from deeper marine sandy marls to shallow marine calcarenites or limestones. Biostratigraphic analyses of the marls indicate an age of deposition before 7.58 Ma. The overlying calcarenites and limestones were not reliably dated due to the lack of adequate material, however, based on the typical high sedimentation rates of these deposits, it seems unlikely that the calcarenites and limestones are much younger than the marls. This implies that the Guadalhorce Corridor is likely to have closed during the late Tortonian or early Messinian and thus cannot have supplied the necessary water to the Mediterranean to develop the extensive evaporite deposits. Considering similarities in timing and lithological successions, the shallowing upward sequences are linked to the same tectonic pulse that closed the remaining branches in the eastern Betics.

[EN] The Mediterranean-Atlantic gateway connection plays a major role in ocean circulation. In the past during the Messinian Salinity Crisis (MSC; 5.33-5.97 Ma), water exchange between the Mediterranean Sea and the open Atlantic Ocean became restricted or intermittently absent, resulting in extensive evaporitic deposits in Mediterranean Basins. The Miocene-Pliocene boundary marks the re-establishment of Mediterranean-Atlantic exchange through the Gibraltar Strait and once exchange was initiated, Mediterranean Outflow water (MOW) developed. This thesis integrates multi-proxy records of MOW outside the Mediterranean Sea in the Gulf of Cadiz to study the termination, initiation and development of Mediterranean Outflow during the late Miocene to early Pliocene. The initiation and development of MOW was investigated in Integrated Ocean Drilling Program (IODP) Hole U1387C from 731.20 to 865.85 m below seafloor (mbsf), which is located on the upper slope in the Gulf of Cadiz (559 m water depth). Combining bio-, magneto-, and cyclostratigraphy, an age model was constructed with a time interval from about 5.0 to 5.7 Ma. The Miocene-Pliocene boundary at ~826 mbsf in this Hole is associated with a distinct and abrupt change in depositional environment. During the latest Messinian, hemipelagic sediments exhibit precession-induced carbonate cycles, in which the largest quantity of detrital input are found during Northern Hemisphere insolation minima. These cyclic patterns are likely to result from terrigenous input to the basin, while during insolation maxima, more widespread vegetation cover reduced riverine sediment load. There are no indications of bottom water currents or any other strong influence of MOW in stable isotopes or XRF scanning data in Hole U1387C during the late Miocene. Consequently, it is thought that MOW was absent or severely restricted during this time period. Just above the Miocene-Pliocene boundary, two contouritic bigradational sandy-beds and an increase and more variable XRF core scanning Zr/Al ratios with respect to the underlying sediment, indicate the activity of processes related to particle sorting. This provides the earliest evidence for the onset of bottom water current flow immediately at or just above the Miocene-Pliocene boundary. During the Pliocene, strong coupling between sedimentary variations and benthic stable isotope suggest the influence of bottom waters on the stable isotopes. When bottom water currents are stronger, stable isotopic expressions with similar values as in Hole U1387C are found in the Mediterranean benthic foraminiferal record from the Capo Rosello sections (Sicily, Italy), characterized by well-ventilated, warmer waters. However, bottom water currents are repeatedly interrupted, as indicated with more aluminosilicate rich beds with smaller grain sizes. During these intervals, benthic stable isotopes do not match the Mediterranean record, but record the influence of a colder and poorly ventilated water mass likely to derive from the Atlantic. Remarkably, sea surface d18O and relative abundances of planktic foraminifers Globigerinoides record coeval transitions, but in the opposite direction; when bottom waters become cold, warming is observed at surface. This pattern can be attributed to short episodes of estuarine circulation in the Mediterranean Sea, forcing Atlantic Inflow water over the sill of the Gibraltar Strait at depth while MOW exited at surface. Such a circulation pattern can be triggered by lower water densities at surface in the Mediterranean, what can be triggered by a heat balance that is less negative and a fresher net water budget. Alternatively, a three-layer flow through the gateway or a vertical shift of the MOW-plume towards shallower depths may have caused the observed pattern in the Gulf of Cadiz, although, the latter does not explain the quick synchronous shifts in the benthic stable isotopes with sea surface records. The origin of bottom water masses in the Gulf of Cadiz was also investigated through the use of authigenic neodymium (Nd) and lead (Pb) isotopes. Isotope ratios of Ferro-Manganese (Fe-Mn) oxyhydroxide sediment leachates of Hole U1387C are compared to ratios in sediments leachates of the Alboran Sea and in three Fe-Mn crusts of different water depths in the NE Atlantic (Abouchami et al., 1999; Muiños et al., 2008), to investigate endmember compositions of MOW and NE Atlantic water during the late Miocene to early Pliocene. Authigenic isotope ratios seem to correspond to oceanographic and deposistional settings, however, it remains unclear what exactly controls the incorporated authigenic signal. The isotopic Nd imprint does not match any endmember isotopic signatures as recorded in the Fe-Mn crusts. Therefore, this record is interpreted as mainly controlled by local processes, best explained by the release of rare earth elements with accompanied Nd isotopic compositions from suspended detrital sediments. Pb isotope ratios in the Alboran Sea sediments and NE Atlantic Fe-Mn crusts interpretations are incompatible. If however, the sediment leachate samples from the Alboran Sea provide reliable Pb isotopic compositions for MOW, then the leachate compositions match the stable isotope interpretations. This hints towards the usability of Fe-Mn oxyhydroxide Pb isotopic compositions as a reliable bottom water tracer in the marginal settings of the Gulf of Cadiz. Mediterranean-Atlantic water exchange before the MSC took place through the Betic Corridor in southern Spain and the Rifian Corridor in North West Morocco. These two gateways ceased during the late Miocene, but the actual timing of the closure of these Corridors has been under debate (Flecker et al. 2015). In the western Betic Cordilleras, upper Miocene basins nearby Ronda, Antequera and Arcos de la Frontera are adjacent to the late Miocene Guadalhorce Corridor, which has previously been described as the last remaining branch of the Betic Corridor (Martín et al., 2001). Sedimentary sequences in these basins are characterized by a transition from deeper marine sandy marls to shallow marine calcarenites or limestones. Biostratigraphic analyses of the marls indicate an age of deposition before 7.58 Ma. The overlying calcarenites and limestones were not reliably dated due to the lack of adequate material, however, based on the typical high sedimentation rates of these deposits, it seems unlikely that the calcarenites and limestones are much younger than the marls. This implies that the Guadalhorce Corridor is likely to have closed during the late Tortonian or early Messinian and thus cannot have supplied the necessary water to the Mediterranean to develop the extensive evaporite deposits. Considering similarities in timing and lithological successions, the shallowing upward sequences are linked to the same tectonic pulse that closed the remaining branches in the eastern Betics.

[ES] Se analizaron las asociaciones de foraminíferos bentónicos y planctónicos, así como indicadores geoquímicos de un testigo (PRGL 1) extraído en la parte alta del talud continental del Golfo de León (Mediterráneo Occidental), durante la campaña PROMESS I, con el objetivo de reconocer el impacto de los cambios climáticos y del nivel del mar desde 133 ka a 400 ka. Las asociaciones de foraminíferos bentónicos respondieron a cambios en el nivel del mar que a su vez controlaban la distancia de la desembocadura del río Ródano. Asimismo, se reconocieron episodios de ventilación en el fondo mediante especies adaptadas a condiciones óxicas. Por su parte las asociaciones de foraminíferos planctónicos respondieron a cambios en la temperatura de la columna de agua desarrollándose las especies más cálidas, asociadas a masas de agua estratificadas, durante los interglaciares y las más frías, asociadas a una mayor mezcla vertical, en los glaciales. Además, se constataron diferencias en la productividad primaria durante los periodos glaciales. Paralelamente, se estudió la relación C/N en materia orgánica y el contenido de CaCO3, Sr, Fe, Al, K, Ti y P en sedimento. Durante los mínimos de precesión la estratificación termal de la columna de agua provocó que las condiciones en el fondo dependieran de la proximidad del río Ródano. En los periodos con bajo nivel del mar las condiciones eutróficas prevalecieron y el sedimento presentó altas proporciones de CaCO3 de origen detrítico procedente de los Alpes, sin embargo durante los niveles del mar alto, debido al alejamiento de la desembocadura del Ródano las condiciones del fondo cambiaron a mesotróficas y el sedimento estuvo principalmente compuesto de CaCO3 de origen biogénico. Durante los máximos de precesión, las entradas recurrentes de aire polar, incrementaron la densidad del agua provocando fenómenos recurrentes de hundimiento y ventilación del fondo, [EN] In the present study we analyzed benthic and planktic foraminifer assemblages, as well as geochemical indicators of the core PRGL 1 retrieved at the upper slope of the Gulf of Lions (Western Mediterranean), during PROMESS I campaign, in which the goal was to monitor the impact of climatic changes and sea level between 133 kyr and 400 kyr.The benthic foraminifera responded to changes in sea level, which in turn controlled the distance from the mouth of the Rhone River. Also recognized episodes vent at the bottom by species adapted to oxic conditions. Meanwhile the planktonic foraminifera responded to changes in the temperature of the water column species develop warmer associated with stratified water bodies during the interglacial and colder associated with increased vertical mixing in the glacial . Also showed differences in primary productivity during glacial periods. In parallel, we studied the C / N in organic matter and CaCO3 content, Sr, Fe, Al, K, Ti and P in sediment. During the precession minimum thermal stratification of the water column led bottom conditions to depend on the proximity of Rhone mouth. During lowstands eutrophic conditions prevailed and sediment CaCO3 showed high proportions of detrital origin from the Alps, however during high sea levels, due to the remoteness of the mouth of the Rhone bottom conditions changed to mesotrophic and the sediment was mainly composed of biogenic CaCO3. During the peak of precession, air tickets polar recurring increased the density of water causing recurring phenomena of collapse and ventilation fondo

[EN] In this PhD thesis, we contribute to a more detailed knowledge of the biogeography of coccolithophores in one of the most productive marine ecosystem on earth: the Peru-Chile Current realm, which extends along the west coast of South America., [ES] En esta tesis se contribuye a un mayor conocimiento de la biogeografía de los Cocolitóforos en uno de los ecosistemas marinos más productivos de nuestro planeta: el sistema de corrientes de Perú- Chile, que se extiende a lo largo de la costa oeste de Suramérica.

[ES]Esta Tesis Doctoral está enfocada al estudio de la variabilidad temporal y espacial de la señal de paleoproductividad y la topografía de la nutri-termoclina durante los últimos ciclos climáticos en los océanos Pacífico oriental y Atlántico occidental tropicales. Los mecanismos hidrológicos y atmosféricos que controlan estas señales están relacionados con la activación de las células de surgencia, la dinámica de las corrientes superficiales y subsuperficiales, la migración del frente ecuatorial y el desplazamiento latitudinal de la zona de convergencia intertropical ( Intertropical Convergence Zone ITCZ).En este estudio se analizó cuantitativamente la distribución temporal y espacial de las asociaciones de cocolitóforos y del carbonato asociado a estos organismos en las secuencias sedimentarias 1240 (estadios 15 a 1), 1241 (estadios 20 a 1) y 1242 (estadios 22 a 1), extraídas por el proyecto Ocean Drilling Program (ODP) 202 en el océano Pacífico oriental tropical. Adicionalmente se analizó la secuencia MD03-2616 (estadios 6 a 1) recuperada en la campaña PICASSO Cruise en el océano Atlántico occidental tropical. En términos generales, los sedimentos están compuestos principalmente por arcillas hemipelágicas con cantidades variables de nanofósiles calcáreos, foraminíferos, diatomeas y terrígenos, si bien los nanofósiles calcáreos son habitualmente el componente biogénico principal (Mix et al., 2003). Aunque algunos intervalos se caracterizan por una preservación deteriorada en los testigos 1242 y MD03-2616, tratando de enmascarando un poco el significado micropaleontológico de los perfiles de paleoproductividad y del carbonato derivado de los cocolitos, la preservación general de los ejemplares estudiados es buena a moderada, y realza el significado micropaleontológico de estos registros en todos los testigos estudiados., This PhD Thesis is focused on the study of the temporal and spatial variability of the paleoproductivity record, the nutri-thermocline topography and all the mechanisms associated to them in the Eastern Tropical Pacific (ETP) and the Western Tropical Atlantic (WTA) over the lastclimatic cycles. These mechanisms are related to the strengthening of the upwelling cells, the dynamic of the surface and subsurface currents, the migration of the Equatorial Front and the latitudinal displacement of the Intertropical Convergence Zone (ITCZ). The purpose was carried out through the analysis of the calcareous nannoplankton assemblage along the sedimentary sequences from the Ocean Drilling Program (ODP) Leg 202, sites 1240 (Marine Isotope Events MIS 15 to 1), 1241 (MIS 20 to 1) and 1242 (MIS 22 to 1) recovered from the ETP. The calcareous nannoplankton assemblage from core MD03-2616 was also studied for paleoceanographical purposes along MIS 6 to 1. This last sequence was recovered by the PICASSO Cruise in the WTA. Sediments mostly consist of hemipelagic clays with variable amounts of calcareous nannofossils, foraminifers, diatoms and terrigenous matter, being the calcareous nannofossils the primary biogenic component (Mix et al., 2003). Although several intervals are characterized bydeteriorated carbonate preservation at sites 1242 and MD03-2616, masking the micropaleontological signal, the overall preservational pattern varies between good and moderate, enhancing the micropaleontological significance of all the records studied.

[EN]Foraminifer assemblages and geochemistry from ODP site 977A (Alboran Sea) and PRGL1-4 (Gulf of Lions) have been studied to analyse changes in the microfauna, climate and paleoceanography in the Western Mediterranean Sea at several time intervals during the last 250 kyr. The planktonic foraminifer assemblages in the Alboran Sea seem to be mainly controlled by changes in sea surface temperature (SST) and confirm the pervasive millennial variability previously reported with alkenone-based SST. In addition, astronomical variability is also shown by the foraminifer assemblages. The warm substages of stage 7 are recognized by the high abundances of the species Globigerinoides ruber, reflecting oligotrophic conditions and a stratification of the water column, coinciding with the Northern Hemisphere summer insolation maxima. Water stratification is due to surface water warming (density decrease) and coincides with strong seasonality. These oceanographic conditions gradually changed to more vertical mixing and weaker seasonality during cold substages. Neogloboquadrina pachyderma (left coiling) is very scarce during the period studied, suggesting a reduced southward influence of the Polar Front and less extreme cooling at that time. Several possible Heinrich-like events are described in this study. These periods of iceberg discharges from the North Atlantic are recorded in the Mediterranean Sea by low water δ18O values, low salinity, relatively low SST, a decrease in the total number of planktonic foraminifers, and disappearance of Globorotalia inflata and temperate water species. These lighter oxygen isotope and low salinity waters would have caused density stratification. The extremely cold conditions caused an abrupt and drastic decrease in surface productivity. During the period studied four organic-rich layers (ORL) can be recognized. These sediments are related to the sapropels from the Eastern Mediterranean. It may be observed that all the organic-rich layers coincide with low δ18O values in Globigerina bulloides. This relates the formation of these layers to the arrival of isotopically lighter waters. The origin could have been either increased rainfall over the Mediterranean area or a stronger influence of Atlantic waters due to greater inflow to the Mediterranean. The geochemical data suggest that they were formed under stratification conditions and at times of high surface productivity. No organic-rich layer was developed during the 220 kyr-Northern Hemisphere summer insolation maximum due to the occurrence of a possible Heinrich-like event at the same time, however sapropel 8 was formed, suggesting that different factors affect the Mediterranean subbasins in a different way. A reconstruction of SST in the Alboran Sea between 245 and 145 kyr has been made based on the modern analog technique using planktonic foraminifers. We used a modern database that contains a total of 253 samples, 123 from the North Atlantic and 130 from the Mediterranean Sea. For the estimates we used PaleoAnalogs 2.0, computer program developed by the University of Salamanca. Our reconstruction shows a small SST difference between substages 7.3, 7.2 and 7.1. An important millennial variability (7.4, 5.6 and 4.6 kyr) occurs during the whole studied period, both in warm and cold intervals, although changes seem to have more amplitude during cold ones. Seasonality seems to be higher during the warmer substages, 7.5 and 7.3, and smaller during the cold substage 7.4. Mg/Ca paleothermometry and stable isotope measurements performed on tests from the planktonic foraminifers Globigerinoides ruber (white), Globigerina bulloides, and Neogloboquadrina pachyderma (right coiling) have revealed that during marine isotope stages 6 and 7 warm substages were characterized by strong seasonality, thermal stratification of the water column and less surface productivity. By contrast, during cold substages less pronounced seasonality and basin stratification prevailed together with greater productivity. These data also revealed that periods of stratification due to the low salinity of the upper water mass occurred during the formation of organic-rich layers and also during Heinrich-like events. Changes in the benthic foraminifer assemblage (at 200 m depth) between 60-30 kyr have been studied in core PRGL1-4 (Gulf of Lions), and have been found to be strongly controlled by the Dansgaard-Oeschger variability. During stadials, the species most represented were Trifarina angulosa, Astrononion gallowayi, Lobatula lobatula, and miliolids; whereas during interstadials, the assemblage was dominated by Hyalinea balthica, bolivinids, buliminids and agglutinated foraminifers. This suggests more oxygenated bottom waters and a lower organic matter content during stadials, as previously seen for the benthic fauna from the Alboran Sea (2000 m depth). This can be explained in terms of enhanced basin-wide vertical mixing caused by stronger winds or of less productivity throughout the Mediterranean basin, due to a reduced nutrient supply from river discharges. However, during interstadials, both weaker winds and warmer surface waters could have reduced the vertical mixing or a greater nutrient input could have caused an increase in basin productivity. The benthic fauna during Heinrich stadials suggests a similar oceanographic setting to that of the other stadials. In order to better constrain the factors controlling the calcification rate in planktonic foraminifera, and to assess shell weight reliability as an atmospheric CO2 proxy, changes in shell weight in several planktonic foraminifer species (Globigerina bulloides, Neogloboquadrina pachyderma (right coiling) and Globigerinoides ruber (white)) have been studied in core samples from the Alboran Sea (Western Mediterranean) between 250-160 kyr (marine isotope stages 6 and 7). These results suggest that factors controlling calcification rate depend on the species and it is not always related with atmospheric CO2. In Globigerina bulloides and Globigerinoides ruber (white) calcification rate is mainly controlled by atmospheric CO2 and water temperature, whereas Neogloboquadrina pachyderma (right coiling) shell weight is directly related to optimum growth conditions: heavier shell weights coincide with more relative abundance of this species due to optimum temperature conditions. Therefore, foraminifer shell weight should be used carefully as an atmospheric CO2 proxy. Furthermore, Sr/Ca analysis in shells of the same three species of foraminifers were also performed in order to observed interspecific variations and to find out the parameters that control this ratio. Our results show a common, large Sr/Ca variability for the three species studied, thus suggesting changes in the global ocean Sr/Ca ratio as the main cause of variations in shell composition., [ES]Se han estudiado las asociaciones de foraminíferos planctónicos y la geoquímica en muestras del mar de Alborán y el golfo de León) para analizar los cambios en la microfauna, el paleoclima y la paleoceanografía en el Mediterráneo occidental durante los últimos 250 ka. Las asociaciones de foraminíferos planctónicos en el mar de Alborán parecen haber estado controladas principalmente por cambios en la temperatura del agua superficial (SST), lo que confirma la variabilidad milenaria observada en anteriores estudios. Varios posibles eventos Heinrich tuvieron lugar causaron un drástico y rápido descenso en la productividad superficial y una estratificación de la columna de agua por densidad. Además, se han reconocido cuatro capas ricas en materia orgánica cuya formación se relaciona con la llegada de aguas isotópicamente más ligeras causada por un aumento en las precipitaciones sobre la región mediterránea o una mayor influencia de las aguas atlánticas debido a un mayor intercambio a través del estrecho de Gibraltar bajo condiciones de estratificación de la columna de agua y alta productividad superficial. Se han reconstruido las SST en el mar de Alborán basadas en el método de los análogos modernos aplicado a los foraminíferos planctónicos y utilizando la relación Mg/Ca. Ambos resultados son similares aunque la relación Mg/Ca presenta ciertas ventajas. Con el fin de evaluar los factores que controlan la tasa calcificación en los foraminíferos planctónicos y si su peso se puede utilizar como indicador de CO2 atmosférico, se ha estudiado la evolución del peso de los foraminíferos en diferentes especies y parece que dicho parámetro debe ser utilizado con cautela. Finalmente, los cambios en la asociación de foraminíferos bentónicos entre 27 y 57 ka en el golfo de León parecen haber estado controlados fuertemente por la variabilidad milenaria Dansgaard-Oeschger, que pudo haber afectado a la oceanografía de todo el Mediterráneo.