The presence of the sea ice diatom biomarker IP25 in Arctic marine sediments has been used in previous studies as a proxy for past spring sea ice occurrence and as an indicator of wider palaeoenvironmental conditions for different regions of the Arctic over various timescales. The current study describes a number of analytical and palaeoceanographic developments of the IP25 sea ice biomarker. First, IP25 was extracted and purified from Arctic marine sediments. This enabled the structure of IP25 to be confirmed and enabled instrumental (GC-MS) calibrations to be carried out so that quantitative measurements could be performed with greater accuracy. Second, palaeo sea ice reconstructions based on IP25 and other biomarkers were carried out for a suite of sub-Arctic areas within the Greenland, Norwegian and Barents Seas, each of which represent contrasting oceanographic and environmental settings. Further, an evaluation of some combined biomarker approaches (e.g. the PIP25 and DIP25 indices) for quantifying and/or refining definitions of sea ice conditions was carried out. Temporally, particular emphasis was placed on the characterisation of sea ice conditions during the Younger Dryas and the Holocene. Some comparisons with other proxies (e.g. foraminifera, IRD) were also made. A study of a sediment core from Andfjorden (69.16˚N, 16.25˚E), northern Norway, provided unequivocal evidence for the occurrence of seasonal sea ice conditions during the Younger Dryas. The onset (ca. 12.9 cal. kyr BP) and end (ca. 11.5 cal. kyr BP) of this stadial were especially clear in this location, while in a study from the Kveithola Trough (74.52˚N, 16.29˚E), western Barents Sea, these transitions were less apparent. This was attributed to the presence of colder surface waters and the occurrence of seasonal sea ice both before and after this stadial at higher latitudes. Some regional differences regarding the severity of the sea ice conditions were also observed, although an overall general picture was proposed, with more severe sea ice conditions during the early-mid Younger Dryas and less sea ice observed during the late Younger Dryas. A shift in the climate towards ice-free conditions was recorded in northern Norway during the early Holocene (ca. 11.5 – 7.2 cal. kyr BP). Milder conditions were also observed during the Holocene in the western Barents Sea, with three main climate periods observed. During the early Holocene (ca. 11.7 – 9.5 cal. kyr BP), the position of the spring ice edge was close to the study area which resulted in high productivity during summers. During the mid-late Holocene (ca. 9.5 – 1.6 cal. kyr BP), sea ice was mainly absent due to an increased influence of Atlantic waters and northward movement of the Polar Front. During the last ca. 1.6 cal. kyr BP, sea ice conditions were similar to those of the present day. In addition to the outcomes obtained from the Norwegian-Barents Sea region, comparison of biomarker and other proxy data from 3 short cores from Kangerdlugssuaq Trough (Denmark Strait/SE Greenland) with historical climate observations allowed the development of a model of sea ice conditions which was then tested for longer time-scales. It is suggested that the IP25 in sediments from this region is likely derived from drift ice carried from the Arctic Ocean via the East Greenland Current and that two main sea surface scenarios have existed over the last ca. 150 yr. From ca. AD 1850 – 1910, near perennial sea ice conditions resulted in very low primary productivity, while from ca. AD 1910 – 1986, local sea ice conditions were less severe with increased drift ice and enhanced primary productivity. This two-component model was subsequently developed to accommodate different sea surface conditions that existed during the retreat of the Greenland Ice Sheet during the deglaciation (ca. 16.3 – 10.9 cal. kyr BP).

Les données sur la transition tardiglaciaire-holocène (de 14500 a 6000 bp) s'appuient sur les resultats livrés par le gisement de st. Thibaud-de-Couz (Savoie, Chartreuse) et une dizaine de sites à stratigraphies developpées qui ont fait l'objet de fouilles récentes. Ces sites représentent des remplissages karstiques qui permettent d'avoir une vision précise mais ponctuelle sur les modalités du passage du dernier glaciaire à l'interglaciaire actuel. L'approche chronostratigraphique assure les bases chronologiques des évolutions naturelles et culturelles. L'étude d'une douzaine de séquences stratigraphiques a permis de distinguer quelques types d'enregistrement sédimentaire propres à chaque phase de l'évolution climato-sédimentaire. La reconstruction de l'évolution paléoclimatique a été faite selon deux approches complémentaires: 1) la sédimentologie met particulièrement en évidence les manifestations de l'humidité qui sous climat froid engendre une importante sédimentation détritique et sous climat chaud des dépôts carbonatés ; 2) l'étude des faunes de mollusques terrestres permet de préciser les conditions paléoécologiques et climatiques locales ; la présence d'une association à columella de type périglaciaire est significative. Les resultats mettent particulièrement en évidence le caractére instable du climat. Le problème des occupations humaines est abordé a travers l'étude des outillages lithiques sous deux aspects: 1) l'étude pétrographique permet de localiser les gites d'approvisionnement en silex et d'avoir des indications sur les territoires parcourus ; 2) la caractérisation des systèmes culturels est basée sur les séries lithiques considérées en terme d'ensembles structures ; dans ce but une méthode de classement hierarchisé est proposée. Les grandes étapes de l'évolution chronoculturelle sont precisées ; elles sont marquées par de profondes mutations qui caractérisent les cultures de la fin du Paléolithique superieur au Mésolithique et par l'émergence des premieres phases de la néolithisation. Une synthèse intégrant l'ensemble des données bioclimatiques et culturelles permet de proposer un modèle de transition dernier glaciaire-interglaciaire actuel caracterisée par une succession de cycles à régimes climatiques contrastes situés à la charnière de deux périodes à climats plus stables. La mise en parallèle des donnees culturelles suggère une relation forte entre évolutions culturelles et changements bioclimatiques

Comprendre la complexité des relations entre nature et sociétés a toujours constitué un défi pour les recherches dans le domaine de l'environnement. A l'ère de la compilation de données dans de nombreuses disciplines, la modélisation constitue l'une des options les plus attractives pour comprendre et traduire les évolutions du milieu naturel. Les objectifs principaux de ce travail de recherche sont 1) de restituer la structure du couvert végétal régional et d'en retracer les évolutions au cours de l'Holocène au sein de deux régions du nord-ouest de la France, le Bassin parisien et le Massif armoricain, et 2) de les interpréter en termes de relations entre les sociétés pré- et protohistoriques et leur milieu naturel. Pour cela, nous avons mis en place une démarche méthodologique visant à 1) redéfinir le cadre chronologique des séquences polliniques rassemblées pour les deux régions, 2) tester, adapter puis appliquer un modèle de reconstitution quantitative du couvert végétal, 3) définir une histoire de la végétation estimée relative à chaque aire géographique modélisée, 4) comparer ces histoires régionales et 5) les confronter aux informations disponibles en matière de densités de sites archéologiques et de proximité de ces sites aux points de sondages polliniques. Des cadres structurant l'évolution du couvert végétal pour chacune des deux régions étudiées ressortent les grandes étapes de la mise en place des paysages au cours de l'Holocène. Des spécificités régionales ont cependant pu être identifiées, tant en matière de chronologie de l'évolution de la végétation estimée qu'en matière de proportions relatives des taxons présents. Une certaine singularité doit donc être reconnue à l'évolution des paysages holocènes de chacune de ces deux parties du nord-ouest de la France. On remarque notamment des dynamiques et des niveaux d'anthropisation tout à fait distincts entre Bassin parisien et Massif armoricain de la fin du Mésolithique à celle du Néolithique. A l'inverse, on retrouve de part et d'autre une certaine similarité entre les proportions estimées des taxons marqueurs d'anthropisation entre la fin du Néolithique et celle de l'âge du Bronze. Des liens évidents entre les variations de l'impact anthropique enregistré et celles de la densité des occupations reconnues ont par ailleurs pu être observés. / Understanding the complex relationship between nature and societies has always been a challenge for environmental sciences. With the growing impact of databases in many disciplines, the modelling appears as one of the most attractive methods for understanding and describing environmental changes. The main objectives of this research work are 1) to reconstruct the structure of the regional vegetation cover and to determine its trends during the Holocene in two regions of north-western France, the Paris Basin and the Armorican Massif, and 2) to interpret them in terms of relationships between the pre- and proto-historic societies and their environment. Thus, we set up a methodological approach aimed at 1) redefining the chronological framework of pollen sequences collected for both regions, 2) testing, adapting and then applying a model in order to produce quantitative estimates of vegetation cover, 3) defining a history of the estimated vegetation for each area modelled, 4) comparing these regional results and 5) confronting them to the available informations in terms of densities of archaeological sites and proximity of these sites to the pollen samples locations. From the general framework structuring the vegetation cover changes for both study areas stand out the major steps of the development of natural landscapes during the Holocene. Nevertheless, regional distinctive features were identified; both in terms of chronology of the vegetation cover changes, than in terms of relative proportions of taxa in the vegetation estimates. Some singularity must be recognized in the Holocene landscape evolution for each of these two parts of north-western France. We noticed distinct rates and rhythms, concerning the anthropogenic impact on the Paris Basin and the Armorican Massif estimated vegetation covers, from the late Mesolithic to the late Neolithic. On the other hand, we found similarities between both areas concerning the estimated proportions for anthropogenic markers taxa between the late Neolithic and the late Bronze Age. Clear links between changes observed in human impact on the vegetation cover estimates and those recorded in the density of archaeological sites were also noticed.

High-resolution records of early Holocene deposits are rare, and as a consequence reconstruction of terrestrial environments very soon after the deglaciation has often been difficult. In this study the palaeoenvironmental conditions of early Holocene (c. 10600-7500 cal. yr BP) are reconstructed in the Värriötunturit area of northeastern Finland, using evidence from plant macrofossils and pollen preserved in a lake sediment sequence retrieved from the small lake Kuutsjärvi. Special emphasis is put on the environment immediately following the deglaciation as the base of the sediment sequence is rich in minerogenic material interpreted to have been deposited by meltwater pulses from the retreating ice sheet. The abundance and variety of fossil remains in these early meltwater deposits provide evidence for a very productive ice-marginal environment in the area between the lake and the ice sheet, and the presence of tree-type Betula macro remains as well as high percentage values of tree-type Betula pollen suggests that a subarctic birch forest established just a few years after the deglaciation. In the following centuries the birch forest around the lake became rich in an under growth of ferns, and at c. 9400 cal. yr BP a transition into a mixed pine and birch forest took place. Due to absence of indicator plant taxa in the sediment it was not possible to reconstruct temperature conditions for any parts of the sequence in this study. However, the rapid colonisation of birch forests suggests that the climate was warm already during deglaciation, which is also in accordance with climatic conditions reconstructed for the early Holocene in the nearby Sokli area just 10 km away, as well as in other parts of Fennoscandia and Russia.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 1995. / The main concern of this study is the investigation of the events which initiated the symbolic construction of communities in the south-eastern Cape during the Holocene Later Stone Age. To understand and to explain the relationships which existed between different groups in this region a social approach was followed. The data presented in this thesis are a summary of the results obtained from a large number of open-air shell middens, a coastal shelter, Kabeljous River Shelter 1, two coastal caves, Klasies River Caves 1 and 5 along the Cape St Francis coast and The Havens Cave, one of several sites excavated in the adjacent Cape mountains. Lithic evidence from the coastal sites indicates that during the past ·+500 years two distinctly different stone tool industries co-existed side by side along the south-eastern Cape coast. Caves were first occupied between 5800 and 4200 BP by groups with a typical Wilton Industry. At ca 3000 BP the Wilton Indu.rry was 'replaced' in the caves by a macro lithic quartzite cobble industry, named the Kabeljous Industry, but was still present in open-air shell middens until ca 1900 BP. At Klasies River Cave 5 both industries were Pl esent in the cave from 4200 BP to ca 3000 BP. There are no marked differences in the subsistence activities between the two different lithic industries and therefore it is argued that the Kabeljous industry does not reflect technological adaptation to a coastal environment. Instead I argue that the stone tools, as part of material culture production, played an active role in communicating information between groups. Central to the understanding of these social relationships are the concepts of power relations and inclusion. Style was the medium through which groups expressed symbolic group identity and maintained social boundaries. Important however, is the fact that the power rclutinns generated by symbolic identity expression was not aimed at excluding ether groups from their territory, but rather at. inclusion.

Dans le contexte du réchauffement climatique, les enregistrements paléoclimatiques à différentes échelles temporelles et spatiales apparaissent essentiels pour comprendre les mécanismes du climat. La Patagonie Chilienne (41°S à 56°S) parcourue du Nord au Sud par les Andes représente une contrainte topographique majeure sur les circulations atmosphériques et océaniques. Cette région est la seule qui intercepte la totalité de la ceinture des vents d'ouest austraux et constitue donc une zone clé pour étudier les changements paléoenvironnementaux et comprendre les mécanismes océan-atmosphère et leurs interactions aux moyennes et hautes latitudes de l'hémisphère sud. Dans ce contexte, les objectifs de cette thèse sont : (1) de tester l’analyse pollinique dans les sédiments marins de cette région, (2) d’étudier les modifications des paléoenvironnements continentaux au cours des 20 000 dernières années à partir de deux carottes océaniques de la campagne "PACHIDERME" (MD07-3088 et MD07-3104) et (3) de déterminer leurs liens avec l’activité des vents d’ouest et avec l’influence de ces vents dans l’hémisphère sud et donc sur le climat à l’échelle globale. Les analyses polliniques dans les sédiments marins de surface à l’intérieur et à l’extérieur des fjords de la Patagonie reflètent fidèlement la végétation actuelle développée sur le continent le plus proche, ce qui prouve la validité de la palynologie marine dans cette région. Au niveau de la péninsule de Taitao (46°S), l’expansion des forêts nord patagoniennes après 17.6 ka marque le début de la déglaciation. Cette dernière est interrompue par un évènement froid et humide, l’Antarctic Cold Reversal (ACR) qui s’exprime ici par le développement des tourbières de Magellan et est lié à l’intensification des vents d’ouest. Le développement de taxons héliophiles à ~11 ka illustre le début de l’Holocène sous des conditions plus chaudes et plus sèches qui sont également enregistrées autour du Fjord de Reloncavi (41°S). Ces conditions persistent jusqu’à ~8-7 ka, puis les changements de végétation aux cours de l’Holocène montrent une variabilité climatique plus importante évoluant vers un climat plus froid et plus humide qui se renforce au nord de la Patagonie après ~6-5 ka puis pendant l’Holocène supérieur. La comparaison de nos résultats avec les données paléoclimatiques de la région souligne les déplacements de la ceinture des vents d’ouest. Après une descente rapide vers le sud au début de la déglaciation, cette ceinture des vents d’ouest remonte vers le nord pendant l’ACR avant de redescendre à nouveau vers le sud à l’Holocène proche de sa position actuelle. Ce phénomène appuie l’hypothèse d’un lien entre les variations du CO2 atmosphérique et la ceinture des vents d’ouest jusqu’au début de l’Holocène. A partir de l’Holocène moyen et supérieur, la ceinture des vents d’ouest s’élargit avec un léger retour vers le nord probablement lié à la mise en place d’El Niño au niveau de l’océan Pacifique tropical. / In the context of global warming, paleoclimate records at different time and spatial scales appear critical to understand climate mechanisms. Chilean Patagonia (41°S to 56°S), crossed by the Andes from north to south, represents a major topographic constraint on ocean and atmospheric circulation. It is the only region that intercepts the entire southern westerly wind belt. Thus it represents a key-area for the study of paleoenvironmental changes in the southern hemisphere and the understanding of ocean-atmosphere mechanisms and their interactions from the mid- to high-latitudes of the southern hemisphere. In this context, the purposes are: (1) to test the pollen analysis on marine surface sediments in this region, (2) to study the continental changes of paleoenvironments during the last 20,000 years from two oceanic cores of the "PACHIDERME" campaign (MD07-3088 and MD07-3104) and (3) to evaluate their links with southern westerly wind belt activity and with the influence of these winds on the southern hemisphere and with the climate at a global scale. The pollen analyses of marine surface sediments in fjords or offshore from Chilean Patagonia reflect the present-day vegetation from the nearby continental area. At the Peninsula of Taitao (46°S), the North Patagonian forest expansion after 17.6 kyr shows the beginning of the deglaciation. This last (period) is interrupted by a wet and cool event, the Antarctic Cold Reversal (ACR), that was expressed here by development of the Magellanic moorland linked to the southern westerly wind intensification. The expansion of heliophytic taxa at ~11 kyr illustrates the beginning of the Holocene under warmer and drier conditions that are also recorded around the fjord of Reloncavi (41°S). These conditions persisted until ~8-7 kyr, and then the vegetation changes during the Holocene show a larger climate variability toward a cooler and wetter climate that enhances in northern Patagonia later ~6-5 kyr during the Late Holocene. Our results compared with the regional paleoclimatic data highlight the shifts of the southern westerly wind belt. After a rapid southward shift at the beginning of the deglaciation, the southern westerly wind belt returns northward during the ACR before reaching southern latitudes near to their present-day position. This scheme strengthens the inference of the link between atmospheric CO2 variability and the southern westerly wind belt up to the Early Holocene. From the mid and late Holocene, the southern westerly wind belt was displaced northward with a slight return probably linked to the beginning of El Niño recorded in tropical Pacific Ocean.

Neste estudo investigou-se a variabilidade da Monção Sul-Americana (MSA) ao longo dos últimos 38ka, por meio de um registro em alta resolução de \'\'delta\' POT.18\'O baseado em três espeleotemas da caverna Shatuca, localizada no norte do Peru (~ 5ºS). O registro da caverna Shatuca é um dos primeiros registros paleoclimáticos da zona de altitude intermediária no flanco oriental dos Andes setentrionais (1960m). O registro isotópico da Shatuca compreende espeleotemas bem datados e de alta resolução que são usados para investigar a atividade da MSA no passado, em resposta tanto ao ciclo de precessão da insolação, como às mudanças na circulação oceânica, ocorridas durante o último período Glacial - Deglacial, as quais são definidas nos testemunhos marinhos e de gelo do Hemisfério Norte. Os registros de espeleotemas da caverna Shatuca, não mostram nenhum controle claro da insolação sobre a MSA nos Andes entre 38-11 ka AP, o que pode ser explicado por um controle predominante das condições de contorno glaciais sobre a MSA. Mudanças abruptas, entre períodos mais úmidos e mais secos da MSA, em escalas de tempo milenar, são observadas no registro de espeleotemas de Shatuca através de valores de \'\'delta\' POT.18\'O anormalmente baixos e altos, respectivamente. Estes eventos são interpretados como uma resposta aos eventos Heinrich (H) e Dansgaard-Oeschger (D-O) através de deslocamentos latitudinais da Zona de Convergência Intertropical (Intertropical Convergence Zone-ITCZ). No entanto, a intensidade da resposta a esses ciclos foi variável. Em particular, os episódios climáticos mais extremos foram aqueles relacionados aos eventos Heinrich 1 e 2. O período de ocorrência e a estrutura do evento Heinrich 1 (H1) são mais precisamente descritos nos espeleotemas da caverna Shatuca do que em registros anteriores dos Andes e da Bacia de Cariaco. O evento H1 é caracterizado por valores isotópicos baixos entre 18.0 e 14.7 ka AP, o que indica condições predominantemente úmidas; mas um pico, nunca antes registrado, de valores de \'\'delta\' POT.18\'O altos foi registrado em 16.2 ka AP. Este resultado é particularmente importante dado que a ITCZ poderia ter estado deslocada mais ao sul do que 5ºS. Além disso, a estrutura dos períodos do Bølling-Allerød (B/A) e Younger Dryas (YD) assemelha-se à dos testemunhos de gelo da Groenlândia. Durante o Holoceno, o clima da região da caverna Shatuca foi controlado pela insolação, consistente com outros registros de isótopos de diferentes altitudes nos Andes peruanos. O Holoceno Inferior é marcado pelo severo enfraquecimento da MSA na região da Shatuca, sendo seguido por uma tendência de aumento gradual das condições de umidade em direção ao Holoceno Superior, esta tendência climática, em longo prazo, ocorreu em união à tendência de aumento da insolação modulada pelo ciclo de precessão. Condições particularmente úmidas foram sentidas na região da caverna Shatuca após 5.0 ka AP. Várias mudanças abruptas ocorridas, em escalas de tempo centenárias e multidecenais, durante o Holoceno, são descritas pela primeira vez nos Andes. Durante o Holoceno Inferior, o caso mais extremo, é o registrado em 9.5 ka AP, mas outros eventos úmidos ocorreram também, tais como o registrado em 8.1 ka AP. Por outro lado, durante o Holoceno Médio, a comparação com outros registros andinos, na região afetada pela MSA, aponta para uma série de eventos abruptos que ocorreram entre 5.1 e 5.0 ka AP. Finalmente, um resultado importante do presente estudo é a semelhança observada, durante o Holoceno Superior, entre o registro da caverna Shatuca com o do lago Pallcacocha, situado no sul dos Andes equatorianos e amplamente utilizado como um proxy da frequência do fenômeno El Niño Oscilação Sul (El Niño Southern Oscillation -ENSO). O registro Shatuca não apresenta nenhuma evidência clara de ter sofrido algum controle climático influenciado por ENSO. Pelo contrário, propõe-se que ambos registros, o lago Pallcacocha e a caverna Shatuca, indicam um aumento da umidade entre 3.5 e 2.5 ka AP, resultado do controle da alta insolação de verão austral sobre a MSA, e de uma profunda reorganização do sistema climático ocorrido na borda oeste da MSA, entre terras altas e intermediárias dos Andes. / this study, we investigated the South American Summer Monsoon (SASM) variability through the last 38 ky with a high-resolution \'\'delta\' POT.18\'O record based on three speleothems from Shatuca cave, located in northern Peru (~ 5ºS). The Shatuca cave record is one of the first paleoclimate records from mid-altitude (1960m) sites in the northeastern Andean slopes. The Shatuca isotope record comprises well-dated and high-resolution speleothems that were used to investigate the past activity of SASM, in response to both insolation precession cycle and changes in oceanic circulation during the last Glacial-Deglacial period, defined in ice cores and marine core records from the northern Hemisphere. The speleothem records from Shatuca cave show no clear insolation control over the SASM between 38-11 ky BP, which could be explained by a prevailing control of the glacial boundary conditions over SASM. Abrupt millennial shifts between wetter and drier monsoon phases are observed in Shatuca speleothem record based on abnormally low and high values of \'\'delta\' POT.18\'O, respectively. These events are interpreted as a response to Heinrich (H) and Dansgaard-Oeschger (D-O) events through latitudinal displacements in the Intertropical Convergence Zone (ITCZ). However, the response intensity to these events was variable. In particular, the most extreme climate episodes were those related to the Heinrich events 1 and 2. The structure and timing of the Heinrich event 1 (H1) event are more precisely described in Shatuca speleothems than in previous records from Andes and Cariaco Basin. The H1 event is characterized by low ?18O values from 18.0 to 14.7 ky BP, indicative of predominantly wet conditions; but a peak, never reported before, of high \'\'delta\' POT.18\'O values is recorded at 16.2 ky BP. This result is of particular importance given that the ITCZ was probably displaced even more to the south than 5ºS. In addition, the structure of the Bølling-Allerød (B/A) and Younger Dryas (YD) periods resembles that of the Greenland ice cores. Insolation control on climate at Shatuca site is evident during the Holocene, which is consistent with other Andean isotope records from different altitudes in the Peruvian Andes. The early Holocene is marked by a extremely weak SASM activity over Shatuca area, that is followed by a gradual increasing trend toward wetter conditions at the late Holocene period, this long term climate trend occurred in union with increasing insolation trend modulated by the precession cycle. Particularly wet conditions were felt in Shatuca site after 5.0 ky BP. During the Holocene, several abrupt multidecadal to centennial events are for the first time described in Andes. During the early Holocene, the most extreme event is the one logged at 9.5 ky BP, however other wet events occurred, such as the one logged at 8.1 ky BP. On the other side, during the mid Holocene, the comparison with other Andean records affected by the SASM, points out to a striking series of events that occurred between 5.1 and 5.0 ky BP. Finally, one important result from the present study is the similarity observed during the late Holocene between Shatuca cave and the Pallcacocha lake record in southern Equadorian Andes, a record that has been widely used as a proxy for El Niño Southern Oscillation (ENSO) frequency during Holocene. Shatuca record presents no clear evidence for climate control by ENSO. On the contrary, it is proposed that the increase in moisture logged between 3.5 and 2.5 ky BP, in both Pallcacocha lake and Shatuca cave records, resulted from high austral insolation control over the SASM and a major reorganization of the climatic system in the western border of the SASM at mid- to high altitudes of the Andes.

O objetivo da presente tese é o de documentar, em escala milenar, as variações paleoclimáticas e paleoceanográficas superficiais do Atlântico Sul Ocidental desde o Último Máximo Glacial. Com esta finalidade, foram obtidas estimativas de paleotemperatura, paleossalinidade e paleoprodutividade baseadas na análise de fauna de foraminíferos planctônicos, isótopos estáveis de oxigênio e carbono em Globigerinoides ruber e nove datações de radiocarbono em amostras de um testemunho coletado na Bacia de Santos. Os dados foram complementados com a reanálise de outro testemunho previamente coletado em outro setor da mesma Bacia. Os resultados demonstram que as mudanças paleoceanográficas registradas no período analisado podem ser parcialmente explicadas por variações na exportação de calor e sal para o hemisfério norte relacionadas à atividade da célula de transporte meridional e à configuração das correntes superficiais associadas à circulação atmosférica. Outra parte significativa da variabilidade parece estar relacionada à intensidade do Sistema de Monção da América do Sul resultante de variações na insolação de acordo com o ciclo de precessão. Os principais desvios da tendência de variação da composição isotópica da água do mar esperada em função das mudanças de insolação coincidem com os grandes pulsos de degelo ocorridos em torno de 19, 14 e 8,2 mil anos AP. / The goal of this thesis is to document the paleoclimatic and paleoceanographic changes occurred at the millennial scale since the Last Glacial Maximum at the surface Western South Atlantic. Paleotemperature, paleosalinity and paleoproductivity estimates were obtained for this purpose based on faunal changes of foraminifera assemblages, carbon and oxygen stable isotopes in Globigerinoides ruber and nine radiocarbon datings in a core retrieved at Santos Basin. These data were supplemented by the reanalysis of a second core previously analyzed from a different sector of the same basin. The results demonstrate that paleoceanographic changes recorded in the analyzed period may be partially explained by changes in the heat and salt export to the northern hemisphere related to the meridional overturning cell and the surface currents related to atmospheric circulation. Another significant portion of the observed variability seems to be related to changes in the strength of the South American Monsoon System resulting from insolation changes according to the precessional cycle. The main departures from the expected trend of variation in the isotopic composition of seawater related to insolation changes coincide with great meltwater pulses occurred around 19, 14, and 8.2 kyr BP.

Com base em um estudo interdisciplinar, os objetivos deste trabalho foram: estudar a dinâmica da vegetação e do nível relativo marinho e inferir o clima, durante o Holoceno, na região nordeste do estado do Espírito Santo. Para tanto foram analisados: (i) vegetação atual (caracterização botânica e \'delta\'13C e \'delta\'15N); (ii) matéria-orgânica do solo (\'delta\'13C, C elementar e datação 14C); (iii) sedimento lacustre (litologia, C e N elementar, \'delta\'13C e \'delta\'15N, datação 14C da matéria-orgânica, pólen e diatomáceas). Os pontos de amostragem estão localizados na Reserva Natural Vale e na Reserva Biológica de Sooretama, região de predomínio de Floresta Ombrófila Densa das Terras Baixas, com fragmentos de Savana e áreas ocupadas por vegetação pioneira. As principais conclusões foram: (i) o local de estudo não apresentou retração florestal durante o Holoceno; (ii) o clima foi inferido como predominantemente úmido; (iii) a dinâmica da vegetação durante o Holoceno no interior e nas proximidades do vale do Rio Barra Seca foi influenciada pelas flutuações do nível relativo marinho: com a transgressão marinha (há aproximadamente 7700 anos cal. A.P.) iniciou-se o deslocamento da vegetação florestal e a instalação do manguezal; entre aproximadamente 4700 até 3000 anos cal. A.P., o período de maior influência marinha, ocorreu o maior distanciamento do manguezal em relação ao ponto estudado; com a regressão marinha, a colonização do vale por vegetação pioneira ocorreu a partir de, aproximadamente, 2300 anos cal. A.P.; há cerca de 1200 anos cal. A.P. ocorreu a instalação do atual ambiente lacustre com a floresta em seu entorno; (iv) o local atualmente ocupado pela Lagoa do Macuco, no interior do vale do Rio Barra Seca, foi caracterizado por um ambiente estuarino durante o período aproximado de 7700 a 3000 anos cal. A.P / Based on an interdisciplinary study, the objectives of the present work were to study the vegetation and relative sea-level dynamics and to infer the climate during the Holocene, at northeastern region of Espírito Santo State. The materials and respective analyses were: (i) modern vegetation (botanic identification, \'delta\'13C and \'delta\'15N); (ii) soil organic matter (total organic carbon, \'delta\'13C and 14C dating); (iii) lake sediment (lithology, total organic carbon and total nitrogen, \'delta\'13C and \'delta\'15N, 14C dating, pollen and diatoms). The sampling points were located at Vale Natural Reserve and Sooretama Biologic Reserve, region of tropical rainforest vegetation dominance, with savanna fragments and pioneer vegetation patches. The main conclusions were: (i) the forest retreatment was not observed in the study site during the Holocene (ii) the climate was predominantly humid (iii) vegetation dynamics inside the Barra Seca River valley and surroundings were influenced by relative sea-level fluctuations: at ca. 7700 cal. yr B.P., the forest vegetation started its retreatment and the mangrove ecosystem was installed; from ca. 4700 to ca. 3000 cal. yr B.P., the period of higher marine influence, occurred the higher mangrove detachment from the sampling point; with the marine regression, the valley colonization by the pioneer vegetation started at ca. 2300 cal. yr B.P.; at ca. 1200 cal. yr B.P. started the installation of modern lacustrine environment, with the Forest in the surroundings; (iv) the present location of Lagoa do Macuco was characterized by na estuarine environment during the period from ~7700 to ca. 3000 cal. yr B.P

Dans ce travail de thèse, certaines étendues d’eaux continentales regroupant plusieurs types de système de dépôt comme les lacs, mers intérieures et lagunes ont été regroupées au sein d'un nouveau groupe de système sédimentaire mentionnés sous l'appellation de Wind-driven Water Body (WWB).Afin de caractériser l'évolution et l'enregistrement sédimentaire d'un exemple de WWB, une étude sédimentologique intégrée du bassin quaternaire du Lac Saint-Jean (Québec, Canada) a été menée à partir d'une approche intégrant géologie de terrain et imagerie géophysique très haute résolution (CHIRP 2D). A l'échelle du cortège sédimentaire, le régime glaciaire à paraglaciaire de la sédimentation et le rebond glacio-isostatique ont contrôlé au premier ordre, à la fois la succession lithologique et les architectures grandes échelles du bassin pour générer un Cortège de Régression Forcée (CRF) atypique. Au sein de ce cortège de régression forcée fini-glaciaire, une dynamique de système WWB s'est progressivement affirmée à partir de 8,5 cal. ka BP. Elle s'est exprimée par la mise en place d'une dynamique littorale importante occasionnellement associée à une circulation interne générant des courants de fonds lors d'épisodes de vents forts.Finalement, l'analyse sédimentologique du bassin du Lac Saint-Jean a permis de dégager plusieurs interprétations ayant attrait (1) à l'évolution des systèmes WWB et (2) aux séquences de déglaciation en domaine précédemment englacé. De plus, ce travail représente une contribution à l'échelle régionale pour les modalités de la dernière déglaciation du Sud-Est du Québec. / In this study, a certain number of continental enclosed basins including several depositional systems such as lakes, inland seas or lagoons have been grouped in a new sort of sedimentary system referred to as Wind driven Water Body. To characterize the sedimentary evolution and record of a WWB basin, an integrated sedimentological study has been carried out on the quaternary Saint-Jean basin (Québec, Canada) based on field onshore geology and offshore geophysics (CHIRP 2D).At the system-tract scale, the glacial to paraglacial sedimentation and the glacio-isostatic rebound controlled at first-order the lithofacies succession and large-scale architectures to generate an original Falling Stage System Tract (FSST). Within this FSST, since 8.5 cal. ka BP a WWB related sedimentary evolution overprinted the glacial to paraglacial evolution. This expressed in the form of the emplacement of an important coastal dynamics, occasionally accompanied by a lake-scale hydrodynamics at the origins of bottom currents during strong wind to storm events.Finally, the sedimentological analysis of the Saint-Jean basin brought numerous interpretations related to (1) the sedimentary evolution of WWB systems and (2) deglaciation sequences in previously glaciated domains. In addition, this work supplements the regional quaternary framework concerning the latest deglaciation evolution in southeast Quebec.