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Esta dissertação discute o contexto regional de ocupação das populações sambaquieiras do litoral sul do Estado de Santa Catarina em uma área lagunar de formação holocênica que, quando do máximo transgressivo do nível médio marinho, teria tomado a conformação de uma grande baía, com recortes microambientais variados e diversas formações insulares, denominada aqui como Paleolaguna de Santa Marta. Por meio de pesquisas bibliográficas, visitas de campo, levantamentos regionais extensivos, prospecções intensivas e intervenções arqueológicas, foi confeccionado um cadastro contendo informações de todos os sítios conhecidos na área (mais de 90 sambaquis, além de sítios relacionados aos grupos Guarani e Je do Sul), incluindo localização, implantação, estrutura estratigráfica, composição e estado de preservação, tendo-se também datado vários deles. Estes dados propiciaram uma análise de distribuição espacial e cronológica deste conjunto de sambaquis a partir de um enfoque regional, possibilitando inferências acerca do sistema de ocupação e territorialidade das populações pescadoras-caçadoras-coletoras que ali habitaram em um período compreendido entre 7000 e 1000 anos AP. / This dissertation discusses the settlement system of the sambaqui mounbuilders from the southern shores of Santa Catarina between 7000 and 1000 years BP, focusing in a regional level. The lagoonal study area has formerly been an open bay environment by the time of the transgressive maximum sea level, with a wider variety of micro-environmental settings and internal islands. By means of intensive field survey and systematic site intervening, a catalog of sites has been compiled with information on more than 90 sambaquis therein recorded so far (plus a number of later Guarani and southern Je sites), that includes site location and environmental setting, stratigraphy and composition, as well as their preservation conditions. A chronological framework has been established by dating several of these mounds, allowing the modeling of settlement evolution and territorial patterns of this long lasting, transitional, fisher-gatherer society.

A presente Dissertação estuda a ocupação pré-histórica do sítio Limeira, UTM 24K 341411 - 7714533 (40º31\'20,62\" O e 20º39\'42,61\" S); sítio arqueológico a céu-aberto localizado no município de Guarapari, região do litoral centro-sul do Estado do Espírito Santo. A pesquisa arqueológica foi pautada nos pressupostos teórico-metodológicos da Arqueologia da Paisagem, cadeia operatória e Habitus, evidenciando vestígios materiais líticos e malacológicos de uma população coletora-caçadora-pescadora que se estabeleceu no local há cerca de 670 anos AP (14C - CENA-USP). O foco da análise centrou-se na investigação da interação entre a população que habitou o sítio com o ambiente que a circundava, com levantamentos geológicos, geomorfológicos, hidrográficos, climáticos, etc., através de pesquisas bibliográficas e cartográficas. Também, buscou-se reunir informações sobre o paleoambiente do litoral do Espírito Santo, com fulcro na região estudada. A pesquisa intensiva de campo foi realizada em 4 campanhas: uma em 2009, pelo Prof. Ms. Celso Perota, via resgate arqueológico, e as demais, de cunho acadêmico, realizadas entre os anos 2012 e 2013, voltadas para esta dissertação de Mestrado, pautadas nos métodos e técnicas de investigação de campo por superfícies amplas em decapagens por camadas naturais. Como resultado, foi possível observar que o sítio Limeira é unicomponencial, além de serem evidenciadas duas estruturas estabelecidas na forma de 3 bolsões malacológicos e uma fogueira, cujos carvões foram utilizados para realização de datação. Os dados analisados possibilitaram interpretações a respeito do modo de vida dos habitantes pretéritos do sítio Limeira, e dos aspectos ambientais (vegetação e clima) que os cercava. É importante destacar que o estudo dos vestígios arqueológicos do sítio em questão e sua inserção nas escalas espaciais, temporais e ambientais, estabeleceram parâmetros de suma relevância para que futuras pesquisas desenvolvidas no Espírito Santo encontrem referenciais de suporte. / This thesis studies the prehistoric occupation of Limeira, (UTM 24K 341411-7714533 - 40º31\'20,62 \"O 20º39\'42,61 and\" S); an open-air archaeological site located in the city of Guarapari, on the south-central coast of the state of Espírito Santo, Brazil. The research was based on theoretical and methodological assumptions of Landscape Archaeology and operational chains and Habitus, showing evidence of lithic and malacological remains of a hunter-gatherer-fisher population that settled in the area around 670 years ago (14C - CENA USP). The analysis is focused on investigation into the interaction between the population that inhabited the site and the surrounding environment, encompassing geologic, geomorphologic, hydrographic and climatic surveys as well as bibliographic and cartographic research. The study also sought to gather information on the coastal paleoenvironment of Espírito Santo, with the research area serving as the fulcrum. Intensive field work was carried out in four campaigns: one in 2009, by Prof. Msc. Celso Perota via archaeological rescue, and three others of academic nature, directly related to this thesis, performed between 2012 and 2013. All field research was guided by methods and techniques for large surfaces with stripping by natural levels. As a result, it was observed that the Limeira site is uni-componential. Also highlighted were two established structures in the form of 3 malacological pockets and a fire pit, whose coals were used to perform carbon dating. Once analyzed, the data allowed for interpretations regarding the way of life of past inhabitants of the Limeira site, and the environment (vegetation and climate) around them. It is important to note that the study of the archaeological remains of the site in question - as well as their insertion into spatial, temporal and environmental scales - has established relevant parameters so that future research in Espírito Santo can be developed and supported within a greater frame of reference.

Le sujet de ma thèse traite les changements paléoenvironnementaux et paléoclimatiques qui ont affecté les écosystèmes du Moyen Atlas marocain depuis la dernière période glaciaire, centrée autour de 25,000 cal BP. Les trois séquences sédimentaires étudiées dans cette thèse ont été prélevées le long d'un transect Nord-Sud dans le Moyen Atlas. Cette étude est basée sur une approche multi-bioindicateurs intégrant la palynologie, la géochimie élémentaire et la granulométrie afin de comprendre la dynamique des écosystèmes passés et de mettre en évidence les impacts anthropiques sur ces écosystèmes et leurs bassins versants. Les résultats obtenus montrent que durant la dernière période glaciaire et jusqu’au début de l’holocène, une végétation steppique a dominé les paysages du Moyen Atlas en réponse à des conditions climatiques froides et arides. Cependant, des populations de cèdres, de chênes et de pins ont persisté durant la période glaciaire dans des micro-refuges. Bien que le début de l’holocène révèle une expansion des chênes et des pins (principaux composants des écosystèmes forestiers méditerranéens), la steppe (composée d'armoise, de chénopodiacées et de graminées) a persisté jusqu’à 6.5 ka cal BP. Ces écosystèmes tolérant à la sécheresse reflètent un début de l’holocène chaud mais avec une quantité de précipitations annuelles assez réduite pour permettre l'expansion des forêts tel que nous l'observons en Europe et d’autres régions de la Méditerranée. Ce n'est qu'à partir de 6.5 ka cal BP que les forêts de cèdre s’installent aux altitudes des sites étudiés (autour de 1600m) et que des plantes aquatiques prolifèrent dans les marais ou nous avons effectué les sondages. Nous observons ensuite une nette régression du couvert arboré à partir de 4.5 ka cal BP, notamment les chênes décidus, et une expansion des taxons herbacés. Ceci est le résultat d’une tendance vers des conditions plus arides témoignant d'une installation du climat méditerranéen tel que nous le connaissons aujourd'hui. Le début des changements environnementaux liés à l'impact humain, à travers les données palynologiques et géochimiques, n'est enregistré qu’à partir de ca. 1500 cal BP. Les résultats obtenus dans cette thèse sont en accord avec ceux d'autres études paléoenvironnementales menées en Méditerranée autant pour la période glaciaire que pour le début des conditions arides à partir de 5.5 ka cal BP. / This thesis discusses the paleoenvironmental and paleoclimatic changes that have affected the ecosystems of the Moroccan Middle Atlas since the last glacial period, and focuses around 25000 cal BP. The three sedimentary sequences that have been studied in this thesis were taken along a North-South transect in the Middle Atlas. This study is based on a multi-bio-indicators approach, including palynology, geochemical elements and particle size, in order to better understand the dynamic of previous ecosystems and to highlight the human activities on these ecosystems and on their catchment areas.The results obtained show that during the last glacial period, and until the beginning of the Holocene, steppe vegetation was predominant in the Middle Atlas, in reaction to cold and arid climate conditions. However, populations of cedars, oaks and pine trees remained in micro-refugia. Although the beginning of the Holocene reveals an expansion of oaks and pines trees (the main components of Mediterranean forests ecosystems), the steppe (which is composed of Artemisia, Chenopodiaceae and grasses) persisted till 6.5 ka cal BP. These drought-tolerant ecosystems reflect a warm beginning of the Holocene, with an amount of precipitation that was low enough to allow the expansion of forests similar to those we can observe in Europe and other areas of the Mediterranean. It’s only since 6.5 ka cal BP that cedars forests have started to grow at the altitudes of the sites we studied (around 1600m), and that aquatic plants have proliferated in the marshes where we took our samples. We can then observe a sharp decline of tree cover, including deciduous oaks, starting 4.5 ka cal BP and an expansion of herbaceous taxa. These are the consequences of a tendency to conditions that were more arid, attesting the installation of the Mediterranean climate as we know it today. The first environmental changes linked to human impact have only been recorded, through palynology and biochemical data, from ca. 1500 cal BP. The results obtained in this thesis are in line with those obtained in other paleoenvironmental studies conducted in the Mediterranean area, for the glacial period as well as for the beginning of arid conditions starting 5.5 ka cal BP.

Cette thèse est une étude du bassin d’avant-pays de l’Oural méridional au Kazakhstan (Mougodjar) à partir de données sédimentologiques (affleurements) et de sub-surface (profils sismiques, puits). Une étude sédimentologique des séries turbiditiques d’âge Carbonifère terminal-Permien inférieur a été menée dans le Mougodjar. L’étude des dépôts a permis de caractériser les environnements des dépôts turbiditiques et de mettre en évidence des séquences de long terme se succédant du Carbonifère terminal au Permien inférieur. L’analyse des faciès turbiditiques montre que les séquences de long terme sont contrôlées par les fluctuations du niveau marin global sous contrôle glacio-eustatique. L’orogenèse du Permien inférieur associée à la surrection de l’Oural a contrôlé le volume et la nature des apports sédimentaires alimentant le bassin d’avant-pays. Ceci se traduit par l’importance variable des conglomérats et brèches de démantèlement du matériel volcanique et des plate-formes carbonatées situées sur les marges du bassin et par des réorganisations locales des pentes sous-marines (changements de sens des paléo-courants). Les minéraux smectitiques dominent les assemblages argileux analysés dans les séries du Carbonifère terminal au Permien inférieur. L’illite, la kaolinite et la chlorite sont présentes en plus faibles proportions. Les assemblages argileux indiquent une relative pérennité des apports détritiques qui varient au cours du temps selon la distribution des faciès turbiditiques. Les fluctuations climatiques n’apparaissent pas contrôler la distribution des minéraux argileux qui semble plutôt associée (1) à l’érosion de stocks argileux variés en fonction des fluctuations eustatiques et/ou (2) à la redistribution du matériel détritique le long d’un transect proximal-distal sous l’effet de processus de tri granulométrique. La distribution de la matière organique principalement marine du Dévonien moyen au Carbonifère, montre que les paléoenvironnements étaient favorables à de fortes paléo-productivité de surface probablement associées à une dysoxie/anoxie de toute ou partie de la colonne d’eau, dans un contexte de bassin marin restreint. Les plus fortes valeurs de COT (20 %) mesurées dans la coupe de Kiya (Famennien) sont pourraient être associées à un des OAEs majeurs du Dévonien, l’évènement Hangenberg, mais la précision des données biostratigraphiques disponibles ne permet pas de l’assurer. Quoi qu’il en soit, les OAE qui se succèdent au Dévonien auraient pu favoriser l’accumulation et la préservation de la matière organique dans le Dévonien du Mougodjar, en plus des facteurs physiographiques (restriction du bassin vers le sud). Les fortes concentrations en carbone organique (COT 20%) des sédiments dévoniens montrent de bonnes roches mères potentielles. Les teneurs en carbone organique, surtout d’origine terrestre, des sédiments turbiditiques permiens sont plus faibles (COT pouvant cependant atteindre 4%) mais assez élevées dans certains niveaux stratigraphiques. Les faciès silto-sableux proximaux ont livré les plus fortes concentrations en COT. Ces turbidites permiennes ont des caractéristiques de réservoirs. Elles peuvent aussi se révéler de roches-mères gas-prone potentielles. L’interprétation des données de sub-surface nous a permis de préciser la structure du bassin d’avant-pays à l’échelle de l’Oural méridional. Il est constitué de plis et de chevauchements à vergence est qui résultent d’une évolution polyphasée. Les plis s’amortissent vers l’ouest et passent à la partie peu déformée du bassin puis à la plate-forme. A partir de ces données nous avons reconstruit des schémas d’évolution tectono-sédimentaire et des cartes paléogéographiques de la partie occidentale du Mougodjar. / This thesis is dedicated to the study of the foreland basin of southern Ural in Kazakhstan (Mougodjar). Sedimentological data have been collected from field investigations, and sub-surface data (seismic profiles, wells) have been studied. A sedimentological investigation of the turbidites, Carboniferous to Early Permian in age, has been performed. It allowed to characterize the environments of deposition of the turbidites and to evidence the long-term succession from uppermost Carboniferous to early Permian. The analysis of turbides indicates that the long-term sequences are controlled by global sea-level changes controlled by glacio-eustatism. The Early Permian orogeny, associated to the uplift of the Ural chain, controlled the quantity and quality of the sedimentary input sourcing the foreland basin. Important variations in the conglomeratic levels reflect (1) the erosion of material from the volcanic arc and carbonate platforms constituting the margins of the basin, and (2) local reorganizations of sub-marine slopes (changes in paleo-current directions). The smectitic minerals are the most frequent in the clay minerals assemblages reported in the uppermost Carboniferous to Early Permian sequences. Illite, Kaolinite, and chlorite are less frequently observed. This assemblage of clay minerals shows a permanence of detrital sources filling the basin. This pattern is thought to reflect a sorting effect of the clay particles along a proximal-distal transect, either than a direct paleoclimatic control. The distribution of the organic matter, mainly marine from the Middle Devonian to the Carboniferous indicates that the paleoenvironments were looked favourable to high surface paleoproductivities associated to a dysoxy/anoxy of all, or part, of the water column in the context of a restricted marine basin. The highest values of COT (20 %) found in the Kiya section (Fammenian) may be associated to a major Devonian OAE, the Hangenberg event. However, the accuracy of available biostratigraphic data does not allow to ensure such correlation. Indeed, OAE events may have favoured the accumulation and preservation of the organic matter in the Mougodjar, in addition to physiographical effects (e.g., the relative closure of the basin toward the south). The high concentration in organic carbon (COT 20%) of the Devonian sediments shows good potential source rocks. The content in organic matter, mainly from terrestrial origin, of the Permian turbidites are lower (COT reaching up to 4%), but quite high in some stratigraphic levels. The proximal silty-sandy deposits display the higher COT values. These Permian turbidites may be good reservoirs. They could also be potential gas-prone source rocks. The study of the sub-surface data allowed us to determine the structure of the foreland basin at the scale of southern Ural. It is constituted of folds and west-vergent thrusts resulting from a polyphased tectonic evolution. The folds gradually disappear toward the west passing westward either to the stable Russian platform in the north or to the eastern Pre-Caspian basin to the south. We have reconstructed the tectono-sedimentary evolution of the western Mougodjar through paleogeographic maps. Five key periods have been selected between the Devonian to early Permian period. Our reconstructions evidence two main orogenic events: (1) a first collision between the European continent and the Magnitogorsk volcanic arc in Middle Devonian, and (2) the major uralian orogeny during the Late Carboniferous to Early Permian times resulting from the collision of the European continent with the Kazakh and Siberian plates. This event originated the foreland basin, which is almost completely fulfilled by a thick detrital sequence. In Kungurian, the foreland basin is almost completely isolated and a thick evaporitic sequence deposited.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-11-14T19:00:02Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Deyvis Willian.pdf: 3401576 bytes, checksum: a6d75e7142dc9d25810cea59f381554b (MD5) / Made available in DSpace on 2018-11-14T19:00:02Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Deyvis Willian.pdf: 3401576 bytes, checksum: a6d75e7142dc9d25810cea59f381554b (MD5) Previous issue date: 2018-09-14 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Este trabalho apresenta um estudo em escala de detalhe regional para a compreensão das configurações paleoambientais do Quaternário em três regiões planálticas do estado do Paraná, sul do Brasil (Ponta Grossa, Guarapuava e Palmas). Para tanto utilizou-se como principal objeto de análise assembleias fitolíticas, aliados a dados isotópicos da matéria orgânica do solo e datações 14C, extraídos de testemunhos de Organossolo em altitudes que variaram de 850 a 1.280 metros. Para o reverso da Escarpa Devoniana, em Ponta Grossa, os resultados sugerem que desde 34.550 anos cal. AP até 11.000 anos cal. AP vigorou na região um clima mais frio e seco que o atual, dominado por vegetação campestre. Diferentemente, na Serra da Esperança, em Guarapuava, no período entre 13.660 e 10.000 anos AP, apesar do clima mais frio que o atual, havia umidade suficiente para que vegetação do tipo florestal predominasse. Para ambos os locais, no entanto, o intervalo entre 10-11.000 e 5-6.000 anos AP é marcado por um ambiente de maior aridez, ocupado por um mosaico floresta/campo com prevalência campestre. A partir de 6.000 anos AP inicia-se uma mudança significativa no sentido de um clima mais quente e úmido. Mas, enquanto na Escarpa Devoniana a vegetação assume configuração semelhante a atual, propícia a formação de um mosaico campo/floresta, na Serra da Esperança a vegetação tende a ser bem mais fechada, num mosaico floresta/campo. O testemunho de Palmas abrange apenas os últimos 4.920 anos cal. AP e sugere o estabelecimento de um ambiente característico de mosaico campo/floresta, gradativamente mais aberto. A partir dos últimos 1.500 anos AP, mudanças na configuração de gramíneas sugerem um ambiente mais úmido, sob condições climáticas mais próximas às atuais, uma típica paisagem de campo entremeada por agrupamentos florestais. Os dados apontam possíveis variações na intensidade de mudanças climáticas no Pleistoceno Tardio em função de diferenças no relevo planáltico e sua capacidade de interferência microclimática. / This paper presents a study on a detailed regional scale for understanding the Quaternary paleoenvironmental settings in the Paraná Highlands, Southern Brazil (Ponta Grossa, Guarapuava, and Palmas. The main object of analysis was phytolitc assemblies, combined with isotopic data of soil organic matter and carbon-14 dating, sampled from peat testimonies at altitudes that ranged from 850 to 1,280 m. For the reverse of the Escarpa Devoniana, in Ponta Grossa, the results suggest that since 34,550 yrs. cal BP up to 11,000 yrs. cal BP the region had a colder and dryer climate than the current one, dominated by grassland. In contrast, in Serra da Esperança, in Guarapuava, in the period between 13,660 yrs. cal BP up to 10,000 yrs. cal BP despite the colder climate than the current, there was enough moisture for a kind of forest predominance. For both locations, however, the interval between 10-and 56,000 yrs. 11,000 BP is marked by greater aridity, occupied by a mosaic forest/field with prevalence of grasses. From 6,000 yrs. BP, it begins a significant shift towards a warmer moister climate. Nevertheless, while in the Escarpa Devoniana vegetation takes similar configuration to the current one, favorable to a mosaic field/forest, in Serra da Esperança the vegetation tends to be much more closed, as a mosaic forest/field. The Palmas testimony only comprises the last years 4,920 yrs. cal BP and suggests the establishment of an environment of mosaic field/forest, gradually more open. From the past 1,500 yrs., changes in grassland configuration suggest a moister environment under climatic conditions closer to the present, a typical grassland landscape with forest patches. The data indicate possible variations in the intensity of climate change in the Late Pleistocene due to differences in the Highlands’ relief and its capacity of microclimatic interference.

A presente Dissertação estuda a ocupação pré-histórica do sítio Limeira, UTM 24K 341411 - 7714533 (40º31\'20,62\" O e 20º39\'42,61\" S); sítio arqueológico a céu-aberto localizado no município de Guarapari, região do litoral centro-sul do Estado do Espírito Santo. A pesquisa arqueológica foi pautada nos pressupostos teórico-metodológicos da Arqueologia da Paisagem, cadeia operatória e Habitus, evidenciando vestígios materiais líticos e malacológicos de uma população coletora-caçadora-pescadora que se estabeleceu no local há cerca de 670 anos AP (14C - CENA-USP). O foco da análise centrou-se na investigação da interação entre a população que habitou o sítio com o ambiente que a circundava, com levantamentos geológicos, geomorfológicos, hidrográficos, climáticos, etc., através de pesquisas bibliográficas e cartográficas. Também, buscou-se reunir informações sobre o paleoambiente do litoral do Espírito Santo, com fulcro na região estudada. A pesquisa intensiva de campo foi realizada em 4 campanhas: uma em 2009, pelo Prof. Ms. Celso Perota, via resgate arqueológico, e as demais, de cunho acadêmico, realizadas entre os anos 2012 e 2013, voltadas para esta dissertação de Mestrado, pautadas nos métodos e técnicas de investigação de campo por superfícies amplas em decapagens por camadas naturais. Como resultado, foi possível observar que o sítio Limeira é unicomponencial, além de serem evidenciadas duas estruturas estabelecidas na forma de 3 bolsões malacológicos e uma fogueira, cujos carvões foram utilizados para realização de datação. Os dados analisados possibilitaram interpretações a respeito do modo de vida dos habitantes pretéritos do sítio Limeira, e dos aspectos ambientais (vegetação e clima) que os cercava. É importante destacar que o estudo dos vestígios arqueológicos do sítio em questão e sua inserção nas escalas espaciais, temporais e ambientais, estabeleceram parâmetros de suma relevância para que futuras pesquisas desenvolvidas no Espírito Santo encontrem referenciais de suporte. / This thesis studies the prehistoric occupation of Limeira, (UTM 24K 341411-7714533 - 40º31\'20,62 \"O 20º39\'42,61 and\" S); an open-air archaeological site located in the city of Guarapari, on the south-central coast of the state of Espírito Santo, Brazil. The research was based on theoretical and methodological assumptions of Landscape Archaeology and operational chains and Habitus, showing evidence of lithic and malacological remains of a hunter-gatherer-fisher population that settled in the area around 670 years ago (14C - CENA USP). The analysis is focused on investigation into the interaction between the population that inhabited the site and the surrounding environment, encompassing geologic, geomorphologic, hydrographic and climatic surveys as well as bibliographic and cartographic research. The study also sought to gather information on the coastal paleoenvironment of Espírito Santo, with the research area serving as the fulcrum. Intensive field work was carried out in four campaigns: one in 2009, by Prof. Msc. Celso Perota via archaeological rescue, and three others of academic nature, directly related to this thesis, performed between 2012 and 2013. All field research was guided by methods and techniques for large surfaces with stripping by natural levels. As a result, it was observed that the Limeira site is uni-componential. Also highlighted were two established structures in the form of 3 malacological pockets and a fire pit, whose coals were used to perform carbon dating. Once analyzed, the data allowed for interpretations regarding the way of life of past inhabitants of the Limeira site, and the environment (vegetation and climate) around them. It is important to note that the study of the archaeological remains of the site in question - as well as their insertion into spatial, temporal and environmental scales - has established relevant parameters so that future research in Espírito Santo can be developed and supported within a greater frame of reference.

Ce mémoire présente l'étude du signal phytolithique de sédiments mio-pliocènes du Tchad(Afrique Centrale) datés entre 7-2 Ma, et contemporains des Homininés anciens Sahelanthropustchadensis et Australopithecus bahrelghazali. Une calibration de la relation plantes-phytolithes-solspour l'Afrique tropicale subsaharienne actuelle a d'abord été réalisée pour apprécier la signatureenvironnementale des phytolithes dans le registre fossile. L'analyse des assemblages phytolithiques de98 espèces de graminées (Poaceae) a permis d'élaborer trois nouveaux indices phytolithiques à partirde 43 types propres aux Poaceae. Testés sur une base de 57 sols/sédiments modernes du Tchad, cesindices permettent de tracer les associations graminéennes aquatiques du Lac Tchad, les associationsmésophytiques des milieux humides soudaniens, et les associations xérophytiques des milieux secssahéliens. L'analyse des assemblages phytolithiques des sols/sédiments actuels considérés dans leurensemble a permis d'évaluer le potentiel de ce proxy à caractériser la physionomie des formationssoudano-sahéliennes modernes. La calibration a été appliquée à l'étude d'un enregistrementsédimentaire discontinu du Lac Tchad (6-2 Ma) (forage de Bol, 13°N/14°E) et à celle de 18 niveauxpaléontologiques du Djourab (7-3.5 Ma) (16°N/17°E). Les résultats indiquent la présence de savanesintermédiaires à fermées et de zones de végétation aquatique dominantes à 7 Ma dans le Djourab, puisde savanes plus ouvertes et sèches à 3.5 Ma. Une phase de bas niveau lacustre est enregistrée entre3.6-2.8 Ma à Bol, et un pic d'aridité à 3.2 Ma. Enfin, les résultats montrent l'existence de graminéesen C4 au Tchad depuis 7 Ma. / This thesis dissertation is dedicated to the study of the phytolith signal of Mio-Pliocenesediments from Chad (Central Africa) dated between 7-2 Ma, and contemporary to the early Homininspecies Sahelanthropus tchadensis and Australopithecus bahrelghazali. A calibration work studyingthe relationship plants-phytoliths-soils in modern sub-Saharan tropical Africa was carried out in orderto assess the environmental significance of the phytolith signal in the fossil record. Phytolithassemblages produced by 98 sub-Saharan grass species (Poaceae) were analyzed and the results led tothe development of three new phytolith indices defined from 43 types specific to Poaceae. Tested on adatabase of 57 modern soil/sediment samples from Chad, these indices allow drawing aquatic grassassociations of Lake Chad, mesophytic grass associations of wetlands from the Sudanian domain, andxerophytic grass associations of drylands from the Sahelian domain. The analysis of modern soilphytolith assemblages (total assemblages) was used to assess the potential of this proxy to characterizethe physiognomy of the Sudano-Sahelian vegetation types. The calibration had been applied to thestudy of a discontinuous sedimentary record from Lake Chad (6-2 Ma) (Bol core, 13°N/14°E) and of18 paleontological levels from the Djourab (7-3.5 Ma) (16°N/17°E). The results indicate thedominance of intermediate to closed savannas and areas of aquatic vegetation at 7 Ma in the Djourab,and more open and dry savannas at 3.5 Ma. A limited lacustrine stage is recorded between 3.6-2.8 Maat Bol, and a shift of aridity at 3.2 Ma. Finally, the results show the existence of C4 grasses in Chadsince 7 Ma.

Computational evolutionary analyses, particularly phylogenetics and ancestral reconstruction, have been extensively exploited under different algorithms and evolutionary models to better understand genome evolution from both small- and large-scale perspectives in order to assign genotypes based on assortment, resolve species relationships and gene annotation issues, further understand gene gain/loss within individual gene families, measure functional divergence among homologs, and infer ancestral character states. These evolutionary studies provide us with insights into biologically relevant issues including paleoenvironments inferred from resurrected proteins, developmental physiology associated with functional divergence of duplicated genes, viral epidemics and modes of transmission in attempt to better prepare, prevent and control diseases, evolution of lineage-specific pathogenicity, and attempts to create a synthetic ancient organism that would benefit the field of synthetic biology. Our work also provides us with greater insights into the accuracies and limitations of ancestral sequence reconstruction methods. In total, our work highlights the diverse questions that evolutionary studies attempt to address and the different biological levels that can be studied to answer these questions.