The Tamengo Formation holds important and well preserved sedimentological and paleontological records of Upper Ediacaran Period. Previous works had centred on Corcal Mine, Saladeiro (now Sobramil Port) and Laginha Sections. However, there is no reports of detailed sedimentological and geochemical surveys on those and other outcrops of the Tamengo Formation at Corumbá-Ladário escarpment located at Paraguay River margins where the paleontological occurrences are concentrated. In the aim of contribute to the understanding of the paleo-environmental conditions, paleontological occurrences and its relationship at Tamengo Formation, detailed stratigraphic columns, description and interpretation of sedimentary facies, sampling, petrography, C and O isotope analysis along with other geochemical analysis were carried out on Corcal Mine, Sobramil Port and six new sections located along the Escarpment. From the obtained data, eight different facies and its C isotope signature were recognized: Wavy Bedding Mudstone (mean \'delta 13C, PDB\' =3.83%o PDB), Hummocky/Cross-Stratified Wackestone (mean \'delta 13C, PDB\' =3.98%o PDB), Cloudina Grainstone (mean \'delta 13C, PDB\' =4.36%o PDB), Intraclastic Packstone-Grainstone (mean \'delta 13C, PDB\' =4.19%o PDB), Low-Angle Cross-Laminated/Laminated Wackestone (mean \'delta 13C, PDB\'=4.93%o PDB), Cloudina Packstone (mean \'delta 13C, PDB\' =4.74%o PDB), Pelite, and Reworked Volcanic Tuff Facies, in which the Formation was dated by other authors, yielding an approximated age of 542 Ma. Also, very well-preserved C and O isotopic signatures were recognized. The carbon isotope data reveal more positive \'delta 13C, PDB\' values on coarser facies (Grainstone, Wackestone, Packstone) and in the calcareous beds overlying the Pelite facies, conforming six main distinctive patterns for carbonate facies that match with coarsening upwards cycles composing the Tamengo Formation. A ramp context of sedimentation has been interpreted for the Tamengo Formation, under strong storms influence, with a progressive tendency towards more positive \'delta 13C, PDB\' values from the deepest to shallower facies. A mid to outer ramp context was inferred for the Ladário-Corumbá, Goldfish, Sobramil and lower part of the Corcal Mine sections, with a mean \'delta 13C, PDB\' value of 3.97%o. For the mid part of the ramp two settings were interpreted; bioclastic lens represented by the Cloudina Grainstone and Intraclastic Packstone-Grainstone Facies and subcoastal setting, represented by the Low-Angle Cross-Laminated/Laminated Wackestone and Cloudina Packstone Facies with mean \'delta 13C, PDB\' values of \'delta 13C, PDB\' =4.33%o and \'delta 13C, PDB\' =4.87%o respectively, represented in the middle and upper part of the Corcal Mine Section. Also, the commonly addressed distribution of Cloudina and Corumbella on different facies could be the reflex of the oscillation between storms and fair-weather conditions; periodic influence of storm-waves or even typhoons in the ramp could avoid Cloudina fixation promoting constantly reworking and accumulating the shells on carbonate facies, while Corumbellas, probably restricted to deepest part of the ramp, expanded to the shallow parts of the ramp on fair weather conditions between storms, as settling by decantation of the Pelite Facies take place at the ramp, explaining the typic distribution of Cloudina restricted to carbonate facies and Corumbella to the interbedded Pelite Facies. / A Formação Tamengo possui importantes e bem preservados registros sedimentológicos e paleontológicos da parte superior do período Ediacarano. Trabalhos anteriores centraram-se nas secções das minas Corcal, Saladeiro (atual Porto Sobramil) e Laginha. No entanto, não há descrições de levantamentos sedimentológicos e geoquímicos detalhados sobre esses e outros afloramentos da Formação Tamengo na escarpa de Corumbá- Ladário, as margens do Rio Paraguai, onde as ocorrências paleontológicas estão concentradas. Com o objetivo de contribuir para o entendimento das condições paleoambientais, ocorrências paleontológicas e sua relação com a Formação Tamengo, perfis estratigráficos, amostragem, petrografia, análises de isótopos C e O e outras investigações geoquímicas foram realizadas na mina Corcal e Porto Sobramil e seis novas seções localizadas ao longo da referida escarpa. A partir dos dados obtidos, oito diferentes facies foram reconhecidas com suas respectivas assinaturas de isótopos de C: Wavy Bedding Mudstone (média \'delta 13C, PDB\'=3.83%o PDB), Hummocky/Cross-Stratified Wackestone (média \'delta 13C, PDB\' =3.98%o PDB), Cloudina Grainstone (média \'delta 13C, PDB\' =4.36%o PDB), Intraclastic Packstone-Grainstone (média \'delta 13C, PDB\' =4.19%o PDB), Low-Angle Cross-Laminated/Laminated Wackestone (média \'delta 13C, PDB\' =4.93%o PDB), Cloudina Packstone (média \'delta 13C, PDB\' =4.74%o PDB),Pelite e Reworked Volcanic Tuff Facies, na qual o topo da Formação Tamengo foi datada por outros autores, com idade aproximada de 542 Ma . Os valores de isótopos revelam valores de \'delta 13C, PDB\' mais positivos nas facies carbonáticas sobrepostas às Facies Pelito e nas de granulação mais grossa (Grainstone, Packstone, Wackstone), configurando seis padrões distintos para as fácies carbonáticas que coincidem, por sua vez, com os ciclos de raseamento ascendentes que compõem a Formação Tamengo. A Formação Tamengo tem sido interpretada como depositada em rampa carbonática sob ação de tempestades, onde se observa uma tendência para valores mais positivos do \'delta 13C, PDB\' das partes mais profundas para as partes rasas da rampa. Um contexto de rampa média para externa foi inferido para as seções Ladário-Corumbá, Goldfish, Sobramil e parte inferior da Mina Corcal, com um valor médio de \'delta 13C, PDB\' = 3,97 %o. Para a parte media da rampa, duas configurações foram interpretadas; lentes bioclásticos marcada pela presença das facies Cloudina Grainstone e Intraclastic Packstone-Grainstone e sublitoraneo marcada pela presença das facies Low-Angle Cross-Laminated/Laminated Wackestone e Cloudina Packstone, as duas configurações com valores médios de \'delta 13C, PDB\' = 4,33 e \'delta 13C, PDB\' = 4,87%o, respectivamente, representados na parte média e superior da Seção Mina Corcal. Além disso, a distribuição comumente observada de Cloudina e Corumbella em diferentes fácies poderia ser o reflexo da oscilação entre tempestades e condições de bom tempo; a influência periódica das ondas de tempestades ou possível tufões na rampa, teriam evitado a fixação das Cloudinas e promovido o constante retrabalhamento de suas caparaças, acumuladas nas fácies carbonáticas. Enquanto os Corumbellas provavelmente restritas às partes profundas da rampa, avançavam para as partes mais rasas durantes os intervalos das tempestades, quando se estabeleciam também, as condições de decantação de argila na rampa (Fácies Pelito), o que explicaria a típica distribuição de Cloudinas, apenas nas fácies carbonáticas, e Corumbella restritas às intercalações de pelitos.

Systeme von Vorlandbecken repräsentieren bedeutende geologische Archive und dienen dem Verständnis von Rückkopplungen zwischen oberflächennahen und tektonischen Prozessen. Außerdem dokumentieren sie die Entwicklung unmittelbar angrenzender Bergketten. Die sedimentären Abfolgen in Vorlandbecken reflektieren das Gleichgewicht zwischen tektonischer Subsidenz, der Bildung langzeitlichen Akkommodationsraumes und des Sedimenteintrages, welcher wiederum die Wirksamkeit von Erosions- und Massenneuverteilungsprozessen wiederspiegelt. Um die Effekte von Klima und Tektonik in einem solchen System zu erforschen, untersuchte ich die Oligo-Miozänen Sedimente in den Vorlandbecken der südlichen Elburs Bergkette, einem intrakontinentalen Gebirge in Nord-Iran, das im Zuge der Arabisch-Eurasischen Kontinent-Kollision herausgehoben wurde. In dieser Studie der Vorlandbeckensedimente wurden Datierungstechniken angewandt (40Ar/39Ar, (U-Th)/He Thermochronologie und Magnetostratigraphie), die Sedimente und deren Herkunft analysiert und die Tonmineralogie, sowie Sauerstoff- und Kohlenstoffisotope untersucht. Die Ergebnisse zeigen, dass auf einer Zeitskala von 105 bis 106 Jahren eine systematische Korrelation zwischen „coarsening upward“ Zyklen und den sedimentären Akkumulationsraten besteht. Während sukzessiver Überschiebungsphasen werden die durch Hebung der Bergkette bereitgestellten groben Kornfraktionen in proximale Bereiche des Beckens geliefert und feinkörnige Fazies in distalen Beckenregionen abgelagert. Variationen in der Sedimentherkunft in Phasen größerer tektonischer Aktivität zeugen von erosionaler Abdeckung und/oder der Umorganisation natürlicher Entwässerungsstrukturen. Außerdem zeigen die Untersuchungen an stabilen Isotopen, dass die verstärkte tektonische Aktivität das Anwachsen der Topographie förderte und damit die Wirksamkeit einer topographischen Barriere erhöhte. Wenn aufgrund nachlassender Beckenabsenkung die grobe Kornfraktion nicht vollständig im Nahbereich des Beckens aufgenommen werden kann breitet sie sich in ferne Beckenregionen aus. Im Elburs wird die verringerte Subsidenz durch eine interne Hebung des Vorlandes hervorgerufen und ist mit einer lateralen Stapelung von Flussbetten assoziiert. Dokumentiert wird dies anhand konsequenten Schichtwachstums, tektonischer Schrägstellung und sedimentärer Umlagerung. Gleichzeitig nehmen die Sedimentationsraten zu. Die Sauerstoff-Isotope der Paläoböden zeigen, dass dieser Anstieg mit einer Phase feuchteren Klimas einhergeht, wodurch Oberflächenprozesse effizienter werden und Heraushebungssraten steigen, was eine positive Rückkopplung erzeugt. Des Weiteren zeigen die isotopischen und sedimentären Daten, dass seit 10-9 Millionen Jahren (Ma) das Klima durch saisonalen Anstieg der Niederschläge zunehmend feuchter wurde. Da bedeutende klimatische Veränderungen zu dieser Zeit auch im Mittelmeerraum und Asien beobachtet wurden, ist anzunehmen, dass die klimatische Veränderung, die im Elburs Gebirge beobachtet wird, höchstwahrscheinlich Änderungen der atmosphärischen Zirkulationen der nördlichen Hemisphäre reflektiert. Aus den Ergebnissen dieser Studie lassen sich zusätzliche Implikationen für die Entwicklung des Elburs Gebirges und die Arabisch-Eurasische kontinentale Kollisionszone ableiten. Die orogen-weite Hauptdeformation propagierte nicht gleichmäßig nach Süden, sondern seit dem Oligozän schrittweise vorwärts und rückwärts. Insbesondere von ~17,5 bis 6,2 Ma wurde das Gebirge durch eine Kombination aus frontaler Akkretion und interner Keildeformation in Schritten von 0,7 bis 2 Millionen Jahren herausgehoben. Darüber hinaus deuten die Sedimentherkunftsdaten darauf hin, dass sich noch vor 10-9 Ma die Haupteinengungsrichtung von NW-SE nach NNE-SSW veränderte. Regional erlaubt die Geschichte der untersuchten Becken und angrenzenden Gebirgszüge Rückschlüsse auf ein neues geodynamisches Model zur Entwicklung der Arabisch-Eurasischen kontinentalen Kollisionszone. Zahlreiche Sedimentbecken des Elburs Gebirges und anderer Lokalitäten der Arabisch-Eurasischen Deformationszone belegen einen Wechsel von einem tensionalen zu einem kompressionalen tektonischen Regime vor ~36 Ma . Dieser Wechsel könnte den Beginn der Subduktion von gedehnter arabischer kontinentaler Lithosphäre unter Zentral-Iran bedeuten, was zu einer moderaten Plattenkopplung und Deformation von Unter- sowie Oberplatte geführt hat. Der Anstieg der Deformationsraten im südlichen Elburs Gebirge seit ~17,5 Ma lässt vermuten, dass die Oberplatte, wahrscheinlich aufgrund steigender Plattenkopplung, seit dem frühen Miozän signifikant deformiert wurde. Diese Veränderung könnte der Subduktion mächtigerer arabischer kontinentaler Lithosphäre zugeschrieben werden und den Anfang echter kontinentaler Kollision bedeuten. Dieses Model erklärt daher die Zeitverzögerung zwischen der Initiation der Arabisch-Eurasischen kontinentalen Kollision (Eozän-Oligozän) and dem Beginn ausgedehnter Deformation in der Kollisionszone (Miozän). / Foreland-basin systems are excellent archives to decipher the feedbacks between surface and tectonic processes in orogens. The sedimentary architecture of a foreland-basin system reflects the balance between tectonic subsidence causing long-term accommodation space and sediment influx corresponding to efficiency of erosion and mass-redistribution processes. In order to explore the effects of climatic and tectonic forcing in such a system, I investigated the Oligo-Miocene foreland-basin sediments of the southern Alborz mountains, an intracontinental orogen in northern Iran, related to the Arabia-Eurasia continental collision. This work includes absolute dating methods such as 40Ar/39Ar and zircon (U-Th)/He thermochronology, magnetostratigraphy, sedimentological analysis, sandstone and conglomerate provenance study, carbon and oxygen isotope analysis, and clay mineralogy study. Results show a systematic correlation between coarsening-upward cycles and sediment accumulation rates in the basin on 105 to 106yr time scales. During thrust loading phases, the coarse-grained fraction supplied by the uplifting range is stored in the proximal part of the basin (sedimentary facies retrogradation), while fine-grained sediments are deposited in distal sectors. Variations in sediment provenance during these phases of enhanced tectonic activity give evidence for erosional unroofing phases and/or drainage-reorganization events. In addition, enhanced tectonic activity promoted the growth of topography and associated orographic barrier effects, as demonstrated by sedimentologic indicators and the analysis of stable C and O isotopes from calcareous paleosols and lacustrine/palustrine samples. Extensive progradation of coarse-grained deposits occurs during phases of decreased subsidence, when the coarse-grained fraction supplied by the uplifting range cannot be completely stored in the proximal part of the basin. In this environment, a reduction in basin subsidence is associated with laterally stacked fluvial channel deposits, and is related to intra-foreland uplift, as documented by growth strata, tectonic tilting, and sediment reworking. Increase in sediment accumulation rate associated with progradation of vertically-stacked coarse-grained fluvial channels also occurs. Paleosol O-isotope data shows that this increase is related to wetter climatic phases, suggesting that surface processes are more efficient and exhumation rates increase, giving rise to a positive feedback. Furthermore, isotopic and sedimentologic data show that starting from 10-9 Ma, climate became less arid with an increase in seasonality of precipitation. Because important changes were also recorded in the Mediterranean Sea and Asia at that time, the evidence for climatic variability observed in the Alborz mountains most likely reflects changes in Northern Hemisphere atmospheric circulation patterns. This study has additional implications for the evolution of the Alborz mountains and the Arabia-Eurasia continental collision zone. At the orogenic scale, the locus of deformation did not move steadily southward, but stepped forward and backward since Oligocene time. In particular, from ~ 17.5 to 6.2 Ma the orogen grew by a combination of frontal accretion and wedge-internal deformation on time scales of ca. 0.7 to 2 m.y. Moreover, the provenance data suggest that prior to 10-9 Ma the shortening direction changed from NW-SE to NNE-SSW, in agreement with structural data. On the scale of the entire collision zone, the evolution of the studied basins and adjacent mountain ranges suggests a new geodynamic model for the evolution of the Arabia-Eurasia continental collision zone. Numerous sedimentary basins in the Alborz mountains and in other locations of the Arabia-Eurasia collision zone record a change from a tensional (transtensional) to a compressional (transpressional) tectonic setting by ~ 36 Ma. I interpret this to reflect the onset of subduction of the stretched Arabian continental lithosphere beneath central Iran, leading to moderate plate coupling and lower- and upper-plate deformation (soft continental collision). The increase in deformation rates in the southern Alborz mountains from ~ 17.5 Ma suggests that significant upper-plate deformation must have started by the early Miocene most likely in response to an increase in degree of plate coupling. I suggest that this was related to the subduction of thicker Arabian continental lithosphere and the consequent onset of hard continental collision. This model reconciles the apparent lag time of 15-20 m.y between the late Eocene to early Oligocene age for the initial Arabia-Eurasia continental collision and the onset of widespread deformation across the collision zone to the north in early to late Miocene time.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-12-03T07:36:31Z No. of bitstreams: 2 Dissertação - Wallas de Souza Castro - 2015.pdf: 6091228 bytes, checksum: 3a8c31295dc00c579cd64b79adafcefb (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-12-03T07:39:02Z (GMT) No. of bitstreams: 2 Dissertação - Wallas de Souza Castro - 2015.pdf: 6091228 bytes, checksum: 3a8c31295dc00c579cd64b79adafcefb (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-12-03T07:39:02Z (GMT). No. of bitstreams: 2 Dissertação - Wallas de Souza Castro - 2015.pdf: 6091228 bytes, checksum: 3a8c31295dc00c579cd64b79adafcefb (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-06-24 / Meanders rivers have sinuous channel with singular dynamic of lateral migration by eroding its concave bank and depositing on its convex bank. This dynamic is able to expand and restore fluvial environments when creates a sedimentary environments complex linked to development of floodplain. The nature of preexistent deposits on floodplain, which are remobilized by lateral migration, is important to interpret deposicional dynamics, being central to the identification evolution of meanders. Heterogeneity of the facies is formed by several cycles of sedimentary evolution through channel migration, generating a succession of deposits with different degree cohesion. These depositional environments affect the continuity migration and the evolution of meanders. It was researched the current evolution of meander and riparian vegetation influence and theirs deposit about lateral migration process on downstream Claro river. It was used aerial photographs, satellite images, facies analysis and pin set on the banks to identify the influences of vegetation and material in the migration processes of meanders. The channel showed high mobility verified by the high amount of migration process in 47 years, due to the planforms diffusion and oxbow lakes and by deposits and paleochannel sedimentary facies. The vegetation has not shown attenuating effect against the bank erosion in the two curves analyzed meanders, erosion rates for the segments with vegetation cover were up to 1,3m ahead of the environments of floodplain. It was found that the intensity of channel migration differs between the curves. Migration advances with little resistance from unconsolidated deposits of the current floodplain, whereas in older deposits, pedogenesis and consistent terraces have hindered lateral advance, due to theirs material. / Rios meandrantes possuem canais fluviais sinuosos com dinâmica particular de migração lateral ao erodir suas margens côncavas e depositar nas margens convexas. Esta dinâmica é capaz de ampliar e renovar os ambientes fluviais ao criar um complexo ambiente sedimentar ligado ao desenvolvimento das planícies fluviais. A natureza dos depósitos preexistentes na planície, que são remobilizados pela migração lateral, é importante para a interpretação da dinâmica deposicional, sendo fundamental para identificação da evolução dos meandros. A heterogeneidade das fácies é formada por vários ciclos de evolução sedimentar pela migração do canal fluvial, gerando uma sucessão de depósitos com grau de coesão diferentes. Os próprios ambientes deposicionais afetam a continuidade da migração lateral e a evolução dos meandros. Investigou-se a evolução atual dos meandros e a influência da vegetação ripária ou ciliar e os seus antigos depósitos sobre os processos de migração lateral do baixo curso do rio Claro. Utilizou-se de fotografias aéreas, imagens orbitais, análise faciológica e pinos fixados nas margens para identificar as influências da vegetação e material nos processos de migração dos meandros. O canal fluvial apresentou alta mobilidade, verificada pela a elevada quantidade de processos de migração em 47 anos, em virtude da difusão de feições marginais e lagoas de meandros (oxbow lakes) e pelos depósitos e fácies sedimentares do paleocanal. A vegetação não apresentou efeito atenuador diante da erosão marginal nas duas curvas de meandros analisadas, as taxas de erosão para os segmentos com cobertura vegetal foram de até 1,3m de avanço sobre os ambientes da planície. Atestou que a intensidade da migração do canal apresenta diferenças entre as curvas. A migração avança com pouca resistência entre depósitos inconsolidados da planície fluvial atual, enquanto que nos depósitos mais antigos, pedogeneizados e consistentes dos terraços, tem avanço lateral dificultado, em função dos seus materiais.

The Petrockstowe and Bovey basins are two similar pull apart (strike slip) basins located on the Sticklepath – Lustleigh Fault Zone (SLFZ) in Devon, SW England. The SLFZ is one of the several faults on the Cornubian Peninsula and may be linked to Variscan structures rejuvenated in Palaeogene times. The bulk of the basins’ fill consists of clays, silts, lignites and sands of Palaeogene age, comparable to the Lough Neagh Basin (Northern Ireland), which is also thought to be part of the SLFZ. In this study a multiproxy approach involving sedimentary facies analysis, palynological analysis, stable carbon isotope (δ13C) analysis and organic carbon palaeothermometer analyses were applied in an attempt to understand the depositional environment in both basins. A negative carbon isotope excursion (CIE) with a magnitude of 2‰ was recorded at ~ 580 m in the siltstone, silty clay to clay lithofacies in the lower part of Petrockstowe Basin, with minimum δ13CTOC values of -28.6‰. The CIE spans a depth of 7 m. Palynological characteristics of this excursion are correlated with the Cogham Lignite in the southern UK, which is the only established PETM section in the UK, and other continental sections to test whether the palynology associated with this CIE can be used to date it. The age model proposed herein correlates the CIE to the Eocene Thermal Maximum -2 (ETM2; ~ 52.5Ma) event. Key pollen and spore assemblages found in the lower Petrockstowe Basin are Monocolpopollenites, Inaperturopollenites, Laevigatisporites, Bisaccate conifer pollen and Tricolporopollenites, which suggest an Eocene age, while those occurring in the upper part of the Petrockstowe and Bovey basins are Arecipites, Inaperturopollenites, Monocolpopollenites, Tricolporopollenites, Sequoiapollenites, and Pompeckjodaepollenites, which have suggested botanical affinities to modern tropical to sub-tropical genera signifying a climate that was frost-free at the time of sediment deposition. This assemblage further suggests that these sediments are Oligocene to middle Oligocene in age. In the upper part of the Petrockstowe Basin, reconstructed mean annual air temperatures (MAT) demonstrate a clear departure from the mean temperature of 24.5oC at 10 m to 19.5oC towards the top of the core, indicating a steady continuous decline similar to the temperature departures seen in the Solent Group in the Hampshire Basin, Isle of Wight, UK which has an established Eocene – Oligocene succession.

Tide-influenced point bars represent a significant proportion of shallow-marine deposits, commonly developed along meandering channels in most backbarrier and estuarine systems. However, sedimentological studies to characterize this type of deposit are still emerging. They often present very heterogeneous internal architectures which development is controlled by the complex flow patterns operating in tidal environments. The study of the sedimentological and morphological characteristics of these features provides better understanding of the hydrodynamic processes that shape coastal systems and control their evolution as well as it contributes to better reservoir potential prediction and production strategy optimization, as tidal point bars may represent hydrocarbon reservoirs in subsurface and their heterogeneous characteristics directly impact reservoir quality. In this study, we investigated six modern tidal point bars located along distinct estuarine tidal channels in Georgia. Using core data, 2D shallow seismic data and current measurements and flow velocity profiles, we discussed the main hydrodynamic controls on sediment transport and distribution, and determined how they affect the morphology, the internal architecture and the sediment distribution within these bars. We confirmed that the influence of fluvial input in tidal channels plays an important role on the development of the morphology and the heterogeneous architecture of point bars as it adds more complexity to the system hydrodynamics, promoting more asymmetric variations in water level fluctuations and huge variations of current velocities. We proved that point bars developed in distinct tide-influenced channels and estuaries, although present very different sedimentary facies distribution, may have sedimentary facies in common, which organization is analogous to surface processes operating at each environment. We demonstrated that differences in tidal asymmetries between the ebb and flood channels produce sedimentological differences between the different parts of the bar. This study showed that tidal point bars present distinct heterogeneous sediment distributions, morphologies and internal architectures that do not conform to the existing theoretical models of fluvial point bars and highlighted that, despite the differences in local hydrodynamic conditions, similarities identified between the different bars permitted us to distinguish the sedimentological responses to regional allogenic events, which can be mistakenly interpreted as sedimentological responses to local autogenic events.

O registro de depósitos quaternários tem aumentado em áreas costeiras da região Amazônica. No entanto, estudos detalhados são ainda necessários visando interpretar seus ambientes de deposição, bem como reconstituir sua evolução ao longo do Quaternário. Em particular, faltam informações sobre a reconstituição das variações do nível relativo do mar ao longo da margem equatorial brasileira de modo a possibilitar a inclusão dessa área em discussões de interesse regional e global enfocando clima, tectônica e eustasia. O presente trabalho representa um esforço de integração de vários tipos de dados, i.e., sedimentologia, estratigrafia, palinologia, diatomácea, datação 14C, \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N, objetivando reconstituir a evolução de paisagens no leste da Ilha do Marajó durante o final do Quaternário. Aspectos ligados a paleoambientes de sedimentação, padrões de vegetação, flutuações climáticas e variação do nível do mar serão abordados. Um total de 98 amostras de sedimentos argilosos e arenosos foi obtido de 85 m de testemunhos coletados com a sonda à percusão Robotic Key System (RKS). Estes testemunhos derivam de cinco poços (TSM4, TSM8, TSM10, TSM11 e TSM12) variando entre 10 e 24 m de profundidade, que foram distribuídos em um transecto proximal-distal correspondente a uma paleomorfologia em funil relacionada a um paleoestuário. As idades registradas variam entre 42.580 (±1430) anos A.P. e 3.184 (±37) anos A.P. Análises de fácies indicaram depósitos de areias grossas a finas, com estratificações plano-paralelas ou cruzadas, e argilas, maciças ou laminadas, intercaladas por camadas heterolíticas. Estas sucessões apresentam padrão granocrescente e/ou granodecrescente ascendente. Valores de \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N sugerem matéria orgânica oriunda de fontes diversas, com contribuição de plantas terrestres (principalmente plantas \'C IND.3\'), bem como fitoplâncton marinho e de água doce, como tipicamente esperado em estuários. A combinação de dados isotópicos, C/N e associações de fácies, permitiu identificar ambientes deposicionais correspondentes a canal fluvial, planície de inundação, canal e planície de maré, bacia central, delta de maré, complexo barreira/inlet e lago. A análise palinológica apresentou mistura de táxons típicos de floresta, de vegetação aberta e de mangue. Em geral, não se detectou mudanças drásticas nos padrões de vegetação no leste da Ilha de Marajó nos últimos 40.000 anos. A assembléia polínica foi melhor representada nos testemunhos dos poços TSM8 e TSM4. Neste último, as oito amostras basais (i.e., MR248 a MR258) registraram tipos arbóreos, como Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Na vegetação de mangue, Rhizophora constituiu o gênero mais comum, enquanto Poacea e Cyperaceae foram os mais freqüentes entre os táxons de ervas. A proporção entre pólen de floresta e de ervas mostrou-se constante em todas as zonas inseridas no Pleistoceno Tardio. Porém, aumento significativo de tipos herbáceos, com espécies pioneiras representadas por Alchornea e Moraceae/Urticaceae, foi registrado a partir de 6.790 (±60) anos A.P. Portanto, esta é a idade considerada para o estabelecimento de vegetação aberta do leste da Ilha de Marajó. Análises de diatomáceas dos testemunhos TSM8, TSM10 e TSM11, onde não houve registro polínico, foram consistentes com o valores isotópicos e de C/N, indicando intervalos com maior contribuição de matéria orgânica derivada de fitoplâncton marinho. Diatomáceas identificadas nestes testemunhos são, em grande parte, espécies e gêneros marinhos, como Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp e Thalassiosira sp. Táxons continentais como Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium e Pinnularia foram registrados em uma única amostra no topo do testemunho TSM8. Informações faciológicas, juntamente com dados isotópicos, elementares, \'ANTPOT.14 C\', palinológicos e de diatomáceas, são consistentes com a existência de paleoestuário com domínio de onda no Pleistoceno Tardio e Holoceno no nordeste da Ilha do Marajó, previamente ao estabelecimento do lago Arari. As fases iniciais propostas para a interrupção do influxo fluvial para o paleoestuário Arari coincidem com a formação de vegetação aberta na ilha e a conseqüente diminuição das áreas de mangue no Holoceno médio. O efeito da tectônica regional parece ter sido de grande contribuição nas mudanças da paisagem do Marajó durante o Pleistoceno e Holoceno. Divergência do nível relativo do mar proposto para a Ilha do Marajó em relação ao padrão global, combinado com o aumento de registro de atividade tectônica no Pleistoceno Tardio e Holoceno, levaram à hipótese de que eventos transgressivos poderiam ter sido devidos à subsidência tectônica, e não à eustasia. A transgressão registrada antes de 29.000 anos A.P. ocorreu simultaneamente à forte tendência de queda eustástica após o Último Máximo Interglacial. Além disto, a transgressão holocênica no Marajó é registrada entre 9.000 e 5.000 anos A.P., portanto tendo início antes do pico transgressivo global do Holoceno médio. Durante este período de ascensão eustática, o nível relativo do mar na Ilha de Marajó começou a estabilizar, processo este que culminou com a significativa progradação da costa no final deste período. Da mesma forma, é improvável que a abertura da vegetação, com aumento significativo em espécies herbáceas, registrada a partir do Holoceno médio tenha efeito climático, uma vez que ela ocorreu simultaneamente à mudança de clima relativamente mais árido para relativamente mais úmido. A hipótese mais provável é que vegetação aberta tenha se estabelecido no leste da Ilha de Marajó em função de mudança hidrológicas, talvez promovida pela subsidência tectônica e subseqüente estabilização, culminada com a recente progradação da linha de costa. / The record of Quaternary deposits has increased in coastal areas of the Amazon region. However, detailed studies are still needed aiming to interpret their depositional environments, as well as reconstruct their evolution throughout the Quaternary. In particular, there is a lack of information about the reconstruction of relative sea level along the Brazilian equatorial margin to enable the inclusion of this area in discussions of regional and global interest focusing climate, tectonics and eustasy. The present work represents an effort to integrate vários types of data, i.e., sedimentology, stratigraphy, palinology, diatoms, \'ANTPOT.14 C\' dating, \'ANTPOT.13 C\', \'delta\' \'ANTPOT.15 N\' and C/N, aiming to reconstruct landscape evolution in eastern Marajó Island during the late Quaternary. Aspects related to sedimentary paleoenvironments, vegetation patterns, climate fluctuations and relative sea level changes will be approached. A total of 98 samples of muddy and sandy sediments was obtained from 85 m of cores collected with a percusion Robotic Key System (RKS). These cores derive from five drills (TSM12, TSM11, TSM10, TSM8 and TSM4) that reached depths ranging from 10 to 24 m, which were distributed in a proximal-distal transect corresponding to a funnel paleomorphology related to a paleoestuary. Reported ages range from 42, 580 ± (1430) \'ANTPOT.14 C\' yr B.P and 3,184 ± (37) \'ANTPOT.14 C\' yr B.P. Facies analysis showed parallel laminated or cross stratified, fine- to coarse-grained sands, massive or laminated muds and heterolithic deposits. These deposits are often arranged into coarsening and fining upward cycles. Values of \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' and C/N suggest organic matter from several sources, with contributions from terrestrial plants (mainly \'C IND.3\' plants), as well as freshwater and marine phytoplankton, as typically expected in estuaries. Combination of isotope data, C/N and facies associations led to identify depositional settings corresponding to fluvial channel, floodplain, tidal channel/tidal flat, central basin, tidal delta, inlet/barrier complex and lagoon. Pollen analysis showed a mixture of taxa typical of forest, open vegetation and mangrove. In general, drastic changes in vegetation patterns were not detected in eastern Marajó Island in the last 40,000 years. Pollen assemblages were better represented in cores TSM8 and TSM4. In the latter, the eight basal samples (i.e., MR248 to MR258) recorded arboreal types sucha as Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Among mangrove vegetation, Rhizophora constitutes the most common genera, while Poacea and Cyperacea were the most frequent among the herb taxa. The proportion between forest and herb pollen was constant in all zones inserted in the Late Pleistocene. However, significant increase of herbaceous pollen types, with pioneer species represented by Alchornea and Moraceae/Urticaceae, were recorded from 6,790 (±60) \'ANTPOT.14 C\' yr B.P. Thus, this is the age considered for the establishment of the open vegetation of eastern Marajó Island. Diatom analyses of the cores TSM8, TSM10 e TSM11, which did not record pollen, were consistent with the isotope and C/N values, indicating intervals with higher contribution of organic matter derived from marine phytoplankton. Diatoms identified from these cores are, in great part, marine species and genera, such as Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp and Thalassiosira sp. Continental taxa such as Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium and Pinnularia were recorded only in one sample from the top of the core TSM8. Facies infomration, together with isotope, elementar, \'ANTPOT.14 C\', palinological, and diatom data, are consistent with the existence of a wave-dominated paleoestuary during the Late Pleistocene and Holocene in northeastern Marajó Island, previously to the establishment of Lake Arari. The initial stages proposed for the interruption of fluvial inflow to the paleoestuary Arari coincide with the formation of open vegetation in the island and the consequent reduction of mangrove areas at the mid Holocene. The effect of regional tectonics seems to have been of a great contribution to change the Marajó landscape during Pleistocene and Holocene. Divergency of relative sea level proposed for the Marajó Island with respect to the global pattern, combined with the increased record of tectonic activity in the Late Pleistocene and Holocene, led to the hypothesis of successive transgressions linked to tectonic subsidence as opposed to eustary. The transgression recorded before nearly 29,000 yr B.P. took place simultaneously to the pronounced tendency of sea level drop after the Last Interglacial Maximum. Additionally, the Holocene transgression in Marajó is recorded between 9,000 and 5,000 yr. B.P., thus it initiated before the global transgressive peak of the mid Holocene. During this period of eustatic rise, the relative sea level in Marajó Island started to stabilize, a process that culminated with a significant coast progradation at the end of this period. It is also unlikely that the change to open vegetation recorded from the mid Holocene had a climatic response, as this change took place simultaneously to climate fluctuation from relatively more arid to relatively more humid. The most likely hypothesis is that the open vegetation became established in eastern Marajó Island in response to hydrological changes, perhaps promoted by tectonic subsidence and subsequent estabilization, culminated with the recent coastline progradation.

L’objectif de ce travail est de reconstituer les changements de la dynamique hydrosédimentaire de la Loire en fonction des variations climatiques globales et régionales depuis l’Holocène Moyen (~7 ka), dans un contexte de ralentissement et de stabilisation de la remontée du niveau marin. Le rôle des aménagements anthropiques de l’estuaire interne depuis le début du XXème siècle, a été également considéré. Dans cet objectif, les séquences sédimentaires étudiées ont été prélevées le long d’un continuum terre-mer entre l’estuaire interne de la Loire et la partie septentrionale du Golfe de Gascogne, en passant par les paléovallées incisées présentes à l’embouchure actuelle.L’emboitement des dimensions temporelle et spatiale fait l’unicité de ce travail de recherche à l’échelle de la Loire mais également sa complexité. Afin de déconvoluer les différents signaux enregistrés, nous avons entrepris une approche analytique combinant des données sédimentologiques, micro-paléontologiques (foraminifères benthiques) et géochimiques, le tout dans un cadre chronologique contraint par des datations 14Cet 210Pb/137Cs. Nos résultats montrent que le ralentissement de la montée des eaux a joué un rôle majeur dans le façonnement du paysage estuarien et par conséquence, dans la chenalisation du flux terrigène vers le large. Ce flux terrigène est également modulé à plus grande échelle par les forçages climatiques internes et externes (e.g., Oscillation Nord Atlantique, forçage solaire) affectant à la fois le bassin versant, l’occurrence des tempêtes au large ainsi que la circulation océanique de surface. Enfin, la partie la plus récente de nos archives sédimentaires estuariennes enregistre l’impact des aménagements humains qui ont profondément modifié la morphologie de l’estuaire interne depuis le début du XXème siècle. / The aim of this work is to reconstruct changes in the hydro-sedimentary dynamics of the Loire River according to global and regional climatic variations since the Middle Holocene (~ 7 ka), in a general context of slowing down of sea-level rise. The impact of the recent human settlements undertaken in the internal Loire estuary since the beginning of the 20th century is also considered. To achieve this objective, the studied sedimentary sequences were collected along a land-sea continuum from the internal estuary, to the incised paleovalleys off the present-day river mouth, until the northern part of the Bay of Biscay (South Brittany). The imbrication of both temporal and spatial dimensions makes the originality of this research on the scale of the Loire River, but also its complexity. In order to deconvolute the various recorded signals, we used a multiproxy approach combining sedimentological, micropaleontological (benthic foraminifera) and geochemical analyses, within a chronological framework constrained by 14C and 210Pb/137Cs dating. Our results show that the Middle to Late Holocene slowing down of sea-level rise plays a major role in shaping the estuarine landscape and in the channelization of the terrigenous flow towards the ocean. At the same time, this terrigenous flow is modulated on a larger scale by internal and external climatic forcing (e.g., North Atlantic Oscillation, solar forcing) controlling humidity over the Loire River catchment area, the occurrence of storms and ocean surface circulation. The most recent parts of our estuarine sedimentary sequences record the impact of human settlements since the beginning of the 20th century modifying significantly the morphology of the inner estuary and the location of the main river channel.

Il est débattue sur le temps closural finale de l'océan paléo-asiatique et la position. Certains géologues ont préconisé la suture "Solonker" marque la zone closural finale du Permien , tandis que d'autres insistent sur le fait Paléozoïque milieu. Nos trois domaines d'étude, le Hongqi , le Ondor Somme et le Mandula ont essentiel et important de résoudre ces controverses. Les unités litho-tectonique reconnus dans le domaine Hongqi-Ondor Sum sont le mélange Belt de Hongqi-Ondor Sum, la Belt de l'arc Bainaimiao, craton du Nord de Chine et les roches sédimentaires post-orogéniques. Le mélange Belt de Hongqi-Ondor Sum connu déformation ductile en deux phases et une phase de la déformation ductile-fragile. D1 est responsable de la S1 foliation, linéation minérale L1, et intrafolial pli F1. Les critères cinématiques indiquent un sens cisaillement de top-to-the-NW. D2 est caractérisée par divers taille de plis asymétriques avec axe presque NE correspondant à la poussée NW cisaillement. D3 formé le cadre régional dans le Hongqi et les zones Ondor Sum. La zone Mandula contient les sédiments olistostrome, les sédiments turbiditiques et roches volcanosédimentaires. Grains de zircons détritiques dans des échantillons sédimentaires indiquent la zone d'étude Mandula reçu des matériaux d'arc Bainaimiao et matières contemporaines de l'éruption volcanique du Permien. Les sédiments et les roches volcaniques dans la région Mandula soumettent un NW-SE ou près de N-S du raccourcissement. Les données géologiques indiquent qu'une subduction et collsion dans Paléozoïque inférieur, et rifting et fermeture rift dans Palezoic supérieur. Les fragments ophiolitiques "Solonker" sont en effet olistostrome. Composants ophiolitiques typiques ne sont pas observés dans la région Mandula. / It is hotly debated about the final closural time and position of the Paleo-Asian Ocean. Some geologists advocated the “Solonker” suture marks the final closural zone in Permian, whereas others insist in middle Paleozoic. Our three study areas, the Hongqi, the Ondor Sum and the Mandula is essential and important to solve those controversies. The litho-tectonic units recognized in the Hongqi-Ondor Sum area include the Hongqi-Ondor Sum mélange belt, the Bainaimiao arc belt, North China Craton and post-orogenic unconformably sedimentary rocks. The Hongqi-Ondor Sum mélange belt experienced two phase ductile deformation and one phase ductile-brittle deformation. D1 is responsible for the regional greenschist foliation S1, elongated mineral lineation L1, and intrafolial fold F1. The kinematic criteria indicates a top-to-the-NW shearing sense. D2 is characterized by various sized of unsymmetrical folds with nearly NE axis corresponding to the NW thrust shearing. D3 formed the regional framework in the Hongqi and the Ondor Sum areas. The Mandula area contains olistostrome sediments, turbiditic sediments and volcano-sedimentary rocks. Detrital zircon grains in sedimentary samples argue the Mandula study area received the southern Bainaimiao arc materials and coeval Permian volcanic erupting materials nearby. The sediments and volcanic rocks in Mandula area subject a nearly NW-SE or N-S compressional shortening. The geological data support that an Early Paleozoic subduction and collsioan, Late Palezoic rifting and rift closure model. The so called “Solonker” ophiolitic fragments indeed are olistostrome. Typical ophiolite components are not observed in the Mandula area.

It is hotly debated about the final closural time and position of the Paleo-Asian Ocean. Some geologists advocated the "Solonker" suture marks the final closural zone in Permian, whereas others insist in middle Paleozoic. Our three study areas, the Hongqi, the Ondor Sum and the Mandula is essential and important to solve those controversies. The litho-tectonic units recognized in the Hongqi-Ondor Sum area include the Hongqi-Ondor Sum mélange belt, the Bainaimiao arc belt, North China Craton and post-orogenic unconformably sedimentary rocks. The Hongqi-Ondor Sum mélange belt experienced two phase ductile deformation and one phase ductile-brittle deformation. D1 is responsible for the regional greenschist foliation S1, elongated mineral lineation L1, and intrafolial fold F1. The kinematic criteria indicates a top-to-the-NW shearing sense. D2 is characterized by various sized of unsymmetrical folds with nearly NE axis corresponding to the NW thrust shearing. D3 formed the regional framework in the Hongqi and the Ondor Sum areas. The Mandula area contains olistostrome sediments, turbiditic sediments and volcano-sedimentary rocks. Detrital zircon grains in sedimentary samples argue the Mandula study area received the southern Bainaimiao arc materials and coeval Permian volcanic erupting materials nearby. The sediments and volcanic rocks in Mandula area subject a nearly NW-SE or N-S compressional shortening. The geological data support that an Early Paleozoic subduction and collsioan, Late Palezoic rifting and rift closure model. The so called "Solonker" ophiolitic fragments indeed are olistostrome. Typical ophiolite components are not observed in the Mandula area.

O registro de depósitos quaternários tem aumentado em áreas costeiras da região Amazônica. No entanto, estudos detalhados são ainda necessários visando interpretar seus ambientes de deposição, bem como reconstituir sua evolução ao longo do Quaternário. Em particular, faltam informações sobre a reconstituição das variações do nível relativo do mar ao longo da margem equatorial brasileira de modo a possibilitar a inclusão dessa área em discussões de interesse regional e global enfocando clima, tectônica e eustasia. O presente trabalho representa um esforço de integração de vários tipos de dados, i.e., sedimentologia, estratigrafia, palinologia, diatomácea, datação 14C, \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N, objetivando reconstituir a evolução de paisagens no leste da Ilha do Marajó durante o final do Quaternário. Aspectos ligados a paleoambientes de sedimentação, padrões de vegetação, flutuações climáticas e variação do nível do mar serão abordados. Um total de 98 amostras de sedimentos argilosos e arenosos foi obtido de 85 m de testemunhos coletados com a sonda à percusão Robotic Key System (RKS). Estes testemunhos derivam de cinco poços (TSM4, TSM8, TSM10, TSM11 e TSM12) variando entre 10 e 24 m de profundidade, que foram distribuídos em um transecto proximal-distal correspondente a uma paleomorfologia em funil relacionada a um paleoestuário. As idades registradas variam entre 42.580 (±1430) anos A.P. e 3.184 (±37) anos A.P. Análises de fácies indicaram depósitos de areias grossas a finas, com estratificações plano-paralelas ou cruzadas, e argilas, maciças ou laminadas, intercaladas por camadas heterolíticas. Estas sucessões apresentam padrão granocrescente e/ou granodecrescente ascendente. Valores de \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' e C/N sugerem matéria orgânica oriunda de fontes diversas, com contribuição de plantas terrestres (principalmente plantas \'C IND.3\'), bem como fitoplâncton marinho e de água doce, como tipicamente esperado em estuários. A combinação de dados isotópicos, C/N e associações de fácies, permitiu identificar ambientes deposicionais correspondentes a canal fluvial, planície de inundação, canal e planície de maré, bacia central, delta de maré, complexo barreira/inlet e lago. A análise palinológica apresentou mistura de táxons típicos de floresta, de vegetação aberta e de mangue. Em geral, não se detectou mudanças drásticas nos padrões de vegetação no leste da Ilha de Marajó nos últimos 40.000 anos. A assembléia polínica foi melhor representada nos testemunhos dos poços TSM8 e TSM4. Neste último, as oito amostras basais (i.e., MR248 a MR258) registraram tipos arbóreos, como Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Na vegetação de mangue, Rhizophora constituiu o gênero mais comum, enquanto Poacea e Cyperaceae foram os mais freqüentes entre os táxons de ervas. A proporção entre pólen de floresta e de ervas mostrou-se constante em todas as zonas inseridas no Pleistoceno Tardio. Porém, aumento significativo de tipos herbáceos, com espécies pioneiras representadas por Alchornea e Moraceae/Urticaceae, foi registrado a partir de 6.790 (±60) anos A.P. Portanto, esta é a idade considerada para o estabelecimento de vegetação aberta do leste da Ilha de Marajó. Análises de diatomáceas dos testemunhos TSM8, TSM10 e TSM11, onde não houve registro polínico, foram consistentes com o valores isotópicos e de C/N, indicando intervalos com maior contribuição de matéria orgânica derivada de fitoplâncton marinho. Diatomáceas identificadas nestes testemunhos são, em grande parte, espécies e gêneros marinhos, como Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp e Thalassiosira sp. Táxons continentais como Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium e Pinnularia foram registrados em uma única amostra no topo do testemunho TSM8. Informações faciológicas, juntamente com dados isotópicos, elementares, \'ANTPOT.14 C\', palinológicos e de diatomáceas, são consistentes com a existência de paleoestuário com domínio de onda no Pleistoceno Tardio e Holoceno no nordeste da Ilha do Marajó, previamente ao estabelecimento do lago Arari. As fases iniciais propostas para a interrupção do influxo fluvial para o paleoestuário Arari coincidem com a formação de vegetação aberta na ilha e a conseqüente diminuição das áreas de mangue no Holoceno médio. O efeito da tectônica regional parece ter sido de grande contribuição nas mudanças da paisagem do Marajó durante o Pleistoceno e Holoceno. Divergência do nível relativo do mar proposto para a Ilha do Marajó em relação ao padrão global, combinado com o aumento de registro de atividade tectônica no Pleistoceno Tardio e Holoceno, levaram à hipótese de que eventos transgressivos poderiam ter sido devidos à subsidência tectônica, e não à eustasia. A transgressão registrada antes de 29.000 anos A.P. ocorreu simultaneamente à forte tendência de queda eustástica após o Último Máximo Interglacial. Além disto, a transgressão holocênica no Marajó é registrada entre 9.000 e 5.000 anos A.P., portanto tendo início antes do pico transgressivo global do Holoceno médio. Durante este período de ascensão eustática, o nível relativo do mar na Ilha de Marajó começou a estabilizar, processo este que culminou com a significativa progradação da costa no final deste período. Da mesma forma, é improvável que a abertura da vegetação, com aumento significativo em espécies herbáceas, registrada a partir do Holoceno médio tenha efeito climático, uma vez que ela ocorreu simultaneamente à mudança de clima relativamente mais árido para relativamente mais úmido. A hipótese mais provável é que vegetação aberta tenha se estabelecido no leste da Ilha de Marajó em função de mudança hidrológicas, talvez promovida pela subsidência tectônica e subseqüente estabilização, culminada com a recente progradação da linha de costa. / The record of Quaternary deposits has increased in coastal areas of the Amazon region. However, detailed studies are still needed aiming to interpret their depositional environments, as well as reconstruct their evolution throughout the Quaternary. In particular, there is a lack of information about the reconstruction of relative sea level along the Brazilian equatorial margin to enable the inclusion of this area in discussions of regional and global interest focusing climate, tectonics and eustasy. The present work represents an effort to integrate vários types of data, i.e., sedimentology, stratigraphy, palinology, diatoms, \'ANTPOT.14 C\' dating, \'ANTPOT.13 C\', \'delta\' \'ANTPOT.15 N\' and C/N, aiming to reconstruct landscape evolution in eastern Marajó Island during the late Quaternary. Aspects related to sedimentary paleoenvironments, vegetation patterns, climate fluctuations and relative sea level changes will be approached. A total of 98 samples of muddy and sandy sediments was obtained from 85 m of cores collected with a percusion Robotic Key System (RKS). These cores derive from five drills (TSM12, TSM11, TSM10, TSM8 and TSM4) that reached depths ranging from 10 to 24 m, which were distributed in a proximal-distal transect corresponding to a funnel paleomorphology related to a paleoestuary. Reported ages range from 42, 580 ± (1430) \'ANTPOT.14 C\' yr B.P and 3,184 ± (37) \'ANTPOT.14 C\' yr B.P. Facies analysis showed parallel laminated or cross stratified, fine- to coarse-grained sands, massive or laminated muds and heterolithic deposits. These deposits are often arranged into coarsening and fining upward cycles. Values of \'delta\'\'ANTPOT.13 C\', \'delta\'\'ANTPOT.15 N\' and C/N suggest organic matter from several sources, with contributions from terrestrial plants (mainly \'C IND.3\' plants), as well as freshwater and marine phytoplankton, as typically expected in estuaries. Combination of isotope data, C/N and facies associations led to identify depositional settings corresponding to fluvial channel, floodplain, tidal channel/tidal flat, central basin, tidal delta, inlet/barrier complex and lagoon. Pollen analysis showed a mixture of taxa typical of forest, open vegetation and mangrove. In general, drastic changes in vegetation patterns were not detected in eastern Marajó Island in the last 40,000 years. Pollen assemblages were better represented in cores TSM8 and TSM4. In the latter, the eight basal samples (i.e., MR248 to MR258) recorded arboreal types sucha as Alchornea, Euphorbiaceae, Euterpe, Malpighiaceae e Moraceae/Urticaceae. Among mangrove vegetation, Rhizophora constitutes the most common genera, while Poacea and Cyperacea were the most frequent among the herb taxa. The proportion between forest and herb pollen was constant in all zones inserted in the Late Pleistocene. However, significant increase of herbaceous pollen types, with pioneer species represented by Alchornea and Moraceae/Urticaceae, were recorded from 6,790 (±60) \'ANTPOT.14 C\' yr B.P. Thus, this is the age considered for the establishment of the open vegetation of eastern Marajó Island. Diatom analyses of the cores TSM8, TSM10 e TSM11, which did not record pollen, were consistent with the isotope and C/N values, indicating intervals with higher contribution of organic matter derived from marine phytoplankton. Diatoms identified from these cores are, in great part, marine species and genera, such as Actinoptychus splendens, Paralia sulcata, Coscinodiscus radiatus, Coscinodiscus sp and Thalassiosira sp. Continental taxa such as Actinella sp1, Aulacoseira, Eunotia zygodon, Desmogonium and Pinnularia were recorded only in one sample from the top of the core TSM8. Facies infomration, together with isotope, elementar, \'ANTPOT.14 C\', palinological, and diatom data, are consistent with the existence of a wave-dominated paleoestuary during the Late Pleistocene and Holocene in northeastern Marajó Island, previously to the establishment of Lake Arari. The initial stages proposed for the interruption of fluvial inflow to the paleoestuary Arari coincide with the formation of open vegetation in the island and the consequent reduction of mangrove areas at the mid Holocene. The effect of regional tectonics seems to have been of a great contribution to change the Marajó landscape during Pleistocene and Holocene. Divergency of relative sea level proposed for the Marajó Island with respect to the global pattern, combined with the increased record of tectonic activity in the Late Pleistocene and Holocene, led to the hypothesis of successive transgressions linked to tectonic subsidence as opposed to eustary. The transgression recorded before nearly 29,000 yr B.P. took place simultaneously to the pronounced tendency of sea level drop after the Last Interglacial Maximum. Additionally, the Holocene transgression in Marajó is recorded between 9,000 and 5,000 yr. B.P., thus it initiated before the global transgressive peak of the mid Holocene. During this period of eustatic rise, the relative sea level in Marajó Island started to stabilize, a process that culminated with a significant coast progradation at the end of this period. It is also unlikely that the change to open vegetation recorded from the mid Holocene had a climatic response, as this change took place simultaneously to climate fluctuation from relatively more arid to relatively more humid. The most likely hypothesis is that the open vegetation became established in eastern Marajó Island in response to hydrological changes, perhaps promoted by tectonic subsidence and subsequent estabilization, culminated with the recent coastline progradation.