Cloudina foi o primeiro fóssil de um organismo biomineralizado encontrado no final do Ediacarano. Também figuram nesse período Corumbella, Namacalathus, Sinotubulites e Namapoikia entre a biota esquelética. No Grupo Corumbá (MS), em carbonatos e pelitos da Formação Tamengo, ocorrem os fósseis de Cloudina e Corumbella, respectivamente. Este trabalho teve como objetivo analisar questões paleobiológicas referentes ao fóssil esquelético Cloudina, como seu contexto tafonômico, taxonômico e paleoecológico. Análises geoquímicas e de microestrutura foram realizadas para permitir melhor compreensão da esqueletogênese desse fóssil. Para tanto, foram utilizadas técnicas paleométricas, como: Espectroscopia Raman, Energia Dispersiva de Raios-x (EDS), Fluorescência de Raios-x por Energia Dispersiva (EDXRF) e Fluorescência de Raios-x Sincrotron (XRF-SRS) - para as análises de composição química e mineralógica; e Microscopia Eletrônica de Varredura (MEV) e Microtomografia Computadorizada (MicroCT) - para imageamento de microestruturas e feições morfológicas não visíveis na superfície, respectivamente. As análises tafonômicas de orientação revelaram padrões NNE-SSW e NE-SW, assim como WNW-ESSE, sugerindo correntes que variaram desde quase paralelas, até, possivelmente, perpendiculares com relação à linha de costa. As alterações tafonômicas encontradas incluem fragmentação das porções externas da concha, deformação plástica, neomorfismo, dissolução da parede e presença de calcita eodiagenética entre as abas dos funis. Esse contexto tafonômico indica uma deposição por retrabalhamento dos bioclastos e sugere que informações morfológicas, como diâmetro, são alteradas tafonomicamente. A análise biométrica das amostras alóctones indicou bimodalidades para populações estatísticas de Cloudina considerando 1, 2, 3 ou 4 camadas em corte transversal, e conjuntamente com a distribuição de tamanho normal para uma assembleia autóctone sugere uma mistura de populações originais de tamanhos diferentes. Esses resultados trazem implicações para a taxonomia de Cloudina para esses depósitos, definindo C. lucianoi como tafotáxon. A análise da amostra autóctone demonstra a ocorrência de Cloudina com biolaminitos e microfósseis e fortalecem a interpretação de que esse metazoário vivia em habitats associados com microbialitos. A presença de goethita e calcita eodiagenética entre as abas de Cloudina, assim como microesferas silicificadas sugerem a presença de uma matéria orgânica nessas porções externas do organismo que podem estar relacionadas com o desenvolvimento de possíveis biofilmes simbiontes. A posição de vida horizontal verificada para Cloudina na amostra autóctone indica a versatilidade de modo de vida dessa organismo quando comparada a ocorrências de espécimes verticais em outras localidades. Nessa mesma amostra, indivíduos com mudanças na direção de crescimento podem ser resultantes da proximidade com outros espécimes, o que sugere capacidade sensoriais que auxiliariam na ocupação do substrato. Os resultados de MEV demonstraram que geralmente a microestrutura não está preservada, mas em alguns casos pode-se notar microgrânulos de calcita e um padrão reticulado. Conjuntamente com MEV, em análises petrográficas foram observadas duas camadas formando a parede de Cloudina. As análises geoquímicas de EDS e Raman demonstraram a presença de carbono na concha e corroboram trabalhos anteriores que postularam uma concha rica em matéria orgânica. As quantidades de Mg% e MgO% verificadas por EDS caracterizaram os fósseis da Formação Tamengo como de baixo teor de magnésio e fitting de bandas de calcita em espectros Raman fortalecem essa interpretação. Mesmo assim, alterações diagenéticas de estabilização por perda de Mg podem ter ocorrido. Os resultados de XRF-SRS mostraram que não há variação de Sr maior que 1000 ppm entre o fóssil e a rocha, indicando que, pelo menos, a mineralogia da concha não era aragonítica. Sendo assim, o presente trabalho traz novos cenários para a paleobiologia de Cloudina da Fm. Tamengo: Cloudina lucianoi é considerado como tafotáxon pelo contexto tafonômico e análise biométrica, indica ambientes de vida associados com microbialitos e possíveis cianobactérias, relações simbióticas podem ter ocorrido entre esse metazoário e biofilmes, é inferido modo de vida horizontal a sub-horizontal, é sugerido comportamentos de competição por espaço, a esqueletogênese de Cloudina é caracterizada por funis compostos por uma parede com duas camadas, rica em matéria orgânica e com microgrânulos de calcita. / Cloudina was the first fossil of a biomineralized organism found in latest Ediacaran. Also in this period, there was Corumbella, Namacalathus, Sinotubulites and Namapoikia within the skeletal biota. In the Corumbá Group (MS), in carbonates and pelites of Tamengo Formation, occur the fossils of Cloudina and Corumbella, respectively. This work aims to analyze paleobiological questions regarding Cloudina, such as its taphonomical, taxonomical and paleoecological context. Geochemical and microstructural analyses were performed to better understand the skeletogenesis of this fossil. For this, were utilized paleometrical techniques, such: Raman Spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Fluorescence Synchrotron based (XRF-SRS) - for chemical and mineralogical analyses; and Scanning Electron Microscopy (SEM) and Computerized Microtomography (MicroCT) - for imaging of non-visible surficial microstructures and morphological attributes. The taphonomical analyses of orientation revealed NNE-SSW and NE-SW, as well as WNW-ESSE patterns, indicating currents that varied from almost parallel, to, possibly, perpendicular with relation to the ancient coastline. The taphonomical alterations include fragmentation of the external portions of the flares, plastic deformation, neomorphism, dissolution of the wall and the presence of eodiagenetic calcite between the flares of the funnels. This taphonomical context suggests a deposition by reworking and indicates that morphological information, such as diameter, is taphonomical altered. The biometrical analysis for the allochthonous specimens indicated bimodality for the statistical populations of Cloudina considering one, two, three or four layers in cross section, and together with the normal size distribution for the autochthonous assemblage suggest a mixture of original populations of different sizes. These results bring implications to the taxonomy of Cloudina, defining C. lucianoi as a taphotaxon. The study of the autochthonous assemblage demonstrated the occurrence of Cloudina with biolaminites and microfossils, and strengthens the interpretation that this metazoan lived in habitats associated with microbialites. The presence of goethite and eodiagenetic calcite between the flares of Cloudina, as well as silicified microspheres suggest the presence of organic matter in these external portions of the organism that can be related to de development of possibly symbiotic biofilms. The horizontal life position verified for Cloudina in the autochthonous assemblage together with occurrences in other localities of vertical specimens indicates the versatility of the life modes of this organism. Also in this sample, individuals with changes in the growing direction could be resultant of the proximity with other specimens, suggesting sensorial capacities, which assisted in the occupation of the substrate. SEM results demonstrated that often the microstructure is not preserved, but in some cases can be noted microgranules of calcite and a reticulate pattern. Allied with SEM, in petrographic sections were observed two layers forming the wall of Cloudina. EDS and Raman analysis showed the presence of carbon in the carapace and corroborate previous studies that postulated a shell with high amount of organic matter. Quantities of Mg% and MgO% verified by EDS characterized the fossils as low-magnesian calcites and fitting of calcite bands from Raman spectra strengthen this interpretation. Nevertheless, diagenetical alterations of stabilization by loss of Mg could have occurred. The results from XRF-SRS showed that there is no great variation in the Sr content between the fossil and the rock matrix, indicating that the mineralogy was not aragonitic. Thus, this work brings new scenarios for the paleobiology of Cloudina from the Tamengo Fm: Cloudina lucianoi is considered as a taphotaxon by the taphonomical and biometrical results, indicates habitats associated with microbialites and possible cyanobacteria, symbiotic relations could have occurred between this metazoan and biofilms, is inferred a horizontal to sub-horizontal life position and behaviors for space competition, the skeletogenesis of Cloudina is characterized by funnels composed of a wall with two layers, rich in organic matter and with microgranules of calcite.

The analysis and interpretation of Vendobionta morphology is critical to elucidating a range of issues about their ontogeny and evolution, as well as life habits. These analyses, however, are complicated because these organisms are often morphologically enigmatic and defy ready categorization within modern taxonomic schemes. This study delves into the morphology of one of these problematic groups: Pteridinium. Specimens were investigated from two localities, Namibia and North Carolina, using geometric morphometrics. The landmark data, which was analyzed to compare specimens based on locality, taphonomy, and preservation, were subjected to three statistical tests: Principle Components Analysis, Procrustes shape analyses, and Foote's disparity test. All tests revealed no distinct clustering within or by either group due to any of the variables. All variables plotted within the same 95% confidence ellipses, displaying a lack of statistical support for the distinctness of these groups. Therefore, the most parsimonious reason for the lack of differences observed by these two groups stem from them being part of the same morphological group, a conclusion that places into question the validity of the inclusion of two separate species in the genus Pteridinium.

The western United States Deep Spring and Wood Canyon formations contain a variety of late Ediacaran fossils, representing the enigmatic Ediacara biota and a metazoan worm-like fauna. The latter, dubbed ?Wormworld?, is comprised of a number of tube-dwelling organisms whose tubes were preserved through pervasive pyritization and carbonaceous compressions, as well as abundant horizontal burrows and grazing traces. One particular site, within Ancient Bristlecone Pine Forest presents a challenge that is not faced at the other localities, as it contains abundant tube-shaped fossils that are lacking in morphological characteristics due to poor preservation. Through investigations into what remains of the fossils and the potential preservational pathways that could produce such fossils, it is possible to use the findings to identify additional tube worm assemblages that may have been overlooked due to the assumed restriction on exceptional preservation based on sedimentology. Alternatively, trace fossils in the area appear to be more readily preserved and abundant, allowing for investigations into trends in frequency and faunal occurrences leading into the Cambrian Explosion. These traces and the trace maker activities are of a particular interest, as they represent the first communities of established bioturbators, which helped oxygenate the seafloor and mix the previously stratified microbial mat-rich substrate. The trace fossils on the surface of the beds represented ichnotaxa that are well-known in Cambrian deposits. However, petrographic thin sectioning revealed an unexpected fossil, Lamonte trevallis, previously only reported from South China. The presence of Lamonte trevallis is evidence for more advanced, complex Cambrian-like feeding behaviors occurring prior to the Precambrian?Cambrian boundary. The diversity of the Ediacaran fossils from the western United States places it among the established Ediacaran exceptional preservation localities and justifies the designation of the Deep Spring/Wood Canyon assemblage as an Ediacaran Lagerst?tte.

This thesis makes several contributions to improve our understanding of the Neoproterozoic Paleobiology. In chapter 1, a comprehensive quantitative analysis of the Ediacara fossils indicates that the oldest Ediacara assemblage "the Avalon assemblage" already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea and Nama assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. The Avalon morphospace expansion mirrors the Cambrian explosion, and both may reflect similar underlying mechanisms. Chapter 2 describes problematic macrofossils collected from the Neoproterozoic slate of the upper Zhengmuguan Formation in North China and sandstone of the Zhoujieshan Formation in Chaidam. Some of these fossils were previously interpreted as animal traces. Our study of these fossils recognizes four genera and five species. None of these taxa can be interpreted as animal traces. Instead, they are problematic body fossils of unresolved phylogenetic affinities. Chapter 3 reports stable isotopes of the Zhamoketi cap dolostone atop the Tereeken diamictite in the Quruqtagh area, eastern Chinese Tianshan. Our new data indicate that carbonate associated sulfate (CAS) abundance decreases rapidly in the basal cap dolostone and δ34SCAS composition varies between +9â ° and +15â ° in the lower 2.5 m. In the overlying interval, CAS abundance remains low while δ34SCAS rises ~5â ° and varies more widely between +10â ° and +21â °. δ34Spy is typically greater than δ34SCAS measured from the same samples. We propose that CAS and pyrite were derived from two isotopically distinct reservoirs in a chemically stratified basin. Chapter 4 studies δ13C, δ18O, δ34SCAS, and δ34Spy of the Zhoujieshan cap carbonate that overlies the Ediacaran Hongtiegou glaciation. The Zhoujieshan cap dolostone shows positive δ13C values (0 â 1.7â °). δ34SCAS shows rapid stratigraphic variations from +13.9 to +24.1â °, probably due to relatively low oceanic sulfate concentrations. δ34Spy shows a steady stratigraphic trend. Thus, the δ34SCAS and δ34Spy trends are decoupled from each other. The decoupling of δ34SCAS and δ34Spy trends suggests that CAS and pyrite were derived from different sulfur pools, which were probably due to the postglacial basin stratification. / Ph. D.

Grupo Corumbá representa um dos mais completos registros sedimentares do Ediacarano na América do Sul, com afloramentos de rochas siliciclásticas e carbonáticas ao longo da Faixa Paraguai Sul. Estas rochas contêm um rico conteúdo fossilífero, com ocorrências dos primeiros organismos com estruturas biomineralizadas (Cloudina sp). Este trabalho apresenta o estudo faciológico e quimioestratigráfico da Formação Tamengo, Grupo Corumbá na mina Laginha, sucessão carbonática de 130 metros de espessura, em contato erosivo na base com brechas calcárias e no topo com os pelitos da Formação Guaicurus. Para a Formação Tamengo foram descritas 4 fácies sedimentares: brecha calcária intraformacional (F1), grainstone oolítico (F2), packstone/grainstone oolítico (F3) e ritmito (F4), as quais representam a evolução de uma rampa interna-média com geração de barras oolíticas, submetida à ação de correntes e ondas de alta energia. Os dados geoquímicos e isotópicos dos carbonatos mostram as condições geoquímicas dessa rampa carbonática depositada em ambiente marinho de águas rasas. Análises isotópicas de carbono e oxigênio foram realizadas em 130 amostras de rocha, coletadas a cada um metro. Com base nos teores de Rb e Sr determinados por FRX, as 10 amostras com altas concentrações de Sr foram selecionadas para análise isotópica de Sr e geoquímica elementar. Na base da sucessão, os carbonatos oolíticos mostram valores de ?13C (V-PDB) de cerca de -3,5 ?, aumentando para +6,0 ? nos primeiros 70 metros basais da sequência. O aumento nos valores de ?13C é interpretado como resultado do aumento da taxa de matéria orgânica soterrada. Acima desse intervalo, observa-se uma tendência homogênea dos valores ?13C, oscilando entre 1,7 e 3,4 ?. A estabilidade nestes valores positivos pode estar relacionada ao equilíbrio entre a taxa de matéria orgânica soterrada e a reciclagem do carbono pela degradação da matéria orgânica. Os valores de ?18O (V-PDB) são todos negativos e mostram uma tendência progressiva em toda a seção, de -1,8 na base a -9,3 ? na parte superior. Os valores de ?18O provavelmente não refletem as composições isotópicas primárias devido à alteração pós-deposicional. As razões 87Sr/86Sr variaram entre 0,7085 e 0,7089, as quais são concordantes com a evolução global para o final do Ediacarano. Os resultados obtidos permitem inferir que estas razões representam a composição isotópica da água do mar na época da deposição. A presente investigação contribui para o conhecimento das condições geoquímicas presentes nos ambientes marinhos rasos da rampa carbonática onde as rochas da Formação Tamengo foram depositadas e suas implicações no desenvolvimento das comunidades biológicas que evoluíram no final do Ediacariano. / The Corumbá Group represents one of the most complete sedimentary records of the Ediacaran in South America, with outcrops of siliciclastic and carbonate rocks along the southern Paraguay Belt. These rocks contain a rich fossiliferous content, with occurrences of the first organisms with biomineralized structures (Cloudina sp). This work presents the faciologic and chemostratigraphic study of the Tamengo Formation, Corumbá Group, at the Laginha mine, a 130 - m thick carbonate succession, in erosive contact at the base with carbonate breccias and at the top with pelites of the Guaicurus Formation. Four sedimentary facies have been described in the Tamengo Formation: intraformational breccia (F1) oolitic grainstone (F2) oolitic packstone/grainstone (F3) and rhythmites (F4), which represent the evolution of an inner-mid ramp with oolitic bars generation, subjected to the action of currents and waves of high energy. Elementar and isotope geochemistry of carbonates show the chemical conditions in the shallow-water marine environments of this carbonatic ramp. Carbon and oxygen isotopic analysis were performed on 130 calcareous samples, collected each meter. Based on the Rb and Sr contents determined by XRF, ten samples with high Sr concentrations were selected for Sr isotope and elemental geochemical analysis. The ?13C (V-PDB) values start with -3.5 ? at the base of oolitic carbonates, increasing to +6.0 ? in the first 70 meters at the base of the sequence. The increase in ?13C values is preliminarily interpreted as a result of the increase in the organic matter buried. Above this interval, a homogeneous trend is observed in the ?13C values, oscillating between 1.7 and 3.4 ?. The stability of these positive values can be related to a balance between the buried organic matter and carbon recycling by organic matter degradation. The ?18O (V-PDB) values are all negative and show a progressive trend throughout the section, from -1.8 at the base to -9.3 ? at the top. This trend of the ?18O values probably do not reflect the primary isotopic composition due to post-depositional alteration. 87Sr/86Sr ratios ranged between 0.7085 and 0.7089, which are in accordance with the global Sr isotope evolution of the late Ediacaran seawater. The obtained results allow us to infer that these ratios represent the isotopic composition of seawater at the time of deposition. The present study contributes to the knowledge of the geochemical conditions of the shallow marine environments of the Tamengo Formation, which has implications in the development of the biological communities that evolved at the end of the Ediacaran.

Anomalias biogeoquímicas expressivas têm sido reconhecidas em rochas marinhas neoproterozoicas depositadas em todos os continentes, não havendo similares ao longo do Fanerozoico. O interesse nesta Era aumentou nos últimos anos, especialmente em relação ao Ediacarano, período que precede a grande Explosão de Vida Cambriana e que abriga os primeiros organismos macroscópicos, conhecidos como Fauna de Ediacara. Assim, o entendimento das condições paleoambientais e paleoclimáticas, bem como o estabelecimento da cronologia dos eventos, é fundamental no entendimento da evolução da biota no planeta durante este período. As rochas da Faixa Paraguai Norte, na região de estudo, registram a ocorrência de duas glaciações, uma criogeniana e outra ediacarana (formações Puga e Serra Azul), separadas por uma espessa plataforma carbonática (Grupo Araras), que registra anomalias biogeoquímicas na água do mar ediacarano. Estas rochas foram depositadas na margem sudeste do Craton Amazônico, no intervalo de tempo entre a quebra do paleocontinente Rodínia e a colagem do Gondwana. O presente trabalho é apresentado na forma de artigos e apresenta estudos de: i) quimioestratigrafia isotópica (C, O, S e Sr) de detalhe nos carbonatos do Grupo Araras e da Formação Serra Azul; ii) proveniência (Sm-Nd) das rochas terrígenas das formações Puga e Serra Azul, bem como da base da Formação Raizama; e iii) geocronologia (Pb-Pb em carbonatos e K-Ar em clastos vulcânicos) da Formação Serra Azul. Os valores de \'delta\'\'POT.13 C\' evidenciaram duas anomalias negativas (ca. - 6%o) pósglaciais e um gradiente de até 2,5%o ao longo da bacia, no período interglacial. As razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 Sr\' (entre 0.7074 e 0.7087) mostraram uma evolução coerente com a esperada para o oceano ediacarano. Os valores de \'delta\'\'POT.34 S\' obtidos nos sulfatos-traços dos carbonatos variaram de 22 a 61, enquanto que nas piritas variaram de 11 a 43%o, sendo os mais pesados já registrados no tempo geológico (acima de 48%o e 30%o, respectivamente). As idades modelo (\'T IND.DM\') Sm-Nd obtidas em rochas terrígenas das formações Puga, Serra Azul e Raizama encontram-se entre 1,6 e 2,2 Ga, mostrando contribuição variável, ao longo da seção, com predomínio de fontes localizadas a norte e a leste da bacia precursora da Faixa Paraguai. As idades K-Ar obtidas em clastos vulcânicos recuperados da Formação Serra Azul variaram de 730 a 1167 Ma, evidenciando uma fonte jovem, distinta do esperado para o Cráton Amazônico. A idade isocrônica Pb-Pb de 596 ± 26 Ma determinada em carbonatos da Formação Serra Azul corrobora sua correlação com a Glaciação Gaskiers, datada em 580 Ma. / Expressive biogeochemical anomalies have been recognized in Neoproterozoic marine rocks deposited worldwide, with no similar record throughout the Phanerozoic. The interest in this Era have been increased, especially on the Ediacaran time, the period that precedes the great CambrianLife Explosion, and houses the first macroscopic organisms, which are known as the Ediacaran Fauna. Thus, the understanding of paleoclimatic and paleoenvironmental conditions, associated with the establishment of the chronology of the events is crucial in the understanding the evolution of biota on the planet during this period. The rocks of northern Paraguay Belt in the study area record the occurrence of two glaciations, where one is Cryogenian and another is Ediacaran (Puga and Serra Azul formations). These glacial deposits are separated by a thick carbonate platform (Araras Group), which records biogeochemical anomalies in the Ediacaran seawater. These rocks were deposited in the southeastern margin of the Amazonian Craton, in the time interval between the breakup of the Rodinia Paleocontinent and the assemblage of the Gondwana. This work is composed by five articles, whose study scopes are: i) detailed isotope chemostratigraphy (C, O, S and Sr) in carbonates from the Araras Group and the Serra Azul Formation; ii) provenance (Sm-Nd) of the siliclastic rocks from the Puga and the Serra Azul Formations and the base of the Raizama Formation; and iii) geochronology (Pb-Pb in carbonate and K-Ar in volcanic clasts) from the Serra Azul Formation. The \'delta\'\'POT.13 C\' values showed two post-glacial negative anomalies (ca. - 6%o) and a gradient of up to 2.5%o along the basin, during interglacial period. The obtained \'ANTPOT.87 Sr\'/\'ANTPOT.86 Sr\' ratios (between 0.7074 and 0.7087) showed a consistent trend with that expected for the Ediacaran sea water. The trace sulfate extracted from obtained carbonates yielded \'delta\'\'POT.34 S\' values from 22 to 61%o, whereas the pyrites ranged between 11 and 43%o. These \'delta\'\'POT.34 S\' values are the heaviest ever recorded in geologic time (above 48 and 30, respectively). The Sm-Nd model ages (\'T IND.DM\') obtained from siliciclastic rocks from Puga, Serra Azul and Raizama formations range from 1.6 to 2.2 Ga, and indicate a variable contribution along the section, with predominant sources coming from areas at north and east of the precursor basin. Recovered volcanic clasts from the Serra Azul Formation yielded K-Ar ages between 730 and 1167 Ma, revealing a non expected young source for areas on the Amazon Craton. The Pb-Pb isochron age of 596 ± 26 Ma was determined in carbonates from the Serra Azul Formation and corroborates its correlation with Gaskiers Glaciation which was dated at 580 Ma.

abstract: There is a growing body of evidence that the evolving redox structure of the oceans has been an important influence on the evolutionary trajectory of animals. However, current understanding of connections between marine redox conditions and marine extinctions and recoveries is hampered by limited detailed knowledge of the timing, duration, and extent of marine redox changes. The recent development of U isotopes (δ238U) in carbonates as a global ocean redox proxy has provided new insight into this problem. Reliable application and interpretation of the δ238U paleoproxy in geological records requires a thorough understanding of the reliability of δ238U recorded by bulk carbonate sediments. In this dissertation, I evaluate the robustness of δ238U paleoproxy by examining δ238U variations in marine carbonates across Permian-Triassic boundary (PTB) sections from different paleogeographic locations. Close agreement of δ238U profiles from coeval carbonate sections thousands of kilometers apart, in different ocean basins, and with different diagenetic histories, strongly suggests that bulk carbonate sediments can reliably preserve primary marine δ238U signals, validating the carbonate U-isotope proxy for global-ocean redox analysis. To improve understanding of the role of marine redox in shaping the evolutionary trajectory of animals, high-resolution δ238U records were generated across several key evolutionary periods, including the Ediacaran-to-Early Cambrian Explosion of complex life (635-541 Ma) and the delayed Early Triassic Earth system recovery from the PTB extinction (252-246 Ma). Based on U isotope variations in the Ediacaran-to-the Early Cambrian ocean, the initial diversification of the Ediacara biota immediately postdates an episode of pervasive ocean oxygenation across the Shuram event. The subsequent decline and extinction of the Ediacara biota is coincident with an episode of extensive anoxic conditions during the latest Ediacaran Period. These findings suggest that global marine redox changes drove the rise and fall of the Ediacara biota. Based on U isotope variations, the Early Triassic ocean was characterized by multiple episodes of extensive marine anoxia. By comparing the high-resolution δ238U record with the sub-stage ammonoid extinction rate curve, it appears that multiple oscillations in marine anoxia modulated the recovery of marine ecosystems following the latest Permian mass extinction. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2018

The first Isaac carbonate (FIC) is a mixed siliciclastic-carbonate base-of-slope succession in the Neoproterozoic Windermere Supergroup (WSG). Outstanding outcrop exposure at three study areas provided an excellent opportunity to observe the stratigraphic and isotopic evolution of an ancient deepwater mixed turbidite system. Based on lithological and stratal dimensions, the FIC can be subdivided into lower and upper parts suggesting temporal changes in patterns of sediment transport and deposition. δ13Ccarb also changes from -5.2‰ at the base of the FIC to 2.5‰ in the middle and then decreases to -6.3‰ at the top. Notably, the δ13Ccarb of primary cement in FIC strata is substantially more positive than most other Neoproterozoic deep-marine sections, suggesting the retention of their original shallow-marine isotopic signature. Nevertheless, this trend potentially correlates with the EN2 excursion in China and therefore the Gaskiers glaciation (~580 Ma), although better age control of WSG is needed to corroborate this correlation.

Anomalias biogeoquímicas expressivas têm sido reconhecidas em rochas marinhas neoproterozoicas depositadas em todos os continentes, não havendo similares ao longo do Fanerozoico. O interesse nesta Era aumentou nos últimos anos, especialmente em relação ao Ediacarano, período que precede a grande Explosão de Vida Cambriana e que abriga os primeiros organismos macroscópicos, conhecidos como Fauna de Ediacara. Assim, o entendimento das condições paleoambientais e paleoclimáticas, bem como o estabelecimento da cronologia dos eventos, é fundamental no entendimento da evolução da biota no planeta durante este período. As rochas da Faixa Paraguai Norte, na região de estudo, registram a ocorrência de duas glaciações, uma criogeniana e outra ediacarana (formações Puga e Serra Azul), separadas por uma espessa plataforma carbonática (Grupo Araras), que registra anomalias biogeoquímicas na água do mar ediacarano. Estas rochas foram depositadas na margem sudeste do Craton Amazônico, no intervalo de tempo entre a quebra do paleocontinente Rodínia e a colagem do Gondwana. O presente trabalho é apresentado na forma de artigos e apresenta estudos de: i) quimioestratigrafia isotópica (C, O, S e Sr) de detalhe nos carbonatos do Grupo Araras e da Formação Serra Azul; ii) proveniência (Sm-Nd) das rochas terrígenas das formações Puga e Serra Azul, bem como da base da Formação Raizama; e iii) geocronologia (Pb-Pb em carbonatos e K-Ar em clastos vulcânicos) da Formação Serra Azul. Os valores de \'delta\'\'POT.13 C\' evidenciaram duas anomalias negativas (ca. - 6%o) pósglaciais e um gradiente de até 2,5%o ao longo da bacia, no período interglacial. As razões \'ANTPOT.87 Sr\'/\'ANTPOT.86 Sr\' (entre 0.7074 e 0.7087) mostraram uma evolução coerente com a esperada para o oceano ediacarano. Os valores de \'delta\'\'POT.34 S\' obtidos nos sulfatos-traços dos carbonatos variaram de 22 a 61, enquanto que nas piritas variaram de 11 a 43%o, sendo os mais pesados já registrados no tempo geológico (acima de 48%o e 30%o, respectivamente). As idades modelo (\'T IND.DM\') Sm-Nd obtidas em rochas terrígenas das formações Puga, Serra Azul e Raizama encontram-se entre 1,6 e 2,2 Ga, mostrando contribuição variável, ao longo da seção, com predomínio de fontes localizadas a norte e a leste da bacia precursora da Faixa Paraguai. As idades K-Ar obtidas em clastos vulcânicos recuperados da Formação Serra Azul variaram de 730 a 1167 Ma, evidenciando uma fonte jovem, distinta do esperado para o Cráton Amazônico. A idade isocrônica Pb-Pb de 596 ± 26 Ma determinada em carbonatos da Formação Serra Azul corrobora sua correlação com a Glaciação Gaskiers, datada em 580 Ma. / Expressive biogeochemical anomalies have been recognized in Neoproterozoic marine rocks deposited worldwide, with no similar record throughout the Phanerozoic. The interest in this Era have been increased, especially on the Ediacaran time, the period that precedes the great CambrianLife Explosion, and houses the first macroscopic organisms, which are known as the Ediacaran Fauna. Thus, the understanding of paleoclimatic and paleoenvironmental conditions, associated with the establishment of the chronology of the events is crucial in the understanding the evolution of biota on the planet during this period. The rocks of northern Paraguay Belt in the study area record the occurrence of two glaciations, where one is Cryogenian and another is Ediacaran (Puga and Serra Azul formations). These glacial deposits are separated by a thick carbonate platform (Araras Group), which records biogeochemical anomalies in the Ediacaran seawater. These rocks were deposited in the southeastern margin of the Amazonian Craton, in the time interval between the breakup of the Rodinia Paleocontinent and the assemblage of the Gondwana. This work is composed by five articles, whose study scopes are: i) detailed isotope chemostratigraphy (C, O, S and Sr) in carbonates from the Araras Group and the Serra Azul Formation; ii) provenance (Sm-Nd) of the siliclastic rocks from the Puga and the Serra Azul Formations and the base of the Raizama Formation; and iii) geochronology (Pb-Pb in carbonate and K-Ar in volcanic clasts) from the Serra Azul Formation. The \'delta\'\'POT.13 C\' values showed two post-glacial negative anomalies (ca. - 6%o) and a gradient of up to 2.5%o along the basin, during interglacial period. The obtained \'ANTPOT.87 Sr\'/\'ANTPOT.86 Sr\' ratios (between 0.7074 and 0.7087) showed a consistent trend with that expected for the Ediacaran sea water. The trace sulfate extracted from obtained carbonates yielded \'delta\'\'POT.34 S\' values from 22 to 61%o, whereas the pyrites ranged between 11 and 43%o. These \'delta\'\'POT.34 S\' values are the heaviest ever recorded in geologic time (above 48 and 30, respectively). The Sm-Nd model ages (\'T IND.DM\') obtained from siliciclastic rocks from Puga, Serra Azul and Raizama formations range from 1.6 to 2.2 Ga, and indicate a variable contribution along the section, with predominant sources coming from areas at north and east of the precursor basin. Recovered volcanic clasts from the Serra Azul Formation yielded K-Ar ages between 730 and 1167 Ma, revealing a non expected young source for areas on the Amazon Craton. The Pb-Pb isochron age of 596 ± 26 Ma was determined in carbonates from the Serra Azul Formation and corroborates its correlation with Gaskiers Glaciation which was dated at 580 Ma.

Hiemalora is a genus residing within the Ediacaran biota. There are just two species of Hiemalora; H. stellaris and H. pleiomorphus. Despite there being only being two species within this genus, there is a degree of morphological variability within each species which is highlighted by the description of specimens around the world. The distribution of Hiemalora is global with specimens observed in Newfoundland, England, the White Sea (Russia), Siberia, Australia and arctic Norway. There has been a great deal of evolution in the interpretation of Hiemalora since the original description of H. stellaris in 1980. This genus was first interpreted as a hydrozoan with a central polyp with radiating tentacles (Fedonkin. 1981). It is now thought to be associated with rangeomorphs as a holdfast-type basal attachment structure. It is most closely linked to the frondose taxon Primocandelabrum which is abundant in Mistaken Point, Newfoundland and Charnwood Forest, England.The Hiemalora fossils in this study are sampled from the Indreelva member on the Digermulen Peninsula, Finnmark, Norway during fieldwork in both 2015 and 2018 at two close although separate localities. The most abundant species in this study is H. stellaris which makes up the majority of the 9 samples. There is also the potential inclusion of a H. pleiomorphus specimen, which features a distinctly different morphology to the other Hiemalora samples. One specimen has been identified with what is possibly a Primocandelabrum frond attachment. It is almost certainly a rangeomorph although the affinity is up for debate. One of the main aims for this study is to, as accurately as possible, determine the taxonomic affinity for all the specimens. This is subsequently an aim to better understand the biota inhabiting the Ediacaran seafloor in Digermulen Peninsula and the palaeoenvironment. This study is the first incorporating Hiemalora concerning material from the Digermulen Peninsula since the work done since Farmer et al. in 1992 and the first study in this area solely focused on the genus. Due to this, the study is allowing for the comparison between modern interpretations of Hiemalora from other Ediacaran locations around the world. Due to the Digermulen Peninsula residing on Baltica during the Ediacaran, comparisons to Avalonian assemblages such as in Newfoundland and England may highlight polarising features or many similarities. / Hiemalora är ett släktskap av skivformad organism som levde under Ediacaraperioden. Ediacara är den sista perioden under Neoproterozoicum och varade från 631Ma till 541Ma. Fossil av Hiemalora är globalt distribuerade, med exemplar från Ryssland, England, Kanada, Australien och Norge. Hiemalora-exemplaren i denna studie hittades på Digermulen-halvön i Finnmark, Norge. Det har funnits många olika tolkningar av Hiemalora kring dess livsstil, utseende och dess affinitet inom fylogenien eftersom den först beskrevs 1980. Den enkla uppbyggnaden hos fossilen, med bara en central skiva och "tentakelliknande" strålar som härrör från det i ett plan lämnar mycket för tolkning. Hiemalora är relativt sällsynt i jämförelse med andra skivformade fossil. Andra discoidala Ediacarafossil som Aspidella är mycket vanligare. Det finns två arter av Hiemalora som har beskrivits. Dessa är H. stellaris och H. pleiomorphus. Det finns subtila morfologiska skillnader mellan dessa arter. Skillnader mellan dessa arter inkluderar parallella ribbliknande strukturer på ytan av den centrala skivan av H. pleiomorphus och tätt packade strålar. Den centrala skivan i H. pleiomorphus är också proportionellt större i jämförelse med dess centrala skiva. H. stellaris har associerats med fronds. Fronds är en förgreningsstruktur som är orienterad vertikalt i vattenkolumnen. Dessa strukturer är associerade med olika skivliknande organismer och kan ha en stor morfologisk variation. Den frond som är associerad med H. stellaris är Primocandelabrum. Denna frond ses vid H. stellaris fossil i Newfoundland, Kanada. En frond som är tveksamt identifierad som Primocandelabrum ses vid en av Hiemalora-exemplaren i denna studie. Betydelsen av detta skulle vara att det är det första Hiemalora-exemplaret utanför Newfoundland och Charnwood Forest, England som bevaras med en Primocandelabrum frond. Det finns nuvarande idéer att Primocandelabrum och H. stellaris kan vara samma organism fast med olika delar bevarade. Faktumet att båda delarna är bevarade på Digermulen halvön kan ge mer inblick i detta. Sju av Hiemalora-exemplaren i denna studie är H. stellaris, medan en art möjligen är H. pleiomorphus. Provet med fronden är sannolikt H. stellaris, men på grund av att den är dåligt bevarad runt centralskivan är dess affinitet inte säker. En dålig bevarandekvalitet hos många exemplar i studien gjorde det svårt att identifiera den. Bevarandet ger dock en inblick i miljön som Hiemalora bodde i och under vilka förhållanden den dog. Många platser runt om i världen har exceptionellt bevarade fossil som kan ha varit möjligt på grund av en händelse där alla blev bevarade samtidigt, likt de vulkaniska askadepositionerna i Newfoundland. Detta var inte fallet i Digermulen-halvön, där organismer sannolikt inte begravdes omedelbart efter döden.