Dissertations / Theses: 'Stromatolites'

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Feldmann, Markus. "Controls on stromatolite formation : a comparative study of modern stromatolites from the Bahamas with Messinian examples from Southeast Spain /." [S.l.] : [s.n.], 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11119.

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Petroff, Alexander Peter Phillips. "Streams, stromatolites and the geometry of growth." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68996.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 148-159).
This collection of papers is about recognizing common geometric features in the dynamics shaping diverse phenomena in the natural world. In particular, we focus on two systems which grow in response to a diffusive flux. The first system is a microbial mat which overlays a layer of precipitated mineral. The microbial mat grows in response to the diffusion of nutrients while the mineral layer grows in response to the precipitation of dissolved ions which diffuse through the microbial mat. The second system is a network of streams that are fed by groundwater. In this case, groundwater flows through the aquifer and into the streams along the gradient of the pressure field, which, at equilibrium, diffuses through the aquifer. Here we show how a quantitative understanding of the shapes and scales of these two systems can be gained from physical and mathematical reasoning with few assumptions. We begin by considering the physical dimensions of systems shaped by diffusion. Guided by field observation and laboratory experiments of microbial mats, we identify two time scales important to the growth of these mats. We show how these processes shape the mat over different length scales and how these length scales are recognizable in the geometry of the mat. Next, we consider the shape of an interface growing in response to a diffusive flux. In microbial mats and streams, resources are focused toward regions of high curvature. We find that curvature-driven growth accurately predicts the shape of both fossilized microbial mats called stromatolites and the the landscape around a spring. Finally, we consider the geometric forms that arise when competition is mediated by diffusion. In particular, we show that when a growing stream bifurcates, competition between the nascent streams cause them to grow apart at an equilibrium angle of [alpha] = 2[pi]/5. The measured bifurcation angles of streams in a kilometer-scale network are in close agreement with this prediction.
by Alexander Peter Phillips Petroff.
Ph.D.

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Davis, Burton S. "Stromatolites in the upper lacustrine unit of the Paleocene Hanna Formation, Hanna Basin, south-central Wyoming." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1136088711&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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Jabro, Nicholas Berman. "Microcosm studies of nutrient cycling in Bahamian stromatolites." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8594.

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Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Casanova, Joël. "Les Stromatolites continentaux paléo-écologie, paléohydrologie, paléoclimatologie, application au Rift Gregory." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375965168.

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De, Wever Alexis. "Étude de la biominéralisation de carbonates intracellulaires et de silicates de magnésium hydratés dans des environnements lacustres alcalins." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS480.pdf.

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Les stromatolites sont des roches organo-sédimentaires laminées composées de carbonates de Ca et/ou Mg mais également de silicates de Mg dans certains cas. Les processus impliqués dans leur formation restent encore mal compris. L’objectif central de cette thèse est de mieux comprendre les processus géochimiques et géomicrobiologiques permettant de favoriser ou au contraire de défavoriser la formation des carbonates et silicates de magnésium dans les environnements lacustres alcalins mexicains. Deux axes principaux ont été développés. Le premier axe s’est focalisé sur les analyses de souches formant des carbonates de calcium amorphes (ACC) intracellulaire (ACC+) ou non. Une grande diversité de souches de cyanobactéries a été analysée pour leur capacité à incorporer le Ca. De plus, l’impact des alcalino-terreux sur la croissance de certaines de ces souches a été déterminé. A partir de cette étude, nous avons mis en évidence que les souches de cyanobactérie ACC+ incorporent plus de Ca que les autres et qu’elles le stockent principalement dans les inclusions d’ACC et dans les polyphosphates (polyP). De plus, nous avons déterminé que les souches ACC+ ont relativement plus besoin de Ca pour leur croissance et certaines d’entre elles sont capables de substituer le Ca par du Sr et Ba. Nous proposons que les inclusions d’ACC 1) peuvent servir de ballasts, 2) peuvent tamponner le pH intracellulaire et équilibrer la formation d'hydroxyde par conversion de HCO3 en CO2 lors de la fixation du carbone et 3) alternativement, ils peuvent servir de forme de stockage de carbone inorganique disponible pour les cellules sur des périodes limitées en C. De plus, les polyP pourraient être impliqués dans le stockage de Ca. Plus largement, les cyanobactéries ACC+ pourraient favoriser la dissolution de carbonate de Ca et par extension celle des stromatolites. Le second axe s’est intéressé à l’étude de la formation de silicates de magnésium dans les sédiments et mésocosmes analogues de 3 lacs alcalins mexicains mais également par des expériences de biominéralisation. Les analyses minéralogiques et chimiques des silicates de magnésium ont été couplées aux caractérisations géochimiques des solutions. L’étude des sédiments a montré la formation de deux smectites, l’une pauvre et l’autre riche en Al et également de smectite ferrugineuse ou sans forte teneur en Fe. Plusieurs interprétations ont été proposées quant à leur formation : 1) la dissolution conjointe d’hydromagnésite et des frustules de silice biogénique, 2) elle est héritée de la colonne d’eau, 3) est liée à l’altération des feldspaths dans les sédiments et 4) à la biominéralisation dans la colonne d’eau. Il a également été montré qu’une souche de cyanobactéries est capable d’induire la précipitation de silicates de magnésium en milieu non tamponné. Dans les mésocosme des lacs alcalins, la formation de silicate de Mg serait directement liée à la composition minéralogique des microbialites, et possiblement des diatomées permettant l’apport de Si dans la solution et localement dans le biofilm, et est biologiquement influencée par les EPS des communautés microbiennes
Stromatolites are laminated organo-sedimentary rocks composed of Ca and/or Mg carbonates but also Mg-silicates in some cases. The processes involved in their formation are still poorly understood. The main goal of this thesis was to better understand the geochemical and geomicrobiological processes that favor the formation or dissolution of carbonates and Mg-silicates in Mexican alkaline lacustrine environments. Two main axes have been developed. The first axis focused on the study of 52 cyanobacterial strains, some forming ACC intracellular, others not forming ACC. The strains were analyzed for their ability to incorporate Ca. The impact of alkaline earth elements on the growth of some of the strains was determined. In this study we have shown that ACC+ cyanobacterial strains incorporate more Ca than others and they store this Ca strongly in ACC and in polyP. In addition, we determined that ACC+ strains need more Ca for their growth and some of them are capable to substitute Ca by Sr and Ba for this purpose. We propose that ACC inclusions 1) can serve as ballasts, 2) can buffer intracellular pH and balance the formation of HCO3 conversion hydroxide to CO2 during carbon fixation and 3) available inorganic carbon storage for carbon dioxide. In addition, polyP could be involved in Ca storage. More broadly, ACC+ cyanobacteria have contributed to the dissolution of calcium carbonate and by extension stromatolites. The second axis focused on the study of Mg-silicate formation in sediments and mesocosms of 3 Mexican alkaline lakes but also in laboratory experiments. Mineralogical and chemical analyzes of magnesium silicates have been coupled with geochemical characterization of the solutions. The study of sediments showed the formation of an Al-low and an Al-rich stevensite-like phase and of ferrous or non-ferrous saponite-like. Several interpretations have been proposed regarding their formation: 1) dissolution of hydromagnesite and biogenic silica frustules, 2) it is inherited from the water column, 3) it is related to the alteration of feldspaths within sediments and 4) biomineralization in the water column. It has also been shown that a cyanobacterial strain was able to induce precipitation of magnesium silicates in an unbuffered medium. Mg-silicate formation in mesocosms from alkaline lakes is thought to be directly related to the mineralogical composition of microbialites, and possibly diatoms that allow Si to be introduced into the solution and locally into the biofilm and is biologically influenced by microbial community EPS

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Guirdham, Claire. "Regional stratigraphy, lithofacies, diagenesis and dolomitisation of microbial carbonates in the Lower Carbonifereous, West Lothian Oil-Shale Formation." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266732.

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The Dinantian West Lothian Oil-Shale Formation of the Midland Valley, Scotland, is a laterally variable lacustrine sequence, deposited in an overall humid climatic period. The sequence comprises non-marine limestones, dolostones, oil-shales, mudrocks and deltaic sandstones. Thin marine bands and the thick freshwater Burdiehouse Limestone are the most reliable stratigraphic markers. Eight individual outcrops of microbial carbonatesa, ll stratigraphically close to the Burdiehouse Limestone, are correlatable, and therefore important in helping to clarify the Asbian stratigraphy of the eastern Midland Valley of Scotland. The microbial carbonates were deposited in varied shallow lake settings. Lake waters had a long residence time, suggested by fairly positive stable carbon and oxygen isotope ratios. Petrography and geochemistry suggest the primary carbonate was high-Mg calcite. Isotopic variations are mainly controlled by depositional water depth, diagenetic fluid temperaturesl,o calised magmatica ctivity and in-situ organicm atterd ecay. A regional dolornitisation event affected the lithologies, with high Fe" and Mg2+ concentrations suggesting early diagenetic dolomitisation under phreatic conditions. High Sr dolomite suggestst hat the lake and / or regional groundwaters were Sr enriched. Both the Sr ions and the Mg ions for dolomitisation were probably derived from chemically-enriched, seaward flowing groundwaters, that originated on a westerly situated volcanic plateau. The microbial carbonates represent regional and localised regressive sequences, lake, and in volcanically-isolated depositional sub-basins. The carbonates probably correspond to a regionally-significant period of aridity within the Asbian of south-east Scotland, similar to fluctuating seasonal semi-arid and humid conditions identified in the Dinantian of England and Wales.

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Evans, Alexander Joseph. "Characteristics of cone-forming cyanobacteria and implications for the origin of conical stromatolites." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84913.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-57).
Dating back to 3.5 Gya, stromatolites, which are composed of laminated and lithified carbonate rock, may contain the earliest records of phototaxis, photosynthesis, and oxygenation of the environment. The reconstruction of the co-evolution of biology and the environment using stromatolites depends on the ability to recognize macroscopic shapes that arise uniquely as a consequence of microbial processes. Our investigation aims to understand the biological factors in the formation of conical structures and stromatolites. To elucidate the role of the cyanobacteria, we enrich cyanobacteria from modern hot-spring communities of cone-forming microbes and subsequently test how the formation of conical structures depends on individual strains of the community. In our analysis, we augment morphological identification by genomic analyses of the 16S ribosomal DNA. Through a combination of mixing isolated heterotrophic bacteria and enriched filamentous cyanobacteria communities, we find that heterotrophic bacteria are a determinative factor in the formation and morphology of conical structures. Further, our experiments show the mere presence of a thin, filamentous cone-forming cyanobacteria phenotype is not a sufficient condition for cone formation.
by Alexander Joseph Evans.
S.M.

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Myers, Elise McKenna. "Complex lipids in microbial mats and stromatolites of Hamelin Pool, Shark Bay, Australia." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/114126.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 44-50).
Stromatolites, columnar rock-like structures, are potentially some of the oldest, microbially mediated fossils visible in the rock record; if biogenesis is able to be confirmed for these ancient stromatolites, some being greater than 3 billion years old, these ancient stromatolites could be used to demonstrate the microbial community assemblages throughout ancient time. Hamelin Pool, Shark Bay, Australia is an ideal field site for this task, as stromtolites and modern microbial mats coexist and the microbial mats have been shown to contribute to the formation of the stromatolites. Comprehensive lipid biomarker profiles were determined in this study for non-lithified smooth, pustular, and colloform microbial mats, as well as for smooth and colloform stromatolites. Intact polar lipids, glycerol dialkyl glycerol tetraethers, and bacteriohopanepolyols were analyzed via liquid chromatography-mass spectrometry (LC-MS) coupled to a Quadropole Time-of-Flight (QTOF) mass spectrometer, while the previously studied fatty acids (Allen et al., 2010) were analyzed using gas chromatography-mass spectrometry (GC-MS) to prove consistent signatures. From the lipid profiles, sulfate-reducing bacteria and anoxygenic phototrophic bacteria and archaea could be inferred. The presence of the rare 3-methylhopanoids was discovered in a significant portion of the samples, which could add to the characterization of this molecule, which has only been concretely linked to oxygenic conditions for formation. In accordance with Allen et al. in 2010, 2-methyhopanoids were detected, as well as limited signals from higher (vascular) plants. While the lipid profiles for all sediment types were similar, there were some differences that are likely attributable to morphological differences. However, the overall similarities suggest microbial communities can be similar between non-lithified microbial mats and stromatolites.
by Elise McKenna Myers.
S.B.

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Osterhout, Jeffrey T. "Diversity of Microfossils and Preservation of Thermally Altered Stromatolites from Anomalous Precambrian Paleoenvironments." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470753351.

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Olden, Liam J. "Mid Phanerozoic stromatolites in the Northern Perth Basin: Understanding their evolution and occurrence." Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/81908.

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Stromatolites from the northern Perth Basin, Western Australia, purported to be associated with the End Permian mass extinction (EPME), were re-examined through several new sites over an expanded 24 km2. New lithological relationships show the stromatolites are intimately associated with a clastic sequence and formed within a fluvio-lacustrine setting. A revised mid to late Permian age is proposed for the stromatolites, disassociated from the EPME. Stromatolite microstructures representing remnant skeletal cyanobacteria are exceptionally preserved throughout.

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Hillman, Colin. "Structure of benthic microbial mat assemblages in Lake Fryxell, Antarctica." Thesis, University of Canterbury. Gateway Antarctica, 2013. http://hdl.handle.net/10092/8737.

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Microbial mats are important components of perennially ice-covered Antarctic lakes in the McMurdo Dry Valleys, where they often comprise the dominant biomass in this cold, shaded environment. These lakes represent some of the most extreme lacustrine environments on Earth, including a persistent ice-cover, stable, stratified water columns, with strong salinity related density gradients. In these low-disturbance environments, the microbial consortia develop macroscopic emergent structures such as pinnacles and ridges. Such structures are speculated to confer advantageous survival traits and have also been found in the Precambrian fossil record as “conophyton” stromatolites – arguably some of the earliest evidence of life – and it has been suggested that a better understanding of the growth dynamics of modern “conophyton” will inform our understanding of what was required for these early fossils to be produced. Despite decades of research, there are few studies of the structural basis of conophyton producing microbial mats in Antarctic lakes. To help address this gap, complex microbial mats along a transect established in Lake Fryxell, one of the McMurdo Dry Valley lakes, were examined; with the aim of documenting the distribution of different types of photosynthetic organisms and mat morphologies along environmental gradients such as light, conductivity, oxygen concentration and depth. Microbial mat samples were taken along the transect and analysed in New Zealand using confocal laser scanning microscopy, along with conventional pigment extraction techniques. Correlations between mat morphology, pigment content and lake properties were found. The appearance of bacteriochlorophylls, characteristic of green sulfur bacteria within and below the oxycline confirm a shift from aerobic to anaerobic metabolism that was consistent with mats taking on a prostrate appearance. The cyanobacterial pigment phycoerythrin was only found in the hyperoxic, relatively well lit region of the transect, and was associated with the mats forming a distinctive macroscale morphology with dense fields of cm-scale cuspate pinnacles. Between these, a hypoxic region was characterised by a relatively flat mat within which were many cm-scale pits. Structural investigations were focussed on two distinct morphologies, pinnacle and honeycomb mat. Nearly all photosynthetic organisms were located in the upper 2 mm of both pinnacle and honeycomb mats, mainly comprising diatoms and cyanobacteria. Pinnacle mats were dominated by a narrow cyanobacterium, probably a species of Leptolyngbya, which were mostly oriented vertically, which placed trichomes parallel to the direction of pinnacle extension. The honeycomb mat contained fewer narrow trichomes, rather the bulk of photosynthetic organisms were diatoms from the genera Muellaria, Navicula and Diadesmis, together with broad-trichome cyanobacteria that formed a thin skin on the surface of the mat, though absent from the pits. The type of emergent structure that is formed appears to be related to species composition, and this in turn appears to be related to the growth conditions. A model was developed to explain how species-specific growth mechanisms are involved in emergent structure formation for honeycomb and pinnacle mats.

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Schmidt, David A. "Paleontology and sedimentology of calcifying microbes in the Silurian of the Ohio-Indiana region an expanded role of carbonate-forming microbial communities /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1142964356.

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Fontaneta, Gabriella Talamo. "Dolomitização e fosfogênese na formação bocaina, grupo Corumbá (ediacarano)." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-28022013-102622/.

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Dolomitos são rochas carbonáticas abundantes no registro sedimentar Pré-Cambriano, porém raras no registro Fanerozóico e sua gênese até hoje permanece como um enigma da geologia, conhecido como o \"Problema Dolomito\". As rochas sedimentares fosfáticas são amplamente estudadas por fornecerem dados importantes sobre a evolução sedimentar e condições físico-químicas e biológicas da água do mar durante a sedimentação e a diagênese, além de constituírem os maiores depósitos econômicos de fósforo do mundo. Os dolomitos e fosforitos da Formação Bocaina foram estudados com base na individualização de fácies sedimentares e petrografia, complementado com investigações geoquímicas (elementar e de isótopos de C e O), a fim de discutir os processos envolvidos na gênese destas rochas. As fácies sedimentares da Formação Bocaina, caracterizadas principalmente por grainstonesoolíticos, pisolíticos, e estromatólitos, indicam ambiente de águas rasas, límpidas e agitadas, interpretado como uma laguna, propícia à proliferação microbiana, com conexão restrita ao mar aberto. Estruturas tepeese pseudomorfos de cristais de gipsita sugerem condições evaporíticas para a bacia, com eventos de exposição subaérea dos sedimentos. Os dolomitos da Formação Bocaina são interpretados como secundários, originados da substituição de sedimentos calcíticos na eodiagênese, provavelmentedevido a elevada taxa de evaporação e refluxo das águas oceânicas. Modelos organogênicos para estes dolomitos não são descartados, devido à assinatura isotópica de C ser ligeiramente positiva (\'delta\' POT.13C IND.VPDB\' entre 0,95 e 3,15%o). A fosfogênese é interpretada como um processo eodiagenético, ocorrido em ambiente geoquímico anóxico, corroborado pelas anomalias positivas de Ce. O excesso de matéria orgânica permitiu a formação da apatita, provavelmente bioinduzida, durante eventos de subida do nível do mar, e desta forma, os fosforitos representam um marco estratigráfico para a bacia, como uma superfície condensada. Subseqüentemente, há rebaixamento do nível do mar, registrado nas fácies de fosfarenito e de conglomerado polimítico da base da Formação Tamengo, unidade que se justapõe à Formação Bocaina, marcando o fim do ambiente lagunar restrito e a instalação de uma plataforma francamente marinha.
Dolomites are carbonatic rocks abundant in the Precambrian but rarely found in the Phanerozoic sedimentary record. Their genesis has remained as a long-standing enigma in geology, often called the \"Dolomite Problem\". The phosphatic rocks, which represent the largest economic deposits of phosphorus in the world, have been studied to provide some important data about the sedimentary evolution and physical-chemical and biological condition of seawater during the sedimentation and diagenesis. The dolomites and phosphorites of the Bocaina Formation were studied based on sedimentary facies, petrography, geochemistry and carbon and oxygen isotopes investigations, to understand the process involved in the genesis of both rocks. The sedimentary facies of the Bocaina Formation are characterized by stromatolites, oolitic and pisolitic grainstones, which indicate shallow, clear and agitated water, favorable to microbial growth. The paleoenvironment was interpreted as a lagoon with restrict connection to the sea. Tepees structures and pseudomorphs of gypsum crystals suggest evaporitic condition to this basin, and also show evidences of aridity. The Bocaina Formation\'s dolomites have been interpreted as secondary, from replacement of limestones during eodiagenesis by reflux of oceanic waters. Organogenic models are also consideraded as a process to form these dolomites, based on the positive carbon isotope signature (\'delta\' POT.13 IND.CVPDB\' between 0.95 and 3.15%o). The phosphogenesis has been interpreted as eodiagenetic process occurred in anoxic geochemical environment, due to the excess oforganic matter, mediated by microbial process. The positive Ce anomalies support this interpretation. This process occurs during rising of sea level and the phosphorites represent a stratigraphic mark as a condensed surface. Subsequently, it is observed a sea level lowering, recorded in phospharenite facies and in basal polymict conglomerate of Tamengo Formation, unit which overlies the Bocaina Formation. This lowering event marks the end of the restrict lagoon environment and the installation of a marine platform.

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Romero, Guilherme Raffaeli. "Estromatólitos e estruturas associadas na Capa Carbonática da Formação Mirassol D\'Oeste, Grupo Araras, Faixa Paraguai (Neoproterozoico, MT)." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-08012011-203716/.

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As capas carbonáticas neoproterozóicas revestem-se de grande importância, uma vez que se formaram no meio a mudanças paleoclimáticas e evolutivas singulares, cujas origens e influências na história subsequente do planeta e da vida ainda não foram devidamente esclarecidas. Este trabalho procurou compreender parte desta história através do estudo da sedimentação estromatolítica associada à capa carbonática representada pela Formação Mirassol DOeste (base do Grupo Araras), que se formou há cerca de 635 Ma, imediatemente após a glaciação Marinoana, representada pela Formação Puga. A pesquisa foi realizada na região de Mirassol DOeste, Mato Grosso, na borda sudoeste do Cráton Amazônico junto a Faixa Paraguai. Foram estudadas características meso e microscópicas dos estromatólitos, bem como das feições sedimentológicas associadas (estruturas tubulares, megamarcas onduladas, megapeloides), em afloramento, amostras cortadas e lâminas petrográficas. A dois metros da base da formação, inicia-se uma sucessão de 10 metros de espessura de boundstones microbianos, caracterizados, petrograficamente, por lâminas alternadamente delgadas e espessas, compostas de peloides (restos micritizados de colônias microbianas) com micrita subordinada e fenestras. Constituem estromatólitos lateralmente contínuos e de morfologia simples. Estromatólitos estratiformes ocorrem ao longo de toda a sucessão, com formas dômicas, de dimensões métricas irregularmente espalhadas lateral e verticalmente, até dois ou três metros do topo da sucessão. Estromatólitos muito irregularmente ondulados, comumente assimétricos, com dimensões decímetros predominam a parte superior e estes estão recobertos por grainstones-packstones peloidais dolomíticos, com megapeloides milimétricos, em estratos marcados por megamarcas onduladas formadas por ondas. A sedimentação microbiana cessou na Formação Mirassol DOeste quando o ambiente de plataforma de baixa energia onde se desenvolvia começou a ser assolado pela ação de ondas de hipertempestades, que penetraram a região com o aumento do nível do mar. Estruturas tubulares verticais, de comprimento até decimétrico e diâmetro estreito (<3 cm), preenchidos, via de regra, por doloesparito maciço, perpassam a laminação estromatolítica principalmente das porções mais altas dos domos. Sugere-se que gênese dessas estruturas tenha sido pela percolação de gases e/ou líquidos derivados da decomposição de matéria orgânica nas esteiras microbianas.
Neoproterozoic cap carbonates are of great importance because they formed during a period of singular paleoclimatic and evolutionary changes, whose origin and influences upon subsequent geological and evolutionary history have yet to be unraveled. This dissertation sought to comprehend part of this story through the study of stromatolitic sedimentation associated with the cap carbonate represented by the Mirassol DOeste Formation (base of the Araras Group), deposited about 635 Ma ago, immediately following the Marinoan glaciation, represented by the Puga Formation. This research was carried out at Mirassol DOeste, Mato Grosso, on the southwest border of the Amazon craton next to the Paraguai fold belt. Meso and macroscopic characteristics of stromatolites and associated sedimentological features (tubular structures, megaripples, megapeloids) were studied in outcrop, cut specimens and petrographic thin sections. Two meters above the base of the formation a 10 m-thick succession of dolomitic microbial boundstones begins, characterized throughout by alternating thin and thick laminae made up of peloids (interpreted as the micritized remains of colonial microorganisms), subordinate dolomicrite, and fenestrae. They make up laterally continuous and morphologically simple stromatolites. Stratiform stromatolites occur throughout the succession, with irregularly scattered meter-sized domes till about two to three meters from the top. Above this point, very irregularly undulated, commonly asymmetric, decimeter-sized stromatolites predominate, and these, in turn, are covered by megaripple-marked dolomitic peloidal grainstones-packstones with millimetric megapeloids. Stromatolitic sedimentation ceased in the previously calm platform environment of the Mirassol DOeste Formation when wave action began to rework bottom sediments as extremely intense storms reached the locale with the rise in sea level. Narrow (<3 cm), vertical tubular structures of decimetric length and filled by massive dolosparite cut stromatolitic sediments, principally in the central portions of domal forms. These structures appear to have formed by the percolation of gas and/or liquids derived from the decomposition of organic material in the microbial mats.

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Duque, Johanna Mendez. "Fáceis Carbonáticas da formação Teresina na borba centro-leste da Bacia do Paraná." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-03062015-095646/.

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A Formação Teresina, Neopermiano da Bacia do Paraná, é uma unidade estratigráfica principalmente terrígena, com algumas ocorrências de fácies carbonáticas, sendo depositada durante a última fase regressiva do mar epicontinental da bacia. O ambiente deposicional da Formação Teresina, especialmente no que se refere às suas fácies carbonáticas, ainda é alvo de debate. As fácies carbonáticas da Formação Teresina e fácies evaporíticas associadas ocorrem em toda a formação, mas são mais frequentes no norte do Estado do Paraná e no sul do Estado de São Paulo, na porção superior da unidade. Esta região constitui a área de estudo desta dissertação, que visou interpretar os processos sedimentares básicos, assim como fatores tectônicos e climáticos que influenciaram a formação destes depósitos carbonáticos e evaporíticos. Para isto, foram utilizadas informações de poços e realizados levantamentos detalhados de seções colunares, com coleta de amostras para análises petrográfìcas por microscopia óptica e microscopia eletrônica de varredura (MEV). Foram identificadas e descritas oito fácies carbonáticas e/ou evaporíticas: mudstone com conchas de ostracodes, mudstone peloidal, packstone bioclástico, wackstone bioclástico, boundstone tabular, packstone-grainstone oolítico, brecha de mudstone-chert e chert enterolítico-nodular. O sistema deposicional foi interpretado como uma rampa carbonática com zona interna alta protegida por barreiras arenosas influenciadas por ondas e correntes associadas. Nas partes mais rasas, os períodos áridos e de intensa evaporação e baixo aporte terrígeno provocariam aumento da salinidade e induziria a deposição das fácies evaporíticas de chert enterolítico-nodular e brecha de mudstone-chert. A porção intermediária corresponderia à zona protegida da ação das ondas, com águas rasas e baixa energia. Isto permitiria a deposição de sedimentos finos por decantação, que constituem as fácies mudstone com conchas de ostracodes e wackstone bioclástico. Nesta mesma porção, as condições geoquímicas da água teriam incentivado atividade microbiana, gerando as fácies mudstone peloidal e boundstone tabular. Bandas ricas em dolomita identificadas em fácies de boundstone tabular no norte do Estado do Paraná estariam relacionadas com precipitação mineral induzida por atividade microbiana. Filamentos e nanoestruturas orgânicas observadas podem corresponder a remanescentes fossilizados de extracellular polymeric substance (EPS), usados por bactérias redutoras de sulfato nos processos de precipitação da dolomita-calcita. A ação das ondas causava agitação constante da água, o que originaria a sedimentação das fácies packstone-grainstone oolítico em baixios e das fácies heterolíticas terrígenas em zona distal entre o nível de base das ondas de tempo bom e o nível de base das ondas de tempestade. Mapas de isópacas e de frequência de ocorrência de calcários elaborados a partir da integração dos dados de poços e seções colunares demonstraram aumento da concentração de calcários no flanco norte do Arco de Ponta Grossa (APG). A espessura da formação aumenta em direção ao APG. Em algumas regiões próximas ao APG, as isópacas tornam-se paralelas ao eixo desta estrutura tectônica. Os resultados obtidos sugerem que o Arco de Ponta Grossa atuou como barreira geográfica que restringiu a entrada de águas do oceano vindas do sul e influenciou a deposição das fácies carbonáticas e evaporíticas. A restrição da circulação das águas promoveu o aumento da salinidade na área imediatamente ao norte do arco. Além disso, uma provável zona de convergência de ventos paralela ao Arco de Ponta Grossa e situada ao sul da área de estudo teria dificultado a entrada de massas de ar úmido provenientes do Oceano Panthalassa vindas de sul. Isto favoreceu a instalação de condições áridas na área de estudo. O significado tectônico e climático das fácies carbonáticas e evaporíticas da Formação Teresina podem auxiliar as correlações entre a Bacia do Paraná e bacias na África, tais como as bacias do Huab e Karoo, além de contribuir para reconstruções paleogeográficas do Gondwana no final do Permiano.
The Teresina Formation, Late Permian of the Paraná Basin, is mainly composed of terrigenous sediments, with some occurrences of carbonate and evaporite facies. It corresponds to the upper portion of the last regressive phase of the Paraná Basin epicontinental sea. The depositional system responsible for the carbonate and evaporite facies of the Teresina Formation is still target of discussion. These facies occur in a huge area of the basin, but they have a greater thickness and are more frequent in the north of the Paraná State and in the southern of the São Paulo State, in the upper portion of the formation. This region constitutes the study area of this dissertation in order to interpret the depositional processes as well as the tectonic and climatic factors acting during the formation of these deposits. The study included the interpretation of data from wells, detailed description of columnar sections, with sampling for petrographical analysis under the optical and scanning electron microscopes (SEM). Eight carbonate and/or evaporite facies were identified: mudstone with ostracod shells, peloidal mudstone, bioclastic wackstone, bioclastic packestone, tabular boundstone, oolitic packstone-grainstone, nodular and enterolithic chert and mudstone-chert breccia. The depositional system was interpreted as a carbonate ramp with a protected zone by growth of oolitic sand bars and sediment transport dominated by wave action and associated currents. In the inner regions, arid periods of intense evaporation and low terrigenous input would increase the salinity, causing the deposition of enterolithic and nodular chert and mudstone-chert breccia facies. The intermediate portion corresponds to a lagoon with shallow and low energy waters, allowing the deposition of fine grained sediments recorded in the mudstone with ostracod shells and bioclastic wackstone facies. In the same portion, the hypersaline conditions of the water would have stimulated microbial activity, promoting the deposition of peloidal mudstone and tabular boundstone facies. Dolomite bands identified in the tabular boundstone facies in the north of the Paraná State are enriched in organic matter and they would be associated to mineral precipitation induced by microbial activity. Organic filaments and nanostructures may correspond to fossilized remains of extracellular polymeric substance (EPS), which are used by sulfate-reducing bacteria in the precipitation of dolomite-calcite. The wave action remobilized bottom sediments, causing constant waters agitation. This induced sedimentation of oolitic packstone-grainstone facies in shoals and the terrigenous heterolithic facies between the fair-weather and storm wave bases. Maps of isopachs and frequency of occurrences of limestones show concentration of limestones in the north flank of the Ponta Grossa Arch (PGA). The thickness of the formation increases from south to north towards the PGA. In some regions near the PGA, isopachs are parallel to the axis of this tectonic structure. The obtained results suggest that the Ponta Grossa Arch influenced the deposition of the carbonate and evaporite facies of the Teresina Formation, acting as a geographical barrier that restricted the entry of ocean waters from south. This promoted reduced terrigenous input, low water circulation and the increase of salinity in the northern flank of the PGA. Furthermore, a possible winds convergence zone, parallel to the Ponta Grossa Arch, would affected the climatic conditions in the study region during the Late Permian, difficulting the northward migration of wet air masses coming from the Panthalassa Ocean. This favored arid conditions in the study area. The tectonic and climatic significance of the carbonate and evaporite facies of the Teresina Formation have important implications for correlations between the Paraná Basin and basins from Africa, such as the Karoo and Huab basins, as well as for paleogeographic reconstructions of the Gondwana in the Permian.

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El-Sherif, Noran MHM. "Palaeoecological Analysis of the Decline in Stromatolite Abundance during the Ordovician Period." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1369749773.

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18

Lepot, Kevin. "Recherche et caractérisation de traces fossiles d'activité microbienne archéenne (Pilbara Drilling Project, Australie)." Paris, Institut de physique du globe, 2007. http://www.theses.fr/2007GLOB0007.

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Les stromatolites, dépôts carbonatés aux morphologies singulières, sont parmi les plus notables Archéenne (2,5 à 4 milliards d'années). Si on sait que de tels dépôts se forment sous l'influence de tapis microbiens dans lesenvironnements modernes, l'origine biologique des stromatolites "fossiles"Archéensreste débattue. L'utilisation de techniques de microscopie et spectroscopie de haute résolution a permis d'étudier la matière organique et les minéraux associés directement au sein de la roche jusqu'à l'échelle du nanomètre. Cette étude a révélé la présence de globules de matière organique évoquant des microorganismes procaryotes dans les stromatolites de Tumbiana (2,7 milliards d'années). Ces globules sont intimement associés à des nano-cristaux d'aragonite. La haute similitude de cette association avec les nanocomposites organo-minéraux formant les stromatolites modernes défend l'origine biologique des stromatolites de Tumbiana. Cette aragonite, présumée hautement instable, est 2,3 milliards d'années plus ancienne que les autres aragonites découvertes jusqu'alors. L'étude systématique des associations organo-minérales dans ces stromatolites montre l'absence de textures caractéristiques d'une remobilisation de matière organique en association avec les globules, ce qui soutient leur interprétation en tant que microbes fossiles. Cette distribution, ainsi que la spectroscopie (NEXAFS, EDX) de la matière organique, suggèrent de plus que la préservation des globules est liée à une action commune de la sulphurisation de la matière organique et de son encapsulation par les minéraux

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Romero, Guilherme Raffaeli. "Geobiologia de microbialitos do Ediacarano da Faixa Paraguai e do sul do Cráton Amazônico (MS e MT): implicações paleoambientais, paleoecológicas e estratigráficas." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-24022016-095246/.

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A Faixa Paraguai é uma faixa de dobramentos neoproterozoicos ao sul do Cráton Amazônico. No Brasil, está, localizada nos estados de Mato Grosso e Mato Grosso do Sul. Esta faixa tem sido alvo de constantes discussões sobre questões paleoambientais, paleoecológicas e evolutivas globais, uma vez que, em suas unidades ocorrem depósitos pós-glaciais marinoanos, as chamadas capas carbonáticas, típicas do inicio do Ediacarano, além de Cloudina lucianoi, fóssil índice do Ediacarano final, associado a outros metazoários. Nesta tese, foram estudados oito afloramentos: três pertencentes à Faixa Paraguai Sul- Formação Bocaina (FB) - Grupo Corumbá e cinco, à Faixa Paraguai Norte- Grupo Araras, sendo dois afloramentos na Formação Mirassol D\'Oeste (FMO), base do grupo e três afloramentos na Formação Nobres (FN), última formação do Grupo Araras. No total foram analisadas 73 amostras representativas de estromatólitos e 37 lâminas petrográficas de estromatólitos e rocha encaixante. Em três afloramentos, definidos como capas carbonáticas, a análise e a comparação entre a associação de estruturas tubulares e estromatólitos indicou que estas estruturas sedimentares são um importante marcador estratigráfico dos depósitos de capas carbonáticas Marinoanas. No entanto, as estruturas previamente descritas como tubulares no afloramento de Porto Morrinhos (FB), são interpretados aqui como estromatólitos colunares sem associação com os eventos do início do Ediacarano. Com a caracterização das associações de estromatólitos e estruturas tubulares nos afloramentos de Morraria do Sul e Forte de Coimbra, foi proposto, neste trabalho, que estes afloramentos não fazem parte da Formação Bocaina, e sim cronocorrelatos à Formação Mirassol D\'Oeste, no inicio do Ediacarano. O escape de fluidos foi considerado a explicação mais adequada para a origem das estruturas tubulares, corroborando alguns estudos originais. Neste sentido, é provável que o fluido tenha se originado do acúmulo de matéria orgânica nos estromatólitos. A comparação entre diferentes ocorrências de estruturas tubulares indicaram que estas possuem uma origem comum, porém, diferem em relação a sua história sedimentar. Em alguns ambientes, as estruturas tubulares eram espaços abertos na interface água-sedimento, enquanto que em outros eram espaços sem esse tipo de contato. A textura dos microbialitos de capas carbonáticas é composta por peloides amalgamados em grumos arredondados interpretados como restos micritizados de colônias cocooidais de cianobactérias. A alternância laminar observada na Pedreira Terconi pode ser relacionada a mudanças sazonais das comunidades dominantes. Os laminitos microbianos de capa carbonática formaram-se em plataformas bem iluminadas, calmas, abaixo do nível de ondas de tempestade, sem contribuição de siliciclásticos, concordante com o ambiente transgressivo proposto para o pós-glacial. A Formação Mirassol D\'Oeste, base do Grupo Araras, apresenta aproximadamente 10 metros de laminitos microbianos seguidos de camadas de megamarcas onduladas com lentes de megapelóides gerados pela ação de ondas de \"hypercanes\" que ocorreram durante a deposição das capas carbonáticasMarinoanas. Estes furações e a ação de ondas foram o motivo para o fim da deposição microbiana na Formação Mirassol D\'Oeste. Na Formação Nobres, última formação do Grupo Araras, foram identificados 15 níveis de estromatólitos, silicificados. A silicificação ocorreu durante a diagênese, obliterando em muitos níveis a laminação estromatolítica. Os estromatólitos da Formação Nobres foram divididos em quatro associações de morfotipos. A distribuição, desenvolvimento e abundância dos morfotipos foi regida por fatores sedimentológicos, devido a variações do nível do mar. O fim dos estromatóltios da Formação Nobres é concomitante com o fim da sedimentação carbonática do Grupo Araras. A evolução dos estromatólitos do Grupo Araras revelou uma variação nas formas e participação dos estromatólitos na composição litofaciológica desta plataforma carbonática. Na Formação Mirassol D\'Oeste, os estromatólitos são abundantes e considerados um dos principais componentes arquiteturais da plataforma carbonática, enquanto na Formação Nobres, apesar da alta frequência e variação de morfotipos dos estromatólitos, a contribuição na composição litofaciológica da plataforma carbonática é mínima. As variações de formas e abundância dos estromatólitos ao longo do Grupo Araras sugerem mudanças em relação importância dos microbialitos na composição das unidades estratigráficas, bem como a alteração nas condições de sedimentação do sistema deposicional -variação do nível do mar e influxo de siliciclásticos- do Grupo Araras.
The Paraguay Belt is a Neoproterozoic fold belt at the south of the Amazon Craton. In Brazil, the Paraguay belt is located in the states of Mato Grosso and Mato Grosso do Sul, central Brazil. The Paraguay Belt has been the subject of constant discussion of paleoenvironmental, paleoecological and evolutionary questions, since, in their units occur the Marinoan post-glacial deposits, the so called \"cap carbonates\", typical of the beginning of the Ediacaran, and Cloudina lucianoi, index fossil of the late Ediacaran, associated with other metazoans. In this thesis, eight outcrops were studied: three belonging to the Southern Paraguay Belt -Bocaina Formation (FB)-Corumbá Group and five outcrops belonging to the Northern Paraguay Belt- Araras Group, two outcrops in Mirassol D\'Oeste Formaton (FMO), the group\'s base and three outcrops in the Nobres Formation (FN), the last unit of the Araras Group. In total 73 representative samples of stromatolites and 37 thin sections of stromatolites and host rock were analyzed. In three outcrops, defined as cap carbonates, analysis and comparison of the tubestone structures and microbial laminites association indicated that these sedimentary structures are an important stratigraphic marker for the deposits of Marinoan cap carbonates. However, the tubular structures previously assigned as tubestone structures in Porto Morrinhos outcrop (FB) are interpreted here as columnar stromatolites unassociated with the events of the early Ediacaran.With the characterization of the tubestone-stromatolite association in the outcrops of Morraria do Sul and Forte de Coimbra, it was proposed in this study that these outcrops are not part of Bocaina Formation but are cronocorrelated to MirassolD\'Oeste Formation, at the beggining of the Ediacaran. The fluid escape was considered the most suitable explanation for the origin of tubestone structures, corroborating some original studies. Therefore, it is likely that the fluids had originated from the accumulation of organic matter in the stromatolites within the cap carbonates. The comparison between different occurrences of tubular structures indicated that they have a common origin, however, differ in their sedimentary history. In some environments, the tubular structures were open spaces in the water-sediment interface, while others were in areas the structures were without such contact. The texture of cap carbonate microbialites comprises peloids amalgamated into rounded microclots interpreted as micritization remains of cocooidal colonies of cyanobacteria. The laminar alternation observed in the quarry Terconi (Mirassol D\'Oeste Formation) may be related to seasonal changes of the dominant communities. The microbial laminites of the Marinoan cap carbonates formed in well-lit platforms, calm, below the level of storm waves, without contribution of siliciclastic, concordant with the transgressive environment proposed for the post-glacial. At the Mirassol D\'Oeste Formation, base of the Araras Group, approximately 10 meters of microbial laminites where described, covered by a packstone deposit of megaripple marks with megapeloid lenses generated by the action of wave \"hypercanes\" that occurred during the deposition of the Marinoan Cap Carbonates. These hypercanes and the wave action were the reason for the waning of microbial deposition in Mirassol D\'Oeste Formation. In the Nobres Formation, at the upper part of the Araras Group, 15 levels of silicified stromatolites were identified. The silicification occurred during late diagenesis, obliterating many portions of stromatolitic lamination. Stromatolites of Nobres Formation were divided into four morphotypes associations. The distribution, development and abundance of morphotypes was governed by sedimentological factors, due to sea level variations. The end of stromatolites in the Nobres Formation is concomitant with the end of carbonate sedimentation of the Araras Group. In Mirassol D\'Oeste Formation, stromatolites are plentiful and considered one of the major architectural components of the carbonate platform, while the Nobres Formation, despite the high frequency and morphotypes variation of stromatolites, the contribution in the litofaciological composition of carbonate platform is minimal. The variations of forms and the abundance of stromatolites along the Araras Group suggest changes regarding importance of microbialites in the composition of stratigraphic units as well as the change in the depositional system - variation in sedimentation conditions of the sea level and the influx of terrigenous in the Araras Group.

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20

Urlwin, Benjamin. "Neoproterozoic carbonates of the Jasper region, sedimentology, stratigraphy and stromatolite morphology." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq24703.pdf.

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21

Savage, Derek Allan. "Terminal proterozoic stromatolite reefs with shelly fossils, Salient Platform, British Columbia." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81434.

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The late Neoproterozoic Salient Platform (Byng Formation, upper Miette Group), located 50 km northwest of Jasper, Alberta, contains one of three known occurrences worldwide of the Cloudina-Namacalathus fossil assemblage.
The Salient Platform initiated in relatively deep water (minimum 30-50 m) on Mount Machray. Lowermost carbonates on Salient Mountain and The Colonel were deposited in quiet environments behind the developing stromatolitic reef. The upper two thirds of the platform formed in shallow water and consists of huge, elongated Platella and Cryptozoon bioherms, within which most shelly fossils are found. Carbonate production is terminated by Gog Group siliciclastic sedimentation. Thin, shell-bearing stromatolitic carbonates discovered within the lowermost Gog Group bring into question the current position of the Precambrian-Cambrian boundary in the southern Rocky Mountains (western Canada).
Petrographic and geochemical data indicate that the Salient Platform has undergone significant diagenetic alteration. delta13C values of microsparitic limestones appear to retain a primary isotopic signature, which correlates well with coeval late Neoproterozoic successions worldwide.

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Flatt, P. M., C. Damarjanan, E. Isamonger, J. C. J. Kalinski, Rosemary Dorrington, and K. L. McPhail. "Stromatolite microbial communities as a source of new bioactive secondary metabolites." Georg Thieme Verlag KG, 2016. http://hdl.handle.net/10962/65871.

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Stromatolites represent some of the earliest microbial communities on Earth. They are formed by accretion and precipitation of layered calcium carbonate structures that result from the metabolic activity of complex microbial communities and the geochemical conditions of their environment. Modern stromatolite communities include aerobic heterotrophs, sulphide-oxidizing bacteria, sulphate-reducing bacteria, fermentative bacteria and cyanobacteria. Phylogenetic analyses revealed the presence of new and known cyanobacterial taxa related to known producers of biologically active secondary metabolites in tufa stromatolites along the South African southeast coast [1]. Prompted us to investigate their potential for producing novel bioactive secondary metabolites. A series of three tide pools provided the opportunity to collect stromatolites along a vertical transect from pool A (highest elevation, low nitrogen input, fresh water), pool B (within high tide zone, brackish water) and pool C (within tidal zone). The microbial community in pool A is particularly distinct. Chemical extracts of stromatolites from different pools have been profiled by LC-MS/MS and the data subjected to molecular spectral networking using the GnPS platform [2] in order to establish the diversity and biological potential of the microbial metabolome that is being expressed within each of these microhabitats. Correlation of the phylogenetic and secondary metabolomic data is expected to guide the isolation of new natural products with biomedical relevance.

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23

Garnier-Caudwell, Christiane. "Eude expérimentale de la croissance de stromatolithes a rivularia actuels et subactuels, d'eau douce, en climat tempéré." Dijon, 1995. http://www.theses.fr/1995DIJOS043.

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Des stromatolithes a rivularia haematites (d. C. ) Agardh et a rivularia biasolettiana meneghini, prélevés sur le plateau de Langres (France) en milieu palustre, ont été suivis sur le terrain, transplantes en milieu fluviatile et cultives sur des milieux favorables dans des conditions de température et d'éclairement variables suivant des cycles jour-nuit. Chez rivularia haematites, la formation d'une bande sombre micritique se fait en trois étapes. La première correspond à l'édification uniquement biologique de zones sombres, ou niveaux à gaines, grâce à l'alignement des heterocystes et des fausses ramifications édifiées pendant une saison humide (septembre à mai dans le contexte étudié). La deuxième se traduit par la calcification des zones sombres sous forme d'ensembles polycristallins microsparitiques ou sparitiques réunissant sept à huit filaments. Les dimensions et l'orientation (transversale, longitudinale et circulaire) des microfibrilles de la gaine permettent de localiser les sites de nucléation sur ces dernières et d'expliquer la structure tridimensionnelle des cristaux et des ensembles polycristallins. Dans une troisième étape, une prolifération bactérienne estivale dans le mucilage des gaines induirait une micritisation de la microsparite ou de la sparite des zones sombres par un processus de dissolution-recristallisation. Les deux dernières étapes nécessitent des phénomènes évaporatoires et, par conséquent correspondent à des étés chauds et secs. Une zone claire sparitique se formerait par l'edification biologique de niveaux pilifères et poreux et par un remplissage sparitique ou microsparitique des pores. L'absence de micritisation ultérieure s'explique par l'inexistence de gaines autour des poils. L'espacement dans le temps de ces différentes étapes fait qu'un doublet zone claire sparitique-zone sombre micritique s'édifie en deux ou trois années. Chez rivularia biasolettiana, les heterocystes et les fausses ramifications n'étant pas alignes en bandes, il n'y a pas de zones sombres et claires. Il s'ensuit une dispersion des ensembles polycristallins et une micritisation générale du stromatolithe

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Eagan, Keith E. "Paleoenvironmental and Stratigraphic Interpretation of the Middle Cambrian Ute Formation, Northern Utah." DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/6791.

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The Middle Cambrian Ute Formation includes some 200 m of cyclically alternating carbonates and mud rocks. These are arranged in eight to nine, meter-scale, shallowing-upwards packages, representing deposition under predominantly subtidal conditions. The packages consist of vertical sequences of shale, silty limestone, oncolitic packstone, and oolitic grainstone that exhibit little variance in this general pattern. Small-scale unconformities separate the packages. The inferred depositional environment consists of an intrashelf basin that has a peritidal platform near its margins. The craton, which supplied most of the terrigenous sediment, was situated to the south (Cambrian orientation), and located near the equator. One cycle includes a stromatolite biostrome that is distributed across more than 1500 km2 in northern Utah and southern Idaho. Stromatolites range from mound-like to club-shaped to columnar and reach up to 2 min vertical dimension, and 0.15 min diameter. These large columnar structures were apparently established just basinward of an oolitic shoal. These ancient stromatolites, which are in many ways similar to those stromatolites recently reported from the Bahamas, contain many clues that suggest that they grew in normal marine conditions. These findings require a rethinking of the commonly held belief that Phanerozoic columnar stromatolites are indicators of restricted, hypersaline conditions. Analysis of several orders of laminae in Ute Formation stromatolites indicates periodicity in accumulation from which yearly accumulation rates may be inferred. Values obtained for growth rate range from 4.39-4.88 cm/yr. Such rates of accumulation are in accord with those documented for ancient stromatolites from the Bitter Springs Formation. Thus, even considering the occurrence of hiatal surfaces within the stromatolites, the duration of the columnar-stromatolite horizon probably encompasses 10-2 - 10-3 yr. The biostrome's position in the sequence of cycles and the changes in stromatolite morphology across depositional dip suggest that the biostrome may be essentially isochronous across its outcrop area and, thus, may be viewed as a bioevent horizon. The stromatolites also contribute to a better understanding of the paleogeography of the study area during the Middle Cambrian by providing information on relative energy levels and flow directions. (212 pages)

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Blanco, Angélica Maria. "Processos organo-sedimentares da Lagoa Salgada (RJ, Brasil) durante os últimos 7000 anos A.P. : implicações paleoambientais." Niterói, 2016. https://app.uff.br/riuff/handle/1/1541.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ
O desenvolvimento de planícies costeiras e a evolução de ambientes deposicionais Fúlviolagunares e depósitos praias deu origem a diversas lagoas ao longo da costa do Estado do Rio de Janeiro. Os sistemas lagunares estiveram influenciados pelas variações do nível do mar com sedimentos oriundos de diversas fontes. Como consequência das flutuações do nível do mar, os sistemas lagunares formados apresentaram características especiais como mistura de águas continentais e marinhas, geralmente com alta salinidade. Este trabalho caracteriza a sedimentação do paleoambiente da lagoa Salgada com uso de isótopos 13C, 15N, do 14C e C:N na matéria orgânica (MO) do testemunho S15. Foi construído um modelo cronológico, através de regressão linear resultando em um período compreendido entre 6.300 e 1.300 anos cal. AP. Devido à complexidade nas interpretações paleoambientais e sedimentológicas de ambientes de planícies deltáicas, assim como a identificação das fontes de MO, os processos de sedimentação foram analisados através da litologia e história evolutiva do lago. O testemunho S-15 foi dividido em três unidades (I, II e III) e nove sub-unidades litológicas (A, B, C, D, E, F, G, H e I) de modo a correlacionar os sedimentos e a MO e assim compreender os processos de sedimentação na lagoa nos últimos 7.000 anos. Os sedimentos são siliciclásticos com fases intercaladas de lama arenosa e lama síltico-argilosa, isto sugere uma sedimentação lacustre num sistema com variações de energia. A geoquímica isotópica do testemunho S-15 mostrou pouca variação ao longo da sucessão sedimentar. A variabilidade dos valores do 13C e do 15N ao longo do testemunho sugere três fases de sedimentação orgânica (fluvial, estuarina e lagunar) devido à transição do ambiente marinho a lagunar, influenciado pela evolução deltáica. Os valores C:N sugerem mistura de fontes de MO alóctone e autóctone (plantas terrestres C3, bactérias e fitoplâncton). O clima semiárido na região, em consequência da ressurgência costeira e fechamento do sistema lagunar, favoreceu a precipitação de sais e carbonatos uma vez que a lagoa ficou isolada na planície costeira. Assim, a geoquímica e os processos de sedimentação mudaram gerando condições específicas para o desenvolvimento de tapetes microbiais e, posteriormente para o topo da sucessão, os estromatólitos.
The development of coastal plains and the evolution of fluvial-lagoonal depositional environments and beach deposits gave rise to several lakes along the Rio de Janeiro State coast. The lagoonal systems were influenced by the sea level variations with sediments from different sources. As a consequence of the fluctuations in sea levels, the lagoonal systems presented special features as a mixture of continental and marine waters, usually with high salinity. This study characterizes the sedimentation of the paleo-environment of Salgada lake, using 13C, 15N isotopes, 14C and C:N in the organic matter (OM ) of the core S-15. It was constructed a chronological model based on linear regression resulting in a period between 6.300 and 1.300 yrs cal. BP. Due to the complexity on paleoenvironmental and sedimentological interpretations in delta plain environment as well the identification of OM sources, the sedimentation processes were analyzed trough the lithology and evolutionary history of the lake. The S-15 core was divided into three units (I , II, and III) and nine lithological sub-units (A, B, C , D, E , F, G , H and I) in order to correlate the sediments and the OM and therefore to understand the lake sedimentation processes in the last 7.000 years. The sediments are siliciclastic with intercalated phases of sandy mud- and clay silt mud -. This suggests a lacustrine system with variations in energy. The isotopic geochemistry of S- 15 core showed little variation throughout the sedimentary succession. The variability of 13C and 15N values along the core suggests three phases of organic sedimentation (fluvial, estuarine and lagoonal) due to the transition from the marine to lagoonal environment, influenced by the deltaic evolution. The C:N values suggests mixing sources of allochthonous and autochthonous OM (C3 terrestrial plants, bacteria and phytoplankton). The semiarid weather in the region, as a consequence of coastal upwelling, and closure of the lake system favored the precipitation of salts and carbonates, since the lagoon was isolated in the coastal plain. Therefore the geochemistry and the sedimentation processes changed generating specific conditions for the development of microbial mats and further, to the top of the succession, the stromatolites.

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Nitti, Anthony G. "Microbialites from the Freshwater System of Cuatro Ciénegas, Mexico: Genomic, Molecular Organic, and Stable Isotopic Perspectives." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3618.

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Modern microbialites are carbonate-precipitating microbial mats and represent the closest living analogues to ancient stromatolites. These ancient carbonate formations are the oldest fossil evidence of life on Earth; however, our comprehension of their relationship to early earth ecosystems relies heavily on understanding the formation of modern microbialites. Research regarding these formation processes has suggested that chemical constraints of CaCO 3 precipitation vary on sub-millimeter spatial scales within the living microbial community. In an attempt to shed light on the importance of these chemical microenvironments, this study focused on understanding the spatial distribution of the organisms and processes involved in the formation of modern microbialites. This was accomplished by isolating five visually distinct layers from the upper 2 – 3 cm of an actively forming microbialite found in the freshwater system of Cuatro Ciénegas, Mexico. Each layer was analyzed using genomic, molecular organic, and stable isotopic techniques. Bacterial diversity was determined by 16S rRNA gene analyses, lipid biomarker content was detected by GC-MS, and carbon isotope composition of organic matter and CaCO 3 were used as indicators of specific microbial processes. Results of the 16S rRNA gene analysis showed that there is little overlap in the community composition of individual layers. Approximately 90% of the ribotypes identified in the microbialite were unique to a single layer. Furthermore, the relative accretion of CaCO 3 at each layer was used to connect the distribution of organisms and processes with two specific zones of CaCO 3 precipitation. The first zone of CaCO3 accretion, which accounted for approximately 55% of total CaCO 3 accumulation, is found in the surface two layers of the microbialites and dominated by photoautotrophic cyanobacteria and algae. The second zone of CaCO 3 precipitation, found at the interior (layers 4 and 5), is composed primarily of heterotrophic proteobacteria and dominated by sulfate-reducing !-proteobacteria. The lipid content of the microbialite reflected the community structure as determined by genomics. Numerous photosynthetic biomarkers were detected and decreased in abundance with depth, indicating the important function of heterotrophic degradation. Additionally, the detection of sulfurized phytol compounds in layer 5 highlighted an important mechanism for the preservation of biogenic signatures, and reflected both the abundance of phototrophic organisms and sulfatereducing bacteria. In combination, these interdisciplinary analyses provided an understanding of microbial community composition and metabolism while indicating the spatial relationship to CaCO 3 formation and the preservation of distinct biochemical signatures. !

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Filho, William Sallun. "Análise dos Estromatólitos do Grupo Itaiacoca (Proterozóico), ao Sul de Itapeva, SP." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/44/44136/tde-10052010-165919/.

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Estromatólitos foram estudados em nove localidades ao sul de Itapeva (SP), principalmente em metacalcários dolomíticos cinza-claro e, secundariamente, em metacalcários calcíticos cinza-escuro, do Grupo Itaiacoca, uma unidade vulcanossedimentar mesoproterozóica da Faixa Ribeira. Foram diferenciados em cinco formas colunares, a mais comum consistindo de colunas coniformes, não ramificadas, de diâmetros e alturas centimétricas a decimétricas, atribuídas a Conophyton. As outras quatro formas, com laminação convexa mas não coniforme, diferem em tamanho, silhueta e estilo/freqüência de ramificação. As diferenças na preservação dos estromatólitos são relacionadas ao comportamentos tectônicos distintos entre o metacalcário dolomítico (mais puro), com comportamento competente, e o calcítico (mais argiloso) que atuou de forma mais plástica. Nas melhores exposições desta área os estromatólitos estão agrupados em bioermas de Conophyton, sem indícios de exposição ou retrabalhamento sub-aéreo ou por ondas, evidenciando um ambiente calmo e relativamente profundo, provavelmente abaixo do nível de base de ondas, de talvez até algumas dezenas de metros de profundidade. Conophyton de Itapeva é semelhante a estromatólitos coniformes próximo a Abapã (PR), também no Grupo Itaiacoca, a cerca de 100 km de Itapeva, mas difere de outras formas, incluindo Conophyton cylindricum e C. metulum, de unidades proterozóicas associadas a margem oeste do Cráton do São Francisco. O Conophyton do Grupo Itaiacoca é semelhante a formas na ex-União Soviética que são geralmente encontrados no Mesoproterozóico ou Neoproterozóico inferior, que é consistente com as datações radiométricas disponíveis que colocam esta unidade próximo ao final do Mesoproterozóico.
Stromatolites were studied at nine localities south of Itapeva, São Paulo, Brazil, generally in light-gray metadolostones and secondarily in dark-gray metalimestones of the Itaiacoca Group, a Mesoproterozoic volcanosedimentary unit of the Ribeira Belt. Five columnar forms were distinguished, the most common consisting of unbranched, coniform columns, with centimetric to decimetric diameters and heights, attributed to Conophyton. The other four forms exhibit convex, but not coniform lamination and differ in size, silhouette and style/frequency of branching. Differences in stromatolite preservation are related to the differing tectonic behavious of the purer and more competent metadolostones and the more argillaceous metalimestones which behaved more plastically. In the best exposures in this area the stromatolites are grouped into Conophyton bioherms, without any evidence of subaerial exposure or reworking by waves, which suggests that they formed in a calm and relatively deep setting (perhaps up to several tens of meters in depth), probably below the base of fairweather water. Conophyton from Itapeva is similar to other coniform stromatolites in the Itaiacoca Group near Abapã (Paraná), about 100 km SW of Itapeva, but differs from other forms, including Conophyton cylindricum and C. metulum, from Proterozoic successions associated with the western margin of the São Francisco Craton. The Conophyton from the Itaiacoca Group is most similar to forms in the ex-Sovietic Union that are usually found in the Mesoproterozoic or lowest Neoproterozoic, which is consistent with available radiometric age dates that place this unit near the end of the Mesoproterozoic.

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Miningou, Mariette. "Genèse des indices polymétallifères des formations néoprotérozoïques (1000 – 543 Ma) dans la région du Béli (Nord du Burkina Faso) : contrôle structural, nature des fluides, rôle de la silice." Aix-Marseille 3, 2006. http://www.theses.fr/2006AIX30068.

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A l’instar des formations sédimentaires des bassins de Taoudeni et des Volta, celles de la région du Béli comportent une triade (tillite-calcaire-silexite) et une formation molassique. Ces marqueurs stratigraphiques ont permis la subdivision verticale des ensembles sédimentaires des bassins ouest-africains en trois surpergroupes. La triade repose sur des grès-quartzites et est surmontée par des shales et des dolomies. Comme les formations carbonatées, certaines roches du complexe silexitique renferment des stromatolites, de même que des micro-organismes. Dans la région du Béli, excepté le deuxième, on reconnaît les quatre épisodes tectoniques de l’orogenèse panafricaine dont les caractéristiques permettent de distinguer deux unités structurales. L’unité structurale du Nord-Béli (allochtone), caractérisée par une déformation de type ductile et un anchimétamorphisme, est charriée sur l’unité structurale du Sud-Béli (para-autochtone). Celle-ci est marquée par une déformation à dominante cassante, n’a subi aucun métamorphisme et est chevauchant sur le socle birimien. Le réseau de fractures intéressant la région du Béli a favorisé la circulation de fluides de températures variées et d’origines diverses (météoriques, marines, saumâtres, épithermales). Ces fluides sont responsables de la présence des abondantes expressions siliceuses, mises en place en au moins deux phases. Les fluides hydrothermaux, par lessivage des formations silexitiques et schisteuses, et probablement du socle birimien, ont favorisé le dépôt, sous forme de sulfures, de nombreux métaux, préférentiellement dans les zones des brèches silexitiques. Celles-ci comportent l’essentiel des affleurements ferrugineux dont la plupart ont été reconnus comme étant des chapeaux de fer
As in Taoudeni and Volta basins sedimentary formations, whose in the Beli region include a triad (tillite-limestone-chert) and a molassic formation. These stratigraphic markers have permitted the vertical subdivision of these western african basins sedimentary set in three supergroups. The triad overlay quartzitic sandstone and is overlaid with shale and dolomite. As in the carbonated formations, some rocks of the cherty complex contain stromatolites, as well as micro-organisms. In the Beli region all four pan-african orogeny tectonic episods are recognized except the second one. Their features permit to distinguish two structural units. The structural unit of the North-Beli (allochthonous), characterized by a ductile type distortion and an anchimetamorphism, is carried along the structural unit of the South-Beli (para-autochthonous). This one is marked by a dominant brittle distortion, it is non metamorphic and overlaps the birimian basement. The network of fractures in the Beli region favored fluids circulation of varied temperatures and various origins (meteoric, marine, brackish, epithermal). These fluids are responsible of the abundant silica expressions presence, that put in place in at least two phases. The hydrothermal fluids, by leaching of cherty and slaty formations, and probably of birimian basement, led to many metals deposit, preferentially as sulphides, in cherty brecciated zones. These include essential of the ferruginous outcrops of which most have been recognized as being gossans

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Xu, Baiquan. "Microfacies, Carbon and Oxygen Isotopes of the Late Archean Stromatolitic Carbonate Platform of the Kaapvaal Craton, South Africa: Implications for Changes in Paleo-environment." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-137794.

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30

Garcin, Manuel. "Le bassin de San Miguel de Salinas (Alicante, Espagne) : relations entre contexte structuro-sédimentaire et dépôts évaporitiques et carbonates au Messinien." Paris 11, 1987. http://www.theses.fr/1987PA112027.

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Cette étude traite de l'évolution d'un bassin messinien, a termes évaporitiques du Levant espagnol ainsi que de son histoire pliocène et quaternaire. Dans un premier temps, l'analyse des dépôts, sous les aspects lithologique, sédimentologique et micropaléontologique est effectuée; des évaluations bathymétriques et paléoenvironnementales en sont dégagées. Les rapports géométriques des différents corps sédimentaires et notamment ceux des carbonates et des évaporites du Messinien, sont déduits de la carte au I:25000 et des observations de terrains. Différents processus sédimentaires aussi bien chimiques (sulfates), biosédimentaires (constructions à Annélides, stromatolithes, récifs à Algues rouges et Porities) que tectono-sédimentaires (séismites) sont abordés dans des études thématiques. Une troisième partie dégage l'importance des mouvements tectoniques et leur interactions sur la sédimentation notamment au Messinien et à la limite mio-pliocène où des olistolithes se mettent en place tandis que des failles normales sont responsables de la complète réorganisation de la paléogéographie. La quatrième partie est consacrée à la reconstitution du bassin de San Miguel de Salinas et de ses bordures carbonatées tant sous les aspects sédimentologique, bathymétrique, géométrique, paléoécologique que d'un point de vue tectono-sédimentaire
This study treats a messinian basin evolution, with evaporitic final stage, pliocene and quaternary history, in SE Spain. First, deposits analysis with particular development of lithologic, sedimentologic and micropaleontologic aspects are gived. Bathymetric and paleoenvironmental evaluations are deducted. Geometric relations between sedimentary units and specially all of messinian age are interpreted from field and map observations. Differents sedimentary processes as chemical (gypsum), biosedimentary (Worm reefs, stromatolites, Coral and red Algal reefs) as tectono-sedimentary (seismites) are exam in thematic studies. Third, importance of tectonic activities and their interaction with sedimentation are analysed and specially during Messinian and Nio-pliocene events when olistolites and normal faults play, all of wich play an important part in modification of palaeogeography. Last part, synthesis and basin history reconstitution are do with development of sedimentologic, bathymetric, geometric, palaeoecologic and tectono-sedimentary aspects

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31

Siahi, Mehrnaz [Verfasser], and Ernst [Akademischer Betreuer] Hegner. "A sedimentological and geochemical study of stromatolitic carbonate rocks of the Mesoarchaean Pongola Supergroup, South Africa, and inferred environmental conditions / Mehrnaz Siahi ; Betreuer: Ernst Hegner." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1125883952/34.

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32

Couradeau, Estelle. "Géomicrobiologie des microbialites du lac alcalin d'Alchichica (Mexique)." Phd thesis, Université Paris-Diderot - Paris VII, 2012. http://tel.archives-ouvertes.fr/tel-00934407.

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Les stromatolites sont des structures organo-sédimentaires formées grâce à l'activité des microorganismes. Ils dominent le registre fossile Précambrien et sont parmi les plus anciennes traces potentielles de vie sur Terre (datées à 3,5 Ga). Cependant les processus biotiques et abiotiques à l'origine de leur formation restent peu compris et ouvrent des débats sur leur interprétation. L'objectif central de ce travail est de contribuer à améliorer notre compréhension de la formation des microbialites modernes, en particulier du rôle et du devenir des microorganismes dans ces systèmes afin de mieux contraindre l'interprétation du registre fossile des stromatolites. Pour cela, nous avons étudié le système modèle des microbialites vivants du lac alcalin d'Alchichica (Mexique). La première partie de ce travail a été dédiée à la description générale des microorganismes et des minéraux du système. Les microbialites d'Alchichica sont composés d'aragonite [CaCO3] et d'hydromagnésite [Mg5(CO3)4(OH)2*4(H2O)]. L'analyse de la diversité microbienne par des méthodes moléculaires basées sur le clonage et le séquençage du SSU rDNA a révélé une grande diversité dans le domaine des bactéries (344 phylotypes répartis dans 21 phylums) et des eucaryotes (58 phylotypes répartis dans 9 phylums) en regard d'une faible diversité d'archées (2 phylotypes). Des analyses de phylogénie moléculaire ont permis d'attribuer ces phylotypes environnementaux à différents taxons et d'identifier les représentants cultivés les plus proches, ce qui a permis de définir les groupes métaboliques potentiellement importants dans ce système. Dans les microbialites d'Alchichica, la photosynthèse oxygénique est réalisée par les cyanobactéries, les algues vertes et les diatomées. Une grande diversité d'organismes incluant des membres des Alpha-proteobacteria et des Chloroflexi réalisent quant à eux la photosynthèse anoxygénique. Si le biofilm est dominé par les organismes autotrophes en termes de biomasse, la diversité taxonomique des organismes hétérotrophes s'est révélée supérieure. Nous avons notamment identifié des membres des Deltaproteobacteria et des Firmicutes réalisant la sulfato-réduction, ainsi qu'une grande diversité de taxons capables de dégrader des molécules organiques complexes tels que les Planctomycetales, les Bacteroidetes et les Verrucomicrobia. Ces résultats nous ont permis de construire un modèle hypothétique des réactions métabolico-géochimiques contribuant à la précipitation ou dissolution des carbonates au sein des biofilms des microbialites d'Alchichica. Dans la seconde partie de ce travail, nous avons décrit une association préférentielle entre les colonies de cyanobactéries de l'ordre des Pleurocapsales et l'aragonite. Nous avons pour cela couplé différentes techniques de microscopie et de spectroscopie. Nous avons décrit un gradient de fossilisation de ces cellules dans l'aragonite jusqu'à la nano-échelle. Ceci a montré que l'ultrastructure des cellules des Pleurocapsales était préservée lors de la minéralisation grâce à la mise en place séquentielle d'aragonite. C'est finalement la texture de l'aragonite et non pas la présence de matière organique qui signe l'organisation originelle des cellules de Pleurocapsales. Cette étude ouvre des perspectives intéressantes dans la recherche de microfossiles de cyanobactéries dans les stromatolites fossiles. La troisième partie enfin rapporte la découverte d'un cas de biominéralisation intracellulaire contrôlée chez une cyanobactérie de l'ordre basal des Gloeobacterales. Nous avons nommé cette souche Candidatus Gloeomargarita lithophora. Les inclusions intracellulaires produites par Ca. G. lithophora sont des carbonates amorphes de Ba-Sr-Ca-Mg. Les implications de la découverte de ce nouveau patron de minéralisation dans une lignée basale de cyanobactéries pour l'interprétation du registre fossile ancien sont discutées.

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33

Xu, Baiquan [Verfasser], and Wladyslaw [Akademischer Betreuer] Altermann. "Microfacies, Carbon and Oxygen Isotopes of the Late Archean Stromatolitic Carbonate Platform of the Kaapvaal Craton, South Africa : Implications for Changes in Paleo-environment / Baiquan Xu. Betreuer: Wladyslaw Altermann." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1018615792/34.

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34

Duringer, Philippe. "Les conglomérats des bordures du rift cénozoïque rhénan : dynamique sédimentaire et contrôle climatique." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13246.

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35

Wogsland, Brittan Valhalla. "Organomineralization of Microbialites from Storr’s Lake, San Salvador Island, Bahamas: Calcium Stable Isotope Analysis using TIMS and a ⁴²Ca-⁴³Ca double spike." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587723502946554.

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Goh, Falicia Qi Yun Biotechnology &amp Biomolecular Sciences Faculty of Science UNSW. "Osmoadaptation mechanisms of cyanobacteria and archaea from the stromatolites of hamelin pool, Western Australia." 2007. http://handle.unsw.edu.au/1959.4/40719.

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The stromatolites of Shark Bay Western Australia, located in a hypersaline environment, is an ideal biological system for studying survival strategies of cyanobacteria and halophilic archaea to high salt and their metabolic cooperation with other bacteria. To-date, little is known of the mechanisms by which these stromatolite microorganisms adapt to hypersalinity. To understand the formation of these sedimentary structures, detailed analysis of the microbial communities and their physiology for adaptation in this environment are crucial. In this study, microbial communities were investigated using culturing and molecular methods. Phylogenetic analysis of the 16S rRNA gene was carried out to investigate the diversity of microorganisms present. Unique phylotypes from the bacteria, cyanobacteria and archaea clone libraries were identified. Representative cyanobacteria isolates and Halococcus hamelinensis, a halophilic archaea isolated from in this study, were the focus for identifying osmoadaptation mechanisms. The presence of osmolytes in these microorganisms was detected by Nuclear magnetic resonance spectroscopy (NMR). It was found that the cyanobacterial isolates studied utilised different osmolytes. Glucosylglycerol, unique to marine cyanobacteria was not identified; instead various saccharides, glycine betaine and TMAO were the predominant solutes present. Thus cyanobacteria are likely to possess more complex mechanisms of adaptation to osmotic stress than previously thought. Findings here also indicated that H. hamelinensis accumulates glycine betaine and glutamate instead of potassium ions. DNA molecular methods were employed to identify candidate genes for the uptake of osmoprotectants. Three putative glycine betaine transporters from Halococcus hamelinensis were identified. Functionality of one of these glycine betaine transporters was determined by complementation studies. For the first time, an archaeal glycine betaine transporter was shown to be successfully complemented in a glycine betaine transport deficient mutant (E. coli MKH13). This study has increased our understanding of how microorganisms co-exist in fluctuating environments in response to solubilisation/precipitation or dilution/evaporation processes, resulting in a hypersaline environment. It also provides an excellent platform for the identification of any novel osmolytes/compatible solutes that might have been produced by these microorganisms that have been isolated for the first time from stromatolites.

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Franks, Jonathan. "Confocal and TEM analysis of microbial communities in modern stromatolites at Highborne Cay, Bahamas." 2007. http://digital.library.duq.edu/u?/etd,115967.

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38

Kennard, John Michael. "Structure and origin of Cambro-Ordovician thrombolites, western Newfoundland /." 1989. http://collections.mun.ca/u?/theses,143677.

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Ferreira, Elton Luiz Diniz. "Improved estimation of pore connectivity and permeability in deepwater carbonates with the construction of multi-layer static and dynamic petrophysical models." Thesis, 2014. http://hdl.handle.net/2152/26422.

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A new method is presented here for petrophysical interpretation of heterogeneous carbonates using well logs and core data. Developing this new method was necessary because conventional evaluation methods tend to yield inaccurate predictions of pore connectivity and permeability in the studied field. Difficulties in the petrophysical evaluation of this field are related to shoulder-bed effects, presence of non-connected porosity, rock layers that are thinner than the vertical resolution of well-logging tools, and the effect of oil-base mud (OBM) invasion in the measurements. These problems give rise to uncommon measurements and rock properties, such as: (a) reservoir units contained within thinly bedded and laminated sequences, (b) very high apparent resistivity readings in the oil-bearing zone, (c) separation of apparent resistivity logs with different depths of investigation, (d) complex unimodal and bimodal transverse relaxation distributions of nuclear magnetic resonance (NMR) measurements, (e) reservoir units having total porosity of 0.02 to 0.26 and permeability between 0.001mD to 4.2D, (f) significant differences between total and sonic porosity, and (g) low and constant gamma-ray values. The interpretation method introduced in this thesis is based on the detection of layer boundaries and rock types from high-resolution well logs and on the estimation of layer-by-layer properties using numerical simulation of resistivity, nuclear, and NMR logs. Layer properties were iteratively adjusted until the available well logs were reproduced by numerical simulations. This method honors the reservoir geology and physics of the measurements while adjusting the layer properties; it reduces shoulder-bed effects on well logs, especially across thinly bedded and laminated sequences, thereby yielding improved estimates of interconnected porosity and permeability in rocks that have null mobile water saturation and that were invaded with OBM. Additionally, dynamic simulations of OBM invasion in free-water depth intervals were necessary to estimate permeability. It is found that NMR transverse relaxation measurements are effective for determining rock and fluid properties but are unreliable in the accurate calculation of porosity and permeability in thinly bedded and highly laminated depth sections. In addition, this thesis shows that low resistivity values are associated with the presence of microporosity, and high resistivity values are associated with the presence of interconnected and vuggy porosity. In some layers, a fraction of the vuggy porosity is associated with isolated pores, which does not contribute to fluid flow. An integrated evaluation using multiple measurements, including sonic logs, is therefore necessary to detect isolated porosity. After the correction and simulation, results show, on average, a 34% improvement between estimated and core-measured permeability. Closer agreement was not possible because of limitations in tool resolution and difficulty in obtaining a precise depth match between core and well-log measurements.
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Shiraishi, Fumito. "Microbial metabolisms and calcification in freshwater biofilms." Doctoral thesis, 2008. http://hdl.handle.net/11858/00-1735-0000-000D-F148-1.

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Perissonotto, Renzo, Tommy G. Bornman, Paul-Pierre Steyn, Nelson A. F. Miranda, Rosemary A. Dorrington, Gwynneth F. Matcher, Nadine Strydom, and Nasreen Peer. "Tufa stromatolite ecosystems on the South African south coast." 2014. http://hdl.handle.net/10962/d1014585.

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Following the first description of living marine stromatolites along the South African east coast, new investigations along the south coast have revealed the occurrence of extensive fields of actively calcifying stromatolites. These stromatolites have been recorded at regular distances along a 200-km stretch of coastline, from Cape Recife in the east to the Storms River mouth in the west, with the highest density found between Schoenmakerskop and the Maitland River mouth. All active stromatolites are associated with freshwater seepage streams flowing from the dune cordon, which form rimstone dams and other accretions capable of retaining water in the supratidal platform. Resulting pools can reach a maximum depth of about 1 m and constitute a unique ecosystem in which freshwater and marine organisms alternate their dominance in response to vertical mixing and the balance between freshwater versus marine inflow. Although the factors controlling stromatolite growth are yet to be determined, nitrogen appears to be supplied mainly via the dune seeps. The epibenthic algal community within stromatolite pools is generally co-dominated by cyanobacteria and chlorophytes, with minimal diatom contribution.

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42

Delamette, Michel. "L'évolution du domaine hélvétique entre Bauges et Morcles de l'Aptien supérieur au Turonien - séries condensées, phosphorites et circulations océaniques - Alpes occidentales franco-suisses." Phd thesis, 1987. http://tel.archives-ouvertes.fr/tel-00869784.

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Étude stratigraphique, paléontologique et sédimentologique des dépôts silicoclastiques à glauconie et à phosphorites du Crétacé moyen de la zone delphino-helvétique entre Chambéry (Savoie, France) et Sion (Valais, Suisse). Ces dépôts riches en horizons fossilifères organisés en conglomérats phosphatés polyzonaux s'intercalent entre les calcaires urgoniens à rudistes et les calcaires à plancton de Seewen. La récolte de nombreuse ammonites et l'identification des foraminifères planctoniques en section ont permis la proposition d'un cadre stratigraphique nouveau. L'étude sédimentologique révèle un agencement des dépôts albiens et cénomaniens en aires sédimentaires plus ou moins pérennes contrôlées pour partie par des discontinuités souvent érosives d'origine sous-marine. L'interprétation des taphocénoses et des associations ichnologiques permet de proposer un approfondissement d'un facteur 10 entre l'Aptien supérieur et le Turonien. La confrontation des données sédimentaires avec les travaux structuraux publiés conduit à la proposition d'un cadre paléogéographique dans lequel sont reconnus deux types de bordure pour la plate-forme helvétique: l'une progradante en direction du bassin ultrahelvétique, l'autre structurale déterminée par un haut-fond, héritage probable du rifting jurassique. L'importante distribution des dépôts condensés à minéralisations sous marines sur les marges européenne et apulienne au Crétacé moyen permet de présenter en conclusion une reconstitution possible de la trajectoire des circulations océaniques de subsurface sur la bordure NW de la Téthys.

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Burne, Robert Victor. "The Role and Significance of Authigenic Magnesium Silicates in the Organomineralisation of Microbialites in the Yalgorup Lakes, Western Australia." Master's thesis, 2016. http://hdl.handle.net/1885/107317.

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This work re-examines samples of modern microbialites collected in the 1980s from Lakes Clifton and Preston, two of the Yalgorup Lakes in southwest Western Australia. Lake Clifton contains the first convincing modern examples of thrombolites to have been recognized. It was known that aragonite mineralisation took place in these structures within near-surface biofilms. New research reveals that stevensite, a Mg-rich trioctahedral smectite, is the principal primary phase that establishes the initial structural rigidity of Lake Clifton thrombolites. Aragonite microcrystals then grow within the stevensite matrix. In adjacent Lake Preston, lithified, centimetre-scale, coniform structures occur that are similar to pinnacle-like microbial mats that grow intermittently in a small pond adjacent to the lake. Microstructures within the lithified cones confirm their microbial origin, but they have undergone four phases of mineralization; an amorphous Mg silicate phase (of smectite-like composition); some areas of Mg silicate were then partially transformed into authigenic serpentine (chrysotile and/or lizardite); aggregates of aragonite microcrystals then overprinted much of the fabric; and finally high-magnesium calcite grew as void fills and rims, as well as overprinting some of the remaining areas of the Mg silicate phase. It is concluded that syngenetic and early diagenetic carbonate mineralisation of microbialites may effectively obscure all traces of the original microbial communities, leaving only faint evidence for their organo-sedimentary origin. Secondary carbonate mineralisation of microbialites may thus eliminate the evidence of primary organomineralisation. Many published examples of apparently abiogenic but microbialite-like carbonates should be re-examined for traces of early silicate mineralisation. The discovery of microbial permineralisation of modern microbialites by Mg silicates in Lakes Clifton and Preston raises the possibility that phyllosilicates could have contributed to the early structural rigidity of some Proterozoic Stromatolites such as Conophyton. Reexamination of the literature on Conophyton tends supports this hypothesis. Finally, the significance of this research is considered in relation to ; clarifying the role of Mg silicates in microbialite organomineralisation; examining the evidence that apparently abiotic crystalline carbonate may be of secondary origin; understanding the nature of the supposed “microbialites” in Cretaceous pre-salt sequences of the proto-Atlantic rift; assessing the continuing relevance of the “microbialite” concept; and clarifying evidence for the recognition of the earliest signs of life on Earth.

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Li-HaoChen and 陳立豪. "Classification and carbon and nitrogen uptake patterns of autotrophs in conical stromatolite-forming microbial community from Yellowstone National Park hot spring." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/dsefe4.

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碩士
國立成功大學
地球科學系
104
Stromatolites, especially conical stromatolites, play an important role in transforming early Earth, are layered bio-chemical accretionary structures by the trapping, binding and cementation of sedimentary grains by microorganisms, especially cyanobacteria. Modern cyanobacterial mat from the hot springs of Yellowstone National Park (YNP) grow into macroscopic structure similar to an ancient analogs. Using high resolution imaging (TEM) and isotopic mapping (Nano-scale SIMS), we probed the carbon and nitrogen uptake patterns and dynamics in conical-stromatolite forming microbial community from the YNP hot spring, and focused on the characterization of carbon and nitrogen enrichment in autotrophs, especially cyanobacteria. We detected distinct patterns of carbon uptake and storage for cyanobacteria which belong to different subsection (I, II and III), and identified filamentous non-heterocystous cyanobacteria (subsection III) to be the main constitute of cone structure. These cyanobacteria bear unique sub-organelle structure ‘cyanophycin’, which can accumulate and storage large amount of carbon and nitrogen. This ability of carbon and nitrogen accumulation and storage may provide great advantages for competition of nutrients during the formation of conical stromatolites.

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Dissertations / Theses on the topic 'Stromatolites'

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