The ~5.6-4.8 Ma Bouse Formation, exposed along the lower Colorado River, contains a well exposed but debated record of river integration. Sedimentologic and stratigraphic analysis aid interpretation of depositional processes, relative water depth, depositional environments, stratal architecture, and basin-filling history. Data collected include detailed measured sections, facies descriptions, and fault measurements. Seven lithologically distinct units have been identified along with numerous marine sedimentary structures and fossils. The Bouse Formation preserves a systematic sequence-stratigraphic architecture that records two cycles of base level rise and fall. Lacustrine versus estuarine interpretation remains elusive, though new isotope and micropaleontology data suggest a shift from marine to lacustrine. Constructed stratigraphic facies panels reveal a wedging geometry indicative of syn- to post-depostional tilting, leading us to propose a "sag basin" model during deposition of the Bouse. Finally, the newly described Bouse upper limestone unit resolves a long-standing debate over the age of the first through-going river.

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

Este trabalho foi desenvolvido utilizando-se rochas reservatório siliciclásticas provenientes de afloramentos brasileiros, pertencentes ao Grupo Guaritas (Caçapava do Sul e Pinheiro Machado - RS) e à Formação Pirambóia (Rio Claro - SP), com o objetivo de se obter suas características petrofísicas. As amostras são provenientes de diferentes fácies eólicas e pluviais, com características semelhantes a reservatórios de água e hidrocarbonetos. Foram utilizados experimentos de Ressonância Magnética Nuclear (RMN), intrusão de mercúrio, susceptibilidade magnética, análise de lâmina petrográfica e Espectroscopia de Fluorescência de Energia Dispersiva de Raios-X (EDX) para a análise das amostras. Apesar de serem provenientes de sistemas deposicionais similares, a correlação entre os resultados demonstrou que a diagênese tem importante papel no desenvolvimento dos reservatórios, influenciando na porosidade e permeabilidade das amostras. Foi demonstrado que a susceptibilidade magnética possui correlação com as quantidades de Fe 203, Al 203 e SiO2, onde o Al 203 está relacionado com a quantidade de argila das amostras (aluminossilicatos). Através dos resultados de RMN foi possível estimar a susceptibilidade magnética das amostras através da largura de linha espectral em baixo campo. As estimativas de porosidade e tamanhos de poros via RMN demonstraram compatibilidade com as análises das lâminas e experimentos de intrusão de mercúrio. Com os experimentos de RMN bidimensionais T1xT2, foi mostrado que há uniformidade na relaxação, devido aos mapas de correlação serem aproximadamente paralelos à diagonal dos mapas 2D. Nos experimentos DxT2 há a correlação entre a distribuição de tempos de relaxação e coeficientes de difusão, demonstrando que, em muitos casos, há restrição de difusão translacional das moléculas do fluido. Para estimar a permeabilidade das rochas foi utilizado o modelo desenvolvido por pesquisadores da Schlumberger Doll Research (SDR), amplamente aplicado na previsão da permeabilidade através de resultados obtidos pela RMN. Aplicando-o de maneira clássica, os resultados não foram plenamente satisfatórios, em função das características magnéticas das rochas estudadas. O coeficiente relaxatividade superficial foi calculado pela convolução entre a distribuição de tamanhos de poros da intrusão de mercúrio e a distribuição de tempos de relaxação transversal. Este parâmetro foi utilizado como correção ao modelo SDR, entretanto, os resultados obtidos continuaram não satisfatórios. Foi proposta então a correção através da susceptibilidade magnética, tanto medida pelo susceptômetro quanto estimada pela RMN. As utilizações dessas duas informações culminaram em melhores resultados para o valor das permeabilidades, com destaque para a RMN, desta maneira, propondo um novo método para estimar esse importante parâmetro das rochas reservatório. Com estes resultados podemos verificar a coesão entre os aspectos geológicos das amostras e a RMN, porém, as técnicas de RMN existentes empregadas ao estudo devem ainda ser aperfeiçoadas e novas devem ser desenvolvidas para o estudo de rochas reservatório que apresentam alta susceptibilidade magnética, um problema comum encontrado no estudo de rochas sedimentares por RMN. / The petrophysical characterization of siliciclastic reservoir rocks from Brazilian outcrops was the objective of this work. The samples were obtainded from different eolian and pluvial facies of the Guaritas Group (Caçapava do Sul and Pinheiro Machado - RS) and Pirambóia Formation (Rio Claro -SP). Different methods were applied in order to study these samples: Nuclear Magnetic Resonance (NMR), mercury injection, magnetic susceptibility, petrographic thin sections analysis and Energy Dispersive X-ray Fluorescence Spectroscopy (EDX). Despite the depositional similarities, the results indicate that permeability and porosity are affected by diagenetic processes which show that the diagenesis plays an important role at the development of these reservoirs. It was shown the correlation between magnetic susceptibility and the amounts of Fe 2O3 , Al 203 and Si0 2 were the amount of Al 203 is related with the quantity of clay (aluminosilicates). Magnetic susceptibilities were estimated using the linewidth obtained from NMR spectra (by FFTs of the FIDs) measured at low and homogeneous magnetic fields, obtaining good agreement with the bulk magnetic susceptibility. Porosity and pore size distributions determined by NMR, mercury injection and petrographic analysis were compatible. In the two-dimensional NMR experiment T 1xT2 a diagonal behavior of relaxation time distributions was observed, indicating uniformity of relaxation mechanisms inside the samples. With DxT 2 measurements, the transverse relaxation times were correlated with diffusion coefficients showing restricted diffusion in most samples. In order to predict permeability the model proposed by researchers from Schlumberger Doll Research (SDR), which uses NMR parameters, was applied. With the classical permeability SDR predictor the obtained results were not fully satisfactory, as consequence of the magnetic characteristics of the samples. In order to correct this predictor, surface relaxivity coefficients were determined by the superposition of T2 and mercury injection pore diameter distributions nevertheless, these results were again unsatisfactory. Thus, a new correction method for the SDR permeability predictor was proposed using NMR and bulk magnetic susceptibilities. This approach improved considerably the permeability prediction, especially when using NMR-derived magnetic susceptibilities. The consistency between NMR and geological properties of the samples was verified nevertheless, the used NMR techniques still need to be improved and new ones must be developed, in order to allow the study of reservoir rocks with high magnetic susceptibility.

The sequence stratigraphic development of the subsurface Paleogene, Albemarle Basin, North Carolina, was defined using well cuttings and wireline logs tied into largely published biostratigraphic and available seismic data. Facies include: silty and shelly sands and shell beds (estuarine/lagoon/protected inner shelf facies); clean quartz sands and sandy mollusk-fragment grainstones (shoreface/shallow shelf); phosphatic hardgrounds (current and wave-swept shoreface and shallow shelf); bryozoan and echinoderm grainstones/packstones (storm reworked middle shelf); and fine skeletal wackestones and planktonic marls (slightly storm-winnowed to sub-wave base, deeper shelf). Paleogene deposition on this high-energy, open-shelf was characterized by a distinctive shelf profile of inner shelf and inner shelf break, deep shelf and continental shelf/slope break. The successive positions of terminal supersequence inner-shelf-breaks parallel the modern day continental margin and its onshore arches. Thickness trends were strongly controlled by more rapid subsidence within the Albemarle Basin. The Paleocene supersequence is dominated by deep shelf marl and developed following flooding after the latest Cretaceous low-stand. Major shallowing occurred at the end of the Early Paleocene and near the end of the Late Paleocene. The Eocene supersequence developed following lowstand deposition (evident on seismic) just off the terminal Paleocene depositional shelf break. With flooding, a major transgressive sediment body developed (Pamlico spur), that formed a 50 km wide by 50 m high promontory at the inner shelf break, followed by HST progradation of quartzose and bryozoan-echinoderm open shelf carbonates that filled in the laterally adjacent shelf topography. This was followed by ancestral Gulf Stream incision of the southeast-trending, shallow shelf to the south, and deep shelf further northeast. Late Eocene-Oligocene deposition was initiated with localized lowstand sedimentation off the earlier terminal inner shelf break, followed by thin regional marl deposition and widespread highstand inner shelf, quartz sands and quartzose carbonates. Localized Late Oligocene lowstand deposition occurred along the earlier Oligocene terminal inner shelf break, followed by widespread deposition of quartzose facies over the shallow shelf. Oligocene units on the deep shelf were modified by highstand Gulf Stream scour. / Ph. D.

Cores, quarry exposures, and exploratory wells in the Paleogene Albemarle Basin, North Carolina sample the transition between the southern carbonate and northern siliciclastic provinces of the eastern U.S. continental shelf succession. The study area includes the relatively positive Cape Fear Arch on the Onslow Block to the south, and the slowly subsiding (1.5 cm/ky) Albemarle Block to the north. The Paleogene supersequence set boundary is a hardground on Cretaceous shoreface/shallow-shelf mollusk facies. It is overlain by a thin Paleocene sequence of deeper offshore, glauconitic fine sands to deep marine silt-shale. Five regionally mappable, vertically stacked Eocene sequences are 0 to 30 m thick and contain coastal sands, shoreface sandy-mollusk rudstones, offshore bryozoan grainstone-packstones and subwave base fine wackestone-packstone and marl. The Eocene sequences commonly are bounded by hardgrounds, overlain by thin local lowstand sands and consist of a thin transgressive unit (commonly absent), overlain by an upward shallowing highstand marine succession. On the arch, lowstand and transgressive units may be condensed into lags. The Lower Oligocene succession on the arch has a single marl to fine foram sand dominated sequence whereas downdip, two to three sequences are developed, capped by nearshore sandy molluscan facies. The Upper Oligocene is dominated by possibly three sequences composed of basal, thin sands up into variably sandy mollusk rudstone. Sequence development was influenced by differential movement of the basement blocks, coupled with increasing 3rd order eustatic sea level changes during global cooling. This was coupled with swell-wave and current sweeping of the shelf that effectively decreased available accommodation by 20 to 30 m, and generated the distinctive hardgrounds on sequence boundaries, and variable development of lowstand and transgressive system tracts. The well developed highstands reflect maximum accommodation allowing deposition of an upward shallowing succession that terminated at the depth of wave abrasion on the open shelf. The sequence stratigraphic development contrasts markedly with that from tropical shelves. / Master of Science

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-29T23:45:59Z No. of bitstreams: 1 ANDREZZA SOUSA SILVA – DISSERTAÇÃO (PPGEPM) 2018.pdf: 5233631 bytes, checksum: 12ad47a8373c6479a15d2cbfeba06e8d (MD5) / Made available in DSpace on 2018-08-29T23:45:59Z (GMT). No. of bitstreams: 1 ANDREZZA SOUSA SILVA – DISSERTAÇÃO (PPGEPM) 2018.pdf: 5233631 bytes, checksum: 12ad47a8373c6479a15d2cbfeba06e8d (MD5) Previous issue date: 2018-03-19 / A Bacia Rio do Peixe (BRP) apresenta diversas estruturas rúpteis, dentre elas as bandas de deformação, que podem controlar as propriedades petrofísicas e aspectos texturais das rochas. Portanto, o objetivo deste trabalho é identificar os efeitos causados pelos diferentes tipos de bandas de deformação cataclásticas, em função da cinemática, sobre os aspectos texturais, distribuição de tamanho de grãos e poros, bem como porosidade em arenitos conglomeráticos. As propriedades dos grãos e dos poros foram extraídas através da análise de imagens em seções delgadas no Avizo Fire 8.1. No total foram analisadas 23 amostras, 19 com bandas de deformação (CB) com orientação definida (NW, NE, NS e EW), 2 amostras deformadas, porém sem bandas (SB) e 2 amostras da rocha hospedeira (ND). As rochas deformadas (CB e SB), apresentam redução no tamanho de grãos e pequeno acréscimo nos valores dos aspectos texturais em comparação a rocha não deformada (ND). Em relação à porosidade foi encontrada redução de 66% nas amostras CB e acréscimo de 13% nas SB. Ambos agrupamentos possuem maior conexão de grãos, permitindo o surgimento da macroporosidade, que não havia sido detectada nas amostras ND. Dentre as amostras com banda de deformação e cinemática definida, a rochas associadas ao sistema transcorrente dextral, de direção NW, possuem maior redução de diâmetro de grão, e menor redução de porosidade, cerca de 29%. As amostras com bandas de deformação NE e NS, formadas por cinemática transtensiva, são as amostras nas quais houve a menor quebra dos grãos, entretanto caracterizam-se pela presença de porosidade por fraturamento de grãos, gerando altos picos de macroporosidade. As amostras oriundas do sistema distensivo de direção EW possuem segunda maior redução de grãos, maior redução de porosidade e ausência de macroporosidade. Os aspectos texturais (circularidade, convexidade e razão de aspecto) das amostras com banda (NW, NE, NS e EW) é dependente da intensidade de cisalhamento provocado por diferentes sistemas deformacionais, quanto mais intenso mais cominuído será o grão, e consequentemente mais convexo, circular e menos alongado. Logo, é possível observar que a cinemática e a presença de bandas de deformação exercem controle sobre os aspectos texturais e petrofísicos dos arenitos conglomeráticos da Formação Antenor Navarro. E esse controle é definido pela compactação da rocha, rearranjo dos grãos, intensidade da catáclase, presença de fraturamento de grãos e cinemática atuante. / The Rio do Peixe Basin (RPB) presents several rump structures, among them the deformation bands, which can control the petrophysical properties and textured aspects of the rocks. Therefore, the objective of this work is to identify the effects caused by the different types of cataclastic deformation bands, as a function of kinematics, on the textural aspects, grain and pore size distribution, as well as porosity in conglomeratic sandstones. The grain and pore properties were extracted by thin section image analysis in Avizo Fire 8.1. In total, 23 specimens were analyzed, 19 with deformation bands (CB) with defined orientation (NW, NE, NS and EW), 2 deformed samples, but without bands (SB) and 2 samples of host rock (ND). The deformed rocks (CB and SB), present a reduction in grain size and small increase in the values of the textured aspects in comparison to the non-deformed rock (ND). In relation to the porosity, a reduction of 66% was found in the CB samples and a 13% increase in the SB. Both clusters have a larger grain connection, allowing the appearance of macroporosity, which had not been detected in the ND samples. Among the samples with deformation band and defined kinematics, the rocks associated to the dextral transcurrent system, NW direction, have a larger reduction of grain diameter, and a smaller reduction of porosity, about 29%. The samples with NE and NS deformation bands, formed by transtensive kinematics, are the samples with the lowest grain breakage. However, they are characterized by the presence of porosity by grain fracturing, generating high peaks of macroporosity. The samples from the EW steering distance system have the second largest grain reduction, greater reduction of porosity and absence of macroporosity. The textural aspects (roundness, convexity and aspect ratio) of the banded samples (NW, NE, NS and EW) are dependent on the shear strength caused by different deformation systems, the more intense the grain is, the more convex, circular and less elongated. Therefore, it is possible to observe that kinematics and the presence of deformation bands exert control over the texture and petrophysical aspects of the conglomeratic sandstones of the Antenor Navarro Formation. And this control is defined by the rock compaction, rearrangement of the grains, the intensity of the catachase, presence of grain fracture and active kinematics.

Made available in DSpace on 2015-03-13T17:08:39Z (GMT). No. of bitstreams: 1 NarelleMA_DISSERT.pdf: 7040966 bytes, checksum: 66462f8e5d4ada5ffd979bea8a0e35a9 (MD5) Previous issue date: 2014-02-21 / This work presents the results of the first imaging of continental slope adjacent to Potiguar Basin, in the equatorial Brazilian margin (NE Brazil). Swath bathymetry provided a complete coverage of seafloor between the upper and middle slope (100-1,300 m). Fifteen submarine canyons were mapped. The shape of the slope reflects in distinct spatial distribution of the canyons. The western area displays convex profiles which implied a greater amount of incisions by canyons. Some of them have gradient walls higher than 35?. They were classified according to location and morphology. The canyons with heads indenting shelf edge, association with a incised valley and a large fluvial system, high sinuosities, V shape, terraces along margins, further erosive features such as landslide and gullies allow to deduce a sandy-gravelly sedimentation. These canyons are associated with deposition of submarine fan systems that have been considered permeable hydrocarbon reservoirs. The presence of gullies, furrows and dunes demonstrates the role of bottom currents in the shaping of the slope. The enlargement of canyons and the change in the course when they cross the border fault imply that tectonic has also influenced in the morphology of deep waters environments of Potiguar Basin. The current sedimentation of continental slope is considered mixed because the sediments are composed of siliciclastics and bioclasts. Predominant siliciclastics are calcite, dolomite, quartz, and clay minerals. The presence of stable minerals (zircon, tourmaline and rutile), and fragmented bioclasts implies the contributions of Rivers A?u and Apodi / Esta disserta??o apresenta os resultados do primeiro imageamento realizado no talude continental, em ?rea adjacente ? Bacia Potiguar, na margem equatorial brasileira (NE Brasil). Dados de batimetria multifeixe forneceram uma cobertura completa do fundo oce?nico entre o talude superior e o talude intermedi?rio (100-1300 m). Quinze canyons submarinos foram mapeados. A forma do talude reflete na distinta distribui??o espacial dos canyons. A parte oeste apresenta perfis convexos o que implicou numa maior quantidade de incis?es pelos canyons. Alguns deles possuem paredes com declividades maiores que 35?. Os canyons foram classificados de acordo com sua localiza??o e morfologia. Os canyons com cabeceiras entalhadas na plataforma, conex?o com sistemas fluviais, altas sinuosidades, formas em V , terra?os ao longo das margens e com fei??es erosivas como ravinas permitem deduzir uma sedimenta??o areno-cascalhosa. Estes canyons s?o associados ? deposi??o de sistemas de leques submarinos que t?m sido considerados reservat?rios de hidrocarbonetos. A presen?a de ravinas, ranhuras e dunas demonstram o papel das correntes de fundo na forma do talude. Os alargamentos dos canyons e a mudan?a na dire??o do curso onde cruzam a falha de borda da bacia implicam que a tect?nica tamb?m influencia na morfologia dos ambientes profundos da Bacia Potiguar. A sedimenta??o atual do talude continental ? considerada mista, pois os sedimentos possuem componentes silicicl?sticos e biocl?sticos. Dentre os silicicl?sticos destacam-se calcita, dolomita, quartzo e os argilominerais. A presen?a de alguns minerais pesados tais como zirc?o, turmalina e rutilo, bem como biocl?sticos fragmentados, indicam a maturidade dos sedimentos e a contribui??o dos Rios A?u e Apodi para os sedimentos da ?rea de estudo

This study uses a new integrated outcrop data and airborne lidar from Slaughter Canyon, New Mexico, to quantitatively characterize the cycle-scale facies architecture within the G23-G26 high frequency sequences of the Yates Formation. High frequency cycle-scale mapping of these sequences shows sedimentological evidence for accommodation reduction associated with the Permain composite sequence (CS) 13 highstand (G23-G25). Development of the G26 HFS additionally demonstrates the isochronous balance of mixed carbonate-siliciclastic deposition across the Yates-Capitan reef-rimmed shelf during the initial CS-scale transgression following significant exposure and bypass of sand across the shelf. This sequence framework is quantitatively analyzed using progradation to aggradation (P/A) ratios, facies proportions, facies tract dip width, and facies tract bedding angles to evaluate the interplay of eustacy and syndepositional deformation as drivers of stratigraphic architecture. The sequences defined here developed in response to both eustacy and syndepositional deformation, but individual facies distributions and cycle stacking patterns were largely controlled by eustacy; while facies, cycle, and sequence thicknesses as well as facies bedding angles were locally influenced by syndepositional faulting. A reconstruction of each high frequency sequence and stepwise documentation of post-depositional fault displacement and HFS basinward rotation was generated using the lidar data. This analysis shows that the G23-G26 HFS developed basinward-dipping depositional topography from the shelf crest to the shelf margin reef. This geometry was largely unaltered by syndepositional faults during individual HFS deposition, but was rotated basinward shortly thereafter by younger fault movement. The accommodation trends recorded in this largely shelf crest to shelf margin window can be additionally projected into the middle shelf producing zones of the prolific Yates-aged reservoirs on the Northwest Shelf and Central Basin Platform. / text

Cette étude porte sur l’analyse des séries jurassiques du Shaqra Group (Toarcian to Kimmeridgian) qui affleurent de manière continue en Arabie centrale le long d’un transect de plus de 1000 km de long. Ces séries se sont accumulées sur une vaste plate-forme épicontinentale peu profonde, en contexte tropical. Ces affleurements permettent ainsi d’observer la partie occidentale des séries renfermant des systèmes pétroliers prolifiques exploités en subsurface en Arabie Saoudite. L’analyse sédimentologique de nombreuses coupes et la réalisation de corrélations stratigraphiques de haute résolution sur un transect de 600 km au sud de Riyad, complété par des corrélations avec les données de forage plus à l’est (entre Riyadh et le Rimthan Arch), permettent de distinguer une organisation séquentielle à différents ordres de fréquence et de reconstituer l’évolution de la plate-forme au sein de ces séquences. La plate-forme jurassique évolue d’une plate-forme horizontale caractérisée par des systèmes mixtes à la transition continental-marin du Toarcien au Callovien moyen (formations Marrat et Dhruma) vers un système de type rampe - bassin intrashelf du Callovien au Kimméridgien inférieur (formations Tuwaiq et Hanifa) pour finir par une plate-forme aggradante carbonatée et silico-clastique (Fm. Jubaila) puis carbonatée et évaporitique en contexte aride (Fm. Arab) au Kimméridgien. Les cycles tectono-stratigraphiques de 2ème ordre du Jurassique inférieur et moyen sont limités à la base et au sommet par des discontinuités régionales. Ils occupent un dépôt-centre stationnaire et décrivent un onlap côtier de grande ampleur avec un maximum transgressif au Callovien moyen (Upper Tuwaiq Mb.). Durant le Jurassique supérieur, les dépôts de rampe carbonatée de la Formation Hanifa passent progressivement vers l’ouest à des dépôts plus profonds de bassin intrashelf relativement riches en matière organique (Khurais - Rimthan Arch). La séquence Jubaila – Arab-D montre des variations d’épaisseur qui indiquent une déformation de grande longueur d’onde de la plate-forme arabe à cette période. Les faciès récifaux du membre Arab D sont interprétés comme représentant le maximum d’inondation de ce cycle qui se termine par le développement de systèmes carbonatés – évaporitiques à la fin du Jurassique. / They serve as westernmost reference for adjacent prolific reservoirs and source-rock bearing intrashelf basins. Several hierarchical sequences (second to fourth order) have been recognized in outcrops sections (600 km long south of Riyadh) and correlated with gamma-ray logs of subsurface wells (550 km long from Riyadh to Rimthan Arch). The Jurassic platform evolved from very-flat continental-to-nearshore mixed carbonate-siliciclastic platform (Marrat-Dhruma; Toarcian to Middle Callovian) to differentiated ramp with deep intrashelf basins (Tuwaiq-Hanifa; Callovian to Early Kimmeridgian) to a lowstand followed by flat aggraded platform (Jubaila-Arab-D; Kimmeridgian). Tectonic related siliciclastic influx took place in arid condition during the Kimmeridgian (Jubaila Fm.). The Jurassic platform ends with the mixed carbonate-evaporite systems of the Arab Fm. A first second-order tectono-eustatic cycle (Marrat to Tuwaiq) is bounded at the base and top by regional unconformities. It has a stationary depocenter, and show long-term coastal onlap and marine transgression that reached its maximum extent during the upper Tuwaiq (Middle Callovian). The Hanifa Fm. consists of four 3rd-order sequences aggraded flat-toped platform (outcrops to Khurais) marked at the base by argillaceous limestone and top by pure high-energy carbonates with localized reef buildups. The Jubaila Arab-D is two 3rd-order sequences begin with low-stand deposits followed by long-term transgression. These formed flat successions with lateral thickness variations controlled by differential subsidence increased in the Arabian Basin. The transgression is marked by storm-influenced inner-platform with sandstone quartz, grainstones and restricted lime-mudstone. The Maximum marine transgression is placed in the Arab-D with reef buildups in the westernmost inner-platform. During highstand, the reefs are gently prograding out into Rimthan Arch leaving behind restricted lagoon and sabkhah/salina anhydrite.

L’étude de l’Ordovicien de l’Anti-Atlas oriental s’intègre dans un vaste projet celui de l’étude de la plate-forme nord-gondwanienne qui se caractérise par une sédimentation essentiellement silico-clastique avec une polarité globale qui est Sud-Nord. Cette étude, basée sur les principes de la stratigraphie séquentielle et de la sédimentologie, met en évidence l’existence de deux systèmes de dépôts sur la marge nord-ouest de la plate-forme nord-gondwanienne. A l’Ordovicien moyen et supérieur préglaciaire, à l’emplacement de l’Anti-Atlas oriental, coexistent un système deltaïque (lato sensu) et un système de plate-forme dominée par l’action de la houle et des tempêtes. Ces deux systèmes de dépôts ont une certaine répartition spatiale et temporelle. Le système deltaïque domine le nord-est de l’Anti-Atlas oriental où il prend naissance à l’Est du Tafilalt. Ce système deltaïque est à dominance fluviale, il est actif lors des périodes de régression. Pendant les maximums de régression, il incise le haut du plateau continental en créant d’importantes structures érosives dont le remplissage se fait par des faciès de haute énergie à composante unidirectionnelle. Le système de haute énergie influencé par l’action de la houle et des tempêtes domine le secteur sud de l’Anti-Atlas oriental et se répand au nord au cours des périodes transgressives. La sédimentation durant l’Ordovicien préglaciaire sur la marge nord-ouest du Gondwana a un contrôle tectonique et eustatique avec une polarité des systèmes, dans le Tafilalt-Maïder qui diffère de celle de la plate-forme nord-gondwanienne et est Nord Est-Sud-Ouest. Le profil de dépôt est quasi plat où les clinoformes sont de faible amplitudes et se dessinent à l’intérieur des séquences de 3ème ordre. Le Darriwillien se caractérise par des une subsidence différentielle entre le domaine nord et le domaine sud en raison d’une tectonique active. Alors que, le Sandbien-Katien montre un taux de subsidence faible (x 10m/Ma) en adéquation avec un contexte intracratonique. L’Hirnantien dans le Tafilalt, décrit comme étant discontinu voir absent, est très bien développé il se caractérise par la mise en place d’une sédimentation mixte gréso-carbonaté à bryozoaires de type littoral et ce à l’extrémité oriental de l’Anti-Atlas et d’une épaisse série conglomératique (conglomérat d’Amessoui et d’Imzizoui) et flyschoïde qui peut atteindre les 500m dans le Tafilalt. / The Ordovician Anti-Atlas study is part of a larger project of comprehension the sedimentary system of the north Gondwana platform. This sedimentary area is characterized by essentially terrigenous sediments that come from the south from de West African Craton. This study based on sequence stratigraphy and sedimentology principles highlights two systems juxtaposed during the preglacial Ordovician period (before hirnantian). These two deposits systems have a spatial and temporal distribution. One deltaic occurs on north-eastern Tafilalt (east Anti-Atlas) and widespread during regressive periods. The second is storm dominate system which is developed in the south-western part of eastern Anti-Atlas and transgressive periods. The deltaic system is river dominant, it incise the continental shelf by creating a significant erosive structure whose filling is done by high energy facies unidirectional component. During the Ordovician, the sedimentation was controlled by tectonic and eustatic variation. The polarity of the system in the Tafilalt-Maïder is different from that of the northern Gondwana platform and it is given North East- South West. The Darriwilian characterized by differential subsidence, between the north and the south of the oriental Anti-Atlas, due to active tectonics, while, Sandbian-Katian show a low subsidence rates (x10m/Ma) in the line of intracratonic basin. The Hirnantian, in Tafilalt, is largely well developed and characterized by huge conglomeratic series, flysch deposits and Bryozoan limestone at the northeastern.