Well-preserved echinoderm faunas are rare in the fossil record, and when uncovered, understanding their occurrence can be useful in interpreting other faunas. In this study, two such faunas of the same age from separate localities in the shallow-marine Ramey Creek Member of the Slade Formation in the Upper Mississippian (Chesterian) rocks of eastern Kentucky are examined. Of the more than 5,000 fossil specimens from both localities, only 9–34 percent were echinoderms from 3–5 classes. Nine non-echinoderm (8 invertebrate and one vertebrate) classes occurred at both localities, but of these, bryozoans, brachiopods and sponges dominated. To understand the attributes of both localities (Valley Stone and 213 quarries), the geologic and structural settings, lithofacies and depositional environments, as well as faunal makeup and abundances (diversity, evenness, density), were compared and contrasted. Faunas from the Valley Stone Quarry were located on an uplifted fault block in more shallow, open-marine waters with higher energies. As indicated by four distinct lithofacies, the depositional setting was more extensive and varied with interspersed shoals and basins that could accommodate a greater richness (65 species), even though organism densities and abundance were less. In contrast, fauna from the 213 Quarry were located on a downdropped fault block in a more localized, deeper, storm-shelf setting, characterized by a single lithofacies. Although organism density and abundance were nearly twice as high as that at the Valley Stone Quarry, species richness was lower (45 species), and only one species, a bryozoan, predominated. Overall, echinoderm classes, species and individuals were more abundant at the Valley Stone Quarry, and I suggest that this is related to the shallower and more varied depositional environments that developed in response to presence on the shallow, uplifted fault block. This suggests the importance of regional features like faults in controlling environments and organism distribution through time. Although the faunas were originally collected for their echinoderm-dominated “crinoid gardens,” in fact, echinoderms were in the minority, and bryozoans and brachiopods predominated in the communities. Hence, the communities might better be described as bryozoan “thickets” and brachiopod “pavements.”

A study of a 250 ft. (76.2 m) stratigraphic interval that includes the Eocene-age Felix coal of the Wasatch Formation was undertaken in the Powder River Basin of Wyoming to establish a depositional model based on the interrelations of coal-seam geometry, coal maceral composition, and spatial distribution of adjoining rocks. Regional cross sections and maps of major rock bodies were prepared from 147 measured stratigraphic sections and 56 geophysical logs. Trends in maceral and chemical properties within the Felix coal were identified from petrographic and geochemical analyses of 72 coal channel samples. The combined data sets indicate that the thickest portions of the coal are underlain by widespread, interconnected, sandstone-dominated fining-upward sequences (< 50 ft. or 15 m thick over a 300 sq. mi. or 777 sq. km area) whereas areas of thin or split coal are underlain by stacked predominantly fine grained, coarsening-upward sequences (< 50 ft. or 15 m thick). Above the coal, fining-upward sequences are concentrated over thin coal areas and widespread (> 20 mi., 32 km wide) coarsening-upward sequences overlie thick coal areas. Megascopic and petrographic description of the coal indicates that the brightest coal contains the greatest amount of huminite. This type coal occurs in the lowest portion of the seam and directly above clay partings in thick coal areas and in split benches · on the margin of the deposit. The central and upper portion of the seam is predominantly dull, and inertinite percentages increase towards the top of the seam. The deposits below the Felix resulted from north-northwest flowing meandering rivers. Thick peat represented by thick portions of the Felix coal accumulated upon this sandstone-dominated, poorly compactible platform that was free of sediment influx. Areas of thin and split Felix coal, underlain by fine-grained, more-compactible sediments, attracted water-borne elastics that interrupted peat accumulation. The base and split portions of the seam are the remains of predominantly coniferous trees that grew within a nutrient-rich environment, and the duller central and upper portions of the seam indicate oxidation associated with a raised peat deposit. Ash falls and fires during late stages of peat accumulation may have contributed to the demise of the swamp. After vegetation died large lakes formed and were subsequently filled by crevasse deposits from streams. The final phase of compaction of the fine-grained lake sediments and the thick underlying peat attracted anastomosed alluvial channels.

A chronostratigraphic subdivision of the Upper Jurassic synrift sediments in the eastern Barrow Sub-basin was developed from the integration of core logging, petrography, well log sequence analyses and seismic stratigraphy. From this basis, the Callovian to base Cretaceous sediments may be subdivided into five depositional sequences. The development of the sequence boundaries, in most part, is closely related to periods of major changes in basin configuration associated with the sequential breakup of eastern Gondwanaland. Initiation of the Upper Jurassic rift complex occurred during late Callovian early Oxfordian associated with the development of a northeast-southwest trending spreading centre on the Argo Abyssal Plain. The spreading centre propagated southwards during the Late Jurassic. This resulted in active rifting in the Barrow Sub-basin and ultimately led to the separation of the Indian and Australian plates during Valanginian time.Upper Jurassic synrift sediments in the eastern Barrow Sub-basin consist of detached basin floor fan complexes, channelised and canyon fed fan systems, slump deposits, prograding outer shelfal to slope deposits and deep marine claystones. Post-depositional uplift of the eastern shelfal areas during the Late Jurassic resulted in erosion of the transgressive and highstand fluvial-deltaic to shelfal deposits. These periods of uplift and erosion provided much of the sediment redeposited in the basinal areas during the lowstand periods. Seven sandstone facies were recognised in the Upper Jurassic sedimentary section based on core control. Each sandstone has unique reservoir characteristics which can be related to the depositional setting. / The abundance of glauconite and belemnites combined with ichnology and biostratigraphic assemblages associated with marine environments, indicate that deposition of all the sandstone facies occurred within an outer shelfal - deep marine environment. Reservoir quality was best developed in the dominantly medium grained, moderate - well sorted sandstones, (facies 7), which were deposited as detached, basin floor submarine fan sands or interbedded turbidites. In contrast, reservoir quality was relatively poorly developed in the remaining facies which were deposited as slope fans, slumps, or distal turbidite deposits.The abundance of quartz and presence of banded iron, jasper, and potassic feldspar grains support the provenance for the basinal sandstone facies being the Precambrian alkyl granites and banded iron formation of.the Pilbara Shield and Hammersley Ranges. These Precambrian igneous rocks and metasediments mark the eastern boundary of the Barrow Sub-basin study area. To predict the distribution of sedimentary facies in the Upper Jurassic synrift sediments of the eastern Barrow Sub-basin, the interplay between the major controlling depositional processes, namely tectonics, sediment supply and eustasy must be understood. Subdivision of the synrift sedimentary section on the basis of lithostratigraphy can be misleading and does not adequately resolve the facies relationships observed in the well intersection. The results of this research form the basis for a regional sequence analysis and seismic stratigraphic study.

A study of the distribution of diagenetic alterations and their impact on reservoir-quality evolution in four deep-water turbidite successions (Cretaceous to Eocene) from basins in active (foreland) and passive margins revealed the impact of tectonic setting, depositional facies, and changes in the relative sea level. Diagenetic modifications encountered in the turbiditic sandstones from the passive margin basins include dissolution and kaolinitization (kaolin has δ18OV-SMOW = +13.3‰ to +15.2‰; δDV-SMOW = -96.6‰ to -79.6‰) of framework silicates, formation of grain coating chloritic and illitic clays, cementation by carbonates and quartz, as well as the mechanical and chemical compaction of detrital quartz. Kaolinitization, which is most extensive in the lowstand systems tracts, is attributed to meteoric-water flux during major fall in the relative sea level. Preservation of porosity and permeability in sandstones from the passive margin basins (up to 30% and 1 Darcy, respectively) is attributed to the presence of abundant rigid quartz and feldspar grains and to dissolution of carbonate cement as well as mica and feldspars. Diagenetic modifications in turbidites from the foreland basins include carbonate cementation and mechanical compaction of the abundant ductile rock fragments, which were derived from fold-thrust belts. These diagenetic alterations resulted in nearly total elimination of depositional porosity and permeability. The wide range of δ13CV−PDB values of these cements (about -18‰ to +22‰) in passive margin basins is attributed to input of dissolved carbon from various processes of organic matter alterations, including microbial methanogenesis and thermal decarboxylation of kerogen. The narrower range of δ13CV−PDB values of these cements (about -2‰ to +7‰) in the foreland basins suggests the importance of carbon derivation from the dissolution of carbonate grains. The generally wide range of δ18O values (about -17‰ to -1‰) of the carbonate cements reflect the impact of oxygen isotopic composition of the various fluid involved (including marine depositional waters, fluxed meteoric waters, evolved formation waters) and the wide ranges of precipitation temperatures. Results of this study are anticipated to have important implication for hydrocarbon exploration in deep-water turbidites from passive and active margin basins and for pre-drilling assessment of the spatial and temporal distribution of reservoir quality in such deposits.

A Formação Tacuarembó (Jurássico Superior – Cretáceo Inferior), subdividida em Membro Batoví e Membro Rivera, aflora na região norte do Uruguai, nos departamentos de Rivera e Tacuarembó. O objetivo principal deste trabalho é a análise sedimentológica e estratigráfi-ca da Formação Tacuarembó, através da caracterização faciológica, a reconstrução dos modelos deposicionais e a definição das relações de contato entre os membros Batoví e Rivera. Para alcançar tal objetivo, foi realizado o levantamento, na escala 1:50, de um tes-temunho e de quarenta e uma seções colunares, estas divididas em sete transectas com base em sua distribuição espacial. Como resultado, foram detalhadas litofácies posterior-mente agrupadas em diferentes associações de fácies. O Membro Batoví é constituído por associações de fácies de (1) dunas eólicas, (2) lençóis de areia eólicos, (3) canais fluviais efêmeros, (4) canais fluviais perenes entrelaçados e (5) deltas. O Membro Rivera, por sua vez, é constituído essencialmente por associações de fácies de dunas eólicas. A intercala-ção entre depósitos fluviais, eólicos e deltaicos, com predominância de associações fluviais sugere que o Membro Batoví representa o modelo deposicional de porção distal de um sis-tema fluvial distributário Já o Membro Rivera caracteriza-se pelo sucessivo cavalgamento de dunas eólicas, sem a ocorrência de depósitos de interdunas úmidas ou encharcadas, definindo um sistema eólico seco. A mudança abrupta de sistemas deposicionais, marcada por uma superfície plana, por vezes com concentração de clastos, indica a existência de uma discordância entre os membros Batoví e Rivera. Aliado a isto, a mudança no modelo deposicional sugere uma alteração climática, passando de um clima arido a semi-árido du-rante a deposição do Membro Batoví, para um clima hiperárido ao longo da deposição do Membro Rivera. / The Tacuarembó Formation (Upper Jurassic - Lower Cretaceous), subdivided into Batoví Member and Rivera Member, crops in the northern region of Uruguay, in the Rivera and Tacuarembó departments. The main objective of the present work is the sedimentological and estratigraphic analysis of the Tacuarembó Formation, through the faciological charac-terization, reconstruction of the depositional models and definition of contact relations be-tween the Batoví and Rivera members. To reach such objective, a well-log and forty-one columnar sections were surveyed in a scale 1:50, and later the columnar sections were di-vided into seven transects, based on their spatial position. As a result, lithofacies were de-tailed and later grouped in different facies associations.The Batoví Member consists of associations of facies of (1) eolian dunes, (2) eolian sand sheets, (3) ephemeral fluvial channels, (4) perennial braided fluvial channels and (5) deltaic. On the other hand, the Ri-vera Member, is essentially constituted by facies associations eolian dunes. The intercala-tion between fluvial, eolian and deltaic deposits, with predominance of fluvial associations, suggests that the Batoví Member represents the depositional model of the distal portion of a distributary fluvial system. Contrastingly, the Rivera Member is characterized by the suc-cessive eolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry eolian system. The abrupt change of depositional systems, marked by a flat surface, sometimes with clasts concentration, indicates the existence of an unconformity between the members Batoví and Rivera. Allied to this, the change in the depositional model suggests a climatic change, going from arid to semi-arid climate during the deposi-tion of the Batoví Member, to a hyperarid climate during the deposition of the Rivera Mem-ber.

Os sistemas eólicos foram abundantes e muito comuns no início da Era Proterozoica Era, depois de 2.2 Ga. No entanto, a maioria das sucessões eólicas dessa idade são intensamente deformadas e fragmentadas, o que implica que até o momento, poucas tentativas foram feitas para aplicar uma abordagem de estratigrafia de sequências, para determinar os mecanismos de construção, acumulação e preservação das sequências eólicas, da mesma forma, não existem trabalhos realizados até o presente momento que utilizem os registros de acumulação eólica e reconstruções paleogeográficas para modelar a circulação atmosférica do Pré- Cambriano. A Formação Mangabeira é uma sucessão eólica de idade Mesoproterozóica bem preservada no Cráton do São Francisco, nordeste do Brasil. Duas unidades principais foram identificadas com base na arquitetura deposicional e na análise dos paleoventos. A unidade inferior da Formação Mangabeira (~ 500 m de espessura) compreende depósitos eólicos de duna, interdunas, lençóis de areia eólicos, assim como depósitos fluviais. Estes depósitos são organizados em ciclos sedimentares que se sucedem verticalmente, cada ciclo com 6 a 20 m de espessura, caracterizados por lençóis de areia eólicos e depósitos fluviais que são substituídos por dunas eólicas e depósitos interdunas indicando uma tendência de ressecamento para o topo. Os dados de paleoventos indicam um transporte atual dominantemente à norte. Estes ciclos surgem em resposta a oscilações climáticas de um clima relativamente úmido para condições climáticas áridas possivelmente relacionadas com forças orbitais. O limite entre a Unidade Inferior e a Unidade Superior sobrejacente é marcado por uma mudança na arquitetura deposicional e uma mudança brusca no padrão de paleoventos. A Unidade Superior (200 m de espessura) é caracterizada por sucessivos sets de estratos cruzados simples, cada set com ~ 3 a 10 m de espessura, que indicam a migração e acumulação de grandes dunas eólicas sem regiões de interdunas, e que se acumulou como um sistema eólico seco. Os dados de paleoventos indicam transporte atual predominantemente ao sul. Esta sucessão se acumulou durante um episódio de longa duração de hiperaridez. Localmente, a Unidade Superior inclui depósitos fluviais menores que registram um evento úmido de curta duração, ou uma inundação rara por sistemas fluviais provenientes das margens da bacia. A combinação dos dados de paleoventos com mapas paleogeográficos demonstra uma boa correlação entre a circulação atmosférica e distribuição das massas de terras. Entre 1,6-1,54 Ga o Cráton São Francisco estava localizado entre as latitudes médias e o equador. Os registros do regime de vento a partir dos estratos cruzados da Unidade Inferior são consistentes com as posições paleogeográficas do Cráton do São Francisco entre 25º a 35º S, prevalecendo um padrão de vento zonal. Entre 1,54-1,5 Ga a grande massa de terra (cratons do São-Francisco, Congo e Sibéria) derivou mais ao norte atingindo paleolatitudes entre 30º S e 30ºN. Nessa altura, o Cráton do São Francisco estava posicionado na zona equatorial. Esta paleogeografia é consistente com os paleoventos registrados na Unidade Superior, dominando um padrão de vento de monções. / Aeolian systems were abundant and widespread in the early Proterozoic Era, after 2.2 Ga. However, the majority of aeolian successions of such great age are intensely deformed and are preserved only in a fragmentary state meaning that, hitherto, few attempts have been made to apply a sequence stratigraphic approach to determine mechanisms of aeolian construction, accumulation and preservation in such systems, as the same way, no attempts to use the records of aeolian accumulation and palaeogeographic reconstructions of the land mass distribution to model Precambrian atmospheric circulation have been undertaken so far. The Mangabeira Formation is a well preserved Mesoproterozoic erg succession covering part of the São Francisco Craton, northeastern Brazil. Two main units are identified based on stratigraphic architecture and analysis of regional palaeo-sand transport directions. The lower unit of the Mangabeira Formation (~500 m thick) comprises aeolian deposits of dune, interdune, and sand-sheet origin, as well as some of water-lain origin. These deposits are organized into vertically stacked depositional cycles, each 6 to 20 m thick and characterized by aeolian sandsheet and water-lain deposits succeeded by aeolian dune and interdune deposits indicative of a drying-upward trend. Palaeocurrent data indicate aeolian sand transport dominantly to the presentday north. These cycles likely arose in response to climatic oscillations from relatively humid to arid conditions, possibly related to orbital forcing. The boundary between this lower unit and an overlying upper unit is an unconformity of regional extent marked by a change in the depositional architecture and an abrupt shift in palaeocurrent pattern. The Upper Unit (200 m thick) is characterized by stacked sets of simple cross strata, each ~3 to 10 m thick, which are indicative of the migration and accumulation of large aeolian dunes that lacked interdune flats of appreciable size, and which accumulated as a dry aeolian system. Palaeocurrent data indicates aeolian sand transport dominantly to the present-day south. This succession is interpreted to have accumulated during a long-lived episode of hyper-aridity. Locally, the upper unit includes minor fluvial deposits that may record a short-lived event of heightened humidity, or a rare flood event by fluvial systems sourced from the basin margin. The combination of the palaeowinds data with 1.6 - 1.5 Ga palaeogeographic maps demonstrate a good correlation between atmospheric circulation and land mass distribution. At 1.6 to 1.54 Ga São Francisco Craton has been located between mid-latitudes and equatorial zone. The wind regime records from the cross-strata of the Lower Unit are consistent with the palaeogeographic positions of São Francisco between 25º to 35º S, prevail a zonal wind pattern. At 1.54 to 1.5 Ga the large land mass (São-Francisco-Congo and Siberian cratons) drifted farther north reaching palaeolatitudes between 30º S and 30ºN. At that time the São Francisco Craton has been located in the equatorial zone. This palaeogeography is consistent with the northwestern palaeowinds directions recorded in the Upper Unit which dominates a monsoonal wind pattern.

Made available in DSpace on 2014-06-11T19:26:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-18Bitstream added on 2014-06-13T20:54:16Z : No. of bitstreams: 1 zani_h_me_rcla.pdf: 8429664 bytes, checksum: 62c5b99b684e6da2a2faa22d20ae412e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Esta dissertação visa caracterizar mudanças morfológicas recentes no megaleque do Taquari, através de dados de Sensoriamento Remoto. As baixas declividades do terreno e pequenas amplitudes das formas deposicionais, que predominam nesta paisagem, demandaram o desenvolvimento de métodos específicos para a extração das informações. Dados SRTM e imagens multiespectrais foram utilizados no mapeamento dos paleocanais e confecção de modelos digitais de elevação. A drenagem relicta foi mapeada através de desenho digital, sobre mosaicos georreferenciados dos sensores ASTER, MODIS e CBERS2. Nos vetores dos paleocanais identificados foi realizado cálculo de densidade areal e criados histogramas direcionais (rosetas), que ressaltaram relações topológicas e permitiram a interpretação de seis lobos deposicionais. Modelos digitais de elevação foram gerados através da subtração dos dados SRTM originais com uma superfície topográfica simplificada pelo método de regressão polinomial cúbica. Este processamento ressaltou zonas deprimidas no megaleque, espaços potenciais para acúmulo de sedimentos, e zonas de sobrelevadas, devido à processos agradacionais contínuos em determinadas áreas. A identificação e caracterização destas formas é passo inicial para a reconstituição dos eventos geomórficos e antevisão de futuras mudanças no curso do rio Taquari. A dinâmica de construção e abandono dos lobos mostrou-se mais complexa do que o apresentado em trabalhos anteriores, sendo de aspecto fragmentado e de natureza fractal. / This work aims characterize morphological changes in Taquari megafan, by remote sensing techniques. Gentle slopes of landscape and low amplitudes of geoforms demands the development of specific methods to extract valuable topographic information. SRTM data and multispectral images were used to map paleochannels and to build digital elevation models (DEM). Relict streams were mapped by computer-aided design in GIS environment, using georeferenced mosaics of ASTER, CBERS and MODIS sensors. These vectors were used to calculate drainage density and directional histograms, revealing topological aspects and lead to interpret 6 depositional lobes. DEM was obtained by subtracting the original SRTM data from a simplified surface generated by cubic polynomial regression. This product revealed depressed areas in the Taquari megafan, potential accommodation spaces for deposition, and geoforms with a higher amplitude than their neighbor, probably because of continuous gradational processes in these specifics sites. The recognition of these landforms is the initial step for figure out the evolution of geomorphic events and to support a well done planning in land occupation. The dynamics of Taquari megafan showed to be more complex than previous studies proposed.

A Formação Tacuarembó (Jurássico Superior – Cretáceo Inferior), subdividida em Membro Batoví e Membro Rivera, aflora na região norte do Uruguai, nos departamentos de Rivera e Tacuarembó. O objetivo principal deste trabalho é a análise sedimentológica e estratigráfi-ca da Formação Tacuarembó, através da caracterização faciológica, a reconstrução dos modelos deposicionais e a definição das relações de contato entre os membros Batoví e Rivera. Para alcançar tal objetivo, foi realizado o levantamento, na escala 1:50, de um tes-temunho e de quarenta e uma seções colunares, estas divididas em sete transectas com base em sua distribuição espacial. Como resultado, foram detalhadas litofácies posterior-mente agrupadas em diferentes associações de fácies. O Membro Batoví é constituído por associações de fácies de (1) dunas eólicas, (2) lençóis de areia eólicos, (3) canais fluviais efêmeros, (4) canais fluviais perenes entrelaçados e (5) deltas. O Membro Rivera, por sua vez, é constituído essencialmente por associações de fácies de dunas eólicas. A intercala-ção entre depósitos fluviais, eólicos e deltaicos, com predominância de associações fluviais sugere que o Membro Batoví representa o modelo deposicional de porção distal de um sis-tema fluvial distributário Já o Membro Rivera caracteriza-se pelo sucessivo cavalgamento de dunas eólicas, sem a ocorrência de depósitos de interdunas úmidas ou encharcadas, definindo um sistema eólico seco. A mudança abrupta de sistemas deposicionais, marcada por uma superfície plana, por vezes com concentração de clastos, indica a existência de uma discordância entre os membros Batoví e Rivera. Aliado a isto, a mudança no modelo deposicional sugere uma alteração climática, passando de um clima arido a semi-árido du-rante a deposição do Membro Batoví, para um clima hiperárido ao longo da deposição do Membro Rivera. / The Tacuarembó Formation (Upper Jurassic - Lower Cretaceous), subdivided into Batoví Member and Rivera Member, crops in the northern region of Uruguay, in the Rivera and Tacuarembó departments. The main objective of the present work is the sedimentological and estratigraphic analysis of the Tacuarembó Formation, through the faciological charac-terization, reconstruction of the depositional models and definition of contact relations be-tween the Batoví and Rivera members. To reach such objective, a well-log and forty-one columnar sections were surveyed in a scale 1:50, and later the columnar sections were di-vided into seven transects, based on their spatial position. As a result, lithofacies were de-tailed and later grouped in different facies associations.The Batoví Member consists of associations of facies of (1) eolian dunes, (2) eolian sand sheets, (3) ephemeral fluvial channels, (4) perennial braided fluvial channels and (5) deltaic. On the other hand, the Ri-vera Member, is essentially constituted by facies associations eolian dunes. The intercala-tion between fluvial, eolian and deltaic deposits, with predominance of fluvial associations, suggests that the Batoví Member represents the depositional model of the distal portion of a distributary fluvial system. Contrastingly, the Rivera Member is characterized by the suc-cessive eolian dunes climbing, without the occurrence of wet or damp interdunes deposits, defining a dry eolian system. The abrupt change of depositional systems, marked by a flat surface, sometimes with clasts concentration, indicates the existence of an unconformity between the members Batoví and Rivera. Allied to this, the change in the depositional model suggests a climatic change, going from arid to semi-arid climate during the deposi-tion of the Batoví Member, to a hyperarid climate during the deposition of the Rivera Mem-ber.

Os sistemas eólicos foram abundantes e muito comuns no início da Era Proterozoica Era, depois de 2.2 Ga. No entanto, a maioria das sucessões eólicas dessa idade são intensamente deformadas e fragmentadas, o que implica que até o momento, poucas tentativas foram feitas para aplicar uma abordagem de estratigrafia de sequências, para determinar os mecanismos de construção, acumulação e preservação das sequências eólicas, da mesma forma, não existem trabalhos realizados até o presente momento que utilizem os registros de acumulação eólica e reconstruções paleogeográficas para modelar a circulação atmosférica do Pré- Cambriano. A Formação Mangabeira é uma sucessão eólica de idade Mesoproterozóica bem preservada no Cráton do São Francisco, nordeste do Brasil. Duas unidades principais foram identificadas com base na arquitetura deposicional e na análise dos paleoventos. A unidade inferior da Formação Mangabeira (~ 500 m de espessura) compreende depósitos eólicos de duna, interdunas, lençóis de areia eólicos, assim como depósitos fluviais. Estes depósitos são organizados em ciclos sedimentares que se sucedem verticalmente, cada ciclo com 6 a 20 m de espessura, caracterizados por lençóis de areia eólicos e depósitos fluviais que são substituídos por dunas eólicas e depósitos interdunas indicando uma tendência de ressecamento para o topo. Os dados de paleoventos indicam um transporte atual dominantemente à norte. Estes ciclos surgem em resposta a oscilações climáticas de um clima relativamente úmido para condições climáticas áridas possivelmente relacionadas com forças orbitais. O limite entre a Unidade Inferior e a Unidade Superior sobrejacente é marcado por uma mudança na arquitetura deposicional e uma mudança brusca no padrão de paleoventos. A Unidade Superior (200 m de espessura) é caracterizada por sucessivos sets de estratos cruzados simples, cada set com ~ 3 a 10 m de espessura, que indicam a migração e acumulação de grandes dunas eólicas sem regiões de interdunas, e que se acumulou como um sistema eólico seco. Os dados de paleoventos indicam transporte atual predominantemente ao sul. Esta sucessão se acumulou durante um episódio de longa duração de hiperaridez. Localmente, a Unidade Superior inclui depósitos fluviais menores que registram um evento úmido de curta duração, ou uma inundação rara por sistemas fluviais provenientes das margens da bacia. A combinação dos dados de paleoventos com mapas paleogeográficos demonstra uma boa correlação entre a circulação atmosférica e distribuição das massas de terras. Entre 1,6-1,54 Ga o Cráton São Francisco estava localizado entre as latitudes médias e o equador. Os registros do regime de vento a partir dos estratos cruzados da Unidade Inferior são consistentes com as posições paleogeográficas do Cráton do São Francisco entre 25º a 35º S, prevalecendo um padrão de vento zonal. Entre 1,54-1,5 Ga a grande massa de terra (cratons do São-Francisco, Congo e Sibéria) derivou mais ao norte atingindo paleolatitudes entre 30º S e 30ºN. Nessa altura, o Cráton do São Francisco estava posicionado na zona equatorial. Esta paleogeografia é consistente com os paleoventos registrados na Unidade Superior, dominando um padrão de vento de monções. / Aeolian systems were abundant and widespread in the early Proterozoic Era, after 2.2 Ga. However, the majority of aeolian successions of such great age are intensely deformed and are preserved only in a fragmentary state meaning that, hitherto, few attempts have been made to apply a sequence stratigraphic approach to determine mechanisms of aeolian construction, accumulation and preservation in such systems, as the same way, no attempts to use the records of aeolian accumulation and palaeogeographic reconstructions of the land mass distribution to model Precambrian atmospheric circulation have been undertaken so far. The Mangabeira Formation is a well preserved Mesoproterozoic erg succession covering part of the São Francisco Craton, northeastern Brazil. Two main units are identified based on stratigraphic architecture and analysis of regional palaeo-sand transport directions. The lower unit of the Mangabeira Formation (~500 m thick) comprises aeolian deposits of dune, interdune, and sand-sheet origin, as well as some of water-lain origin. These deposits are organized into vertically stacked depositional cycles, each 6 to 20 m thick and characterized by aeolian sandsheet and water-lain deposits succeeded by aeolian dune and interdune deposits indicative of a drying-upward trend. Palaeocurrent data indicate aeolian sand transport dominantly to the presentday north. These cycles likely arose in response to climatic oscillations from relatively humid to arid conditions, possibly related to orbital forcing. The boundary between this lower unit and an overlying upper unit is an unconformity of regional extent marked by a change in the depositional architecture and an abrupt shift in palaeocurrent pattern. The Upper Unit (200 m thick) is characterized by stacked sets of simple cross strata, each ~3 to 10 m thick, which are indicative of the migration and accumulation of large aeolian dunes that lacked interdune flats of appreciable size, and which accumulated as a dry aeolian system. Palaeocurrent data indicates aeolian sand transport dominantly to the present-day south. This succession is interpreted to have accumulated during a long-lived episode of hyper-aridity. Locally, the upper unit includes minor fluvial deposits that may record a short-lived event of heightened humidity, or a rare flood event by fluvial systems sourced from the basin margin. The combination of the palaeowinds data with 1.6 - 1.5 Ga palaeogeographic maps demonstrate a good correlation between atmospheric circulation and land mass distribution. At 1.6 to 1.54 Ga São Francisco Craton has been located between mid-latitudes and equatorial zone. The wind regime records from the cross-strata of the Lower Unit are consistent with the palaeogeographic positions of São Francisco between 25º to 35º S, prevail a zonal wind pattern. At 1.54 to 1.5 Ga the large land mass (São-Francisco-Congo and Siberian cratons) drifted farther north reaching palaeolatitudes between 30º S and 30ºN. At that time the São Francisco Craton has been located in the equatorial zone. This palaeogeography is consistent with the northwestern palaeowinds directions recorded in the Upper Unit which dominates a monsoonal wind pattern.

Este trabalho compreende uma abordagem teórico-metodológica para o estudo dos processos de formação (culturais e naturais) da camada preta que recobre o sítio Jabuticabeira II (Santa Catarina). A partir da adaptação da análise de fácies sedimentares foi desenvolvido um método para a descrição, classificação, caracterização e interpretação de sedimentos arqueológicos em sítios estratificados. Tal método foi desenhado para envolver numa mesma abordagem analítica os processos culturais e naturais como agentes ativos na configuração de corpos arqueossedimentares. Na camada preta do sítio Jabuticabeira II, a análise de arqueofácies proposta permitiu aproximar aos comportamentos deposicionais e processos naturais responsáveis pela conformação deste complexo fenômeno de deposição cultural. / This work represents a theoretical and methodological approach for the study of formation processes (both cultural and natural) of the black layer that covers the Jabuticabeira II site (Santa Catarina). From adaptation of sedimentary facies analyses a method for classification, characterization and interpretation of archaeological sediments in stratified sites was developed. Such method aims to embrace in the same analytical approach both cultural and natural processes as active agents in the configuration of archaeosedimentary bodies. In the black layer of Jabuticabeira II, the proposed archaeofacies analyses allowed the approximation of depositional behaviours and natural processes responsible for the conformation of this complex phenomenon of cultural deposition.