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O método Caracterização Multiescalar de Reservatórios (Camures) vem se consolidando como uma importante ferramenta e que tem auxiliado na caracterização dos mais diferentes tipos de afloramentos e seções de rochas sedimentares. O objetivo deste trabalho compreende a aplicação desse método em um afloramento da Formação Lagoa do Jacaré, Grupo Bambuí, representado por uma pedreira desativada na região de Paraopeba, centro-norte de Minas Gerais. Para tanto, utilizaram-se diferentes ferramentas investigativas em macro, meso e microescalas de análise para caracterização dessa unidade nesse afloramento. A caracterização litofaciológica de detalhe na pedreira revelou cinco litofácies carbonáticas principais. Dados geofísicos de Ground Penetrating Radar (GPR) e raios gama foram levantados para auxiliar no reconhecimento das principais geometrias e litologias presentes na área, bem como na correlação lateral dos perfis levantados na pedreira. A análise petrográfica microscópica mostra a ocorrência de seis fácies. A análise das litofácies e estruturas sedimentares presentes apontam para deposição sob influência de ondas de tempestade em diversos ciclos tempestíticos em plataforma carbonática rasa. Essa sequência é definida na base por brechas intraclásticas, representando momentos de alta energia, passando a momentos de menor energia que favorecem a deposição carbonática fina com estratificações hummocky e plano-paralelas, marcas onduladas associadas, até raros momentos de calmaria com deposição de sedimentos carbonáticos finos na transição antepraia-plataforma (shoreface-offshore).

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A Bacia São José do Itaboraí é uma depressão elíptica fechada encravada em rochas do embasamento cristalino, sendo sua origem associada ao desenvolvimento do Sistema de Rifte continental do sudeste do Brasil. A bacia foi preenchida principalmente por sedimentos carbonáticos e calcário travertino é a fácies predominante. Estudos mineralógicos através de microscopia de luz transmitida, difração de raios X e MEV/EDS e determinações de porosidade e permeabilidade foram efetuadas no travertino e nas fácies subordinadas brecha carbonática e grainstone oolítico, com o propósito de avaliar o sistema de porosidade de rochas carbonáticas. As investigações nessas três litofácies apontaram densidades entre 2,66 e 2,70 g/cm3 e taxas baixas a muito baixas de porosidade e permeabilidade, menor que 2,5% e 0,2 milidarcys, respectivamente. As principais causas para valores tão baixos residem na forte cimentação das rochas aliada à recristalização de cristais de calcita, à alteração de silicatos e ao preenchimento de poros por minerais diagenéticos. Este trabalho mostra que o fluxo de fluidos em rochas reservatório pode ser mais bem compreendido ao serem usados métodos de determinação mineralógica combinados com petrofísica.

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Carbonate rocks from the Macaé Group (Albian) represent an example of carbonate sedimentation related to the drift phase in Campos Basin. This study presents depositional features, integrating them with diagenetic and stratigraphic aspects of the Macaé Group carbonates including the upper part of the Quissamã Formation and the lower part of the Outeiro Formation. Macroscopic analyses in cores and microscopic ones in thin sections allowed the recognition of eleven sedimentary facies - nine of them corresponding to the Quissamã Formation and two of them representing the Outeiro Formation. These facies were grouped into five facies associations. Oolitic grainstones and oncolitic grainstones are interpreted to be deposited in shallow depth probably in shoals above the fair weather wave base. The interbanks between shoals were formed in less agitated waters and characterized by deposition of peloidal bioclastic packstones and wackestones representative of sedimentation in calm waters. Bioclastic packstones and oolitic packstones/wackestones represent allochthonous deposits related to the beginning of the regional drowning that occur in upper Quissamã Formation. Pithonellids wackestones and bioclastic wackestones with glauconite are related to deep water deposits, characteristics of the Outeiro Formation. Post-depositional features revealed the action of diagenetic processes as, micritization, cimentation, dissolution, compaction, dolomitization and recrystallization occurred during the eoand mesodiagenesis phases. Vertical facies analysis suggests shallowing upward cycles stacked in a sequence progressively deeper towards the top (from the Quissamã Formation to the Outeiro Formation). [ABSTRACT FROM AUTHOR]

Abstract: As part of a study of the Cenomanian–Coniacian sedimentary succession in the Sergipe Basin in northeastern Brazil, microfacies analyses were tested for possible chronostratigraphic application. The common and widespread remains of roveacrinid echinoderms proved useful for intrabasinal biochronostratigraphy. Local dolomitization in the basin, which destroyed most other fossil remains, left the magnesian-calcitic roveacrinid skeletons largely unaffected. Thus, where diagnostic fossils are scarce or lacking, roveacrinids may provide an ancillary means of chronostratigraphic correlation. The forms recorded from Sergipe are described, and a stratigraphic range chart is presented for intrabasinal application, with the possibility of regional or even global correlation either qualitatively (presence/absence patterns) or quantitatively (eco-event patterns). Several roveacrinid abundance horizons have been reported worldwide in relation to sea level changes and associated hypoxic events, during which roveacrinids developed abundant opportunistic populations. The present study of the Sergipe Basin provides a basis for comparisons and correlations of roveacrinid occurrences in the mid-Cretaceous succession of the South Atlantic continental margin basins and ODP/DSDP drill cores. [Copyright &y& Elsevier]

Carbonate rocks from the Macaé Group (Albian) represent an example of carbonate sedimentation related to the drift phase in Campos Basin. This study presents depositional features, integrating them with diagenetic and stratigraphic aspects of the Macaé Group carbonates including the upper part of the Quissamã Formation and the lower part of the Outeiro Formation. Macroscopic analyses in cores and microscopic ones in thin sections allowed the recognition of eleven sedimentary facies - nine of them corresponding to the Quissamã Formation and two of them representing the Outeiro Formation. These facies were grouped into five facies associations. Oolitic grainstones and oncolitic grainstones are interpreted to be deposited in shallow depth probably in shoals above the fair weather wave base. The interbanks between shoals were formed in less agitated waters and characterized by deposition of peloidal bioclastic packstones and wackestones representative of sedimentation in calm waters. Bioclastic packstones and oolitic packstones/wackestones represent allochthonous deposits related to the beginning of the regional drowning that occur in upper Quissamã Formation. Pithonellids wackestones and bioclastic wackestones with glauconite are related to deep water deposits, characteristics of the Outeiro Formation. Post-depositional features revealed the action of diagenetic processes as, micritization, cimentation, dissolution, compaction, dolomitization and recrystallization occurred during the eo- and mesodiagenesis phases. Vertical facies analysis suggests shallowing upward cycles stacked in a sequence progressively deeper towards the top (from the Quissamã Formation to the Outeiro Formation).