Claiton M. S. Scherer

Integrated stratigra phic and geochemical study of the Santa Maria and Caturrita formations (Triassic of the Paraná Basin), southern Brazil

Abstract Several analytical techniques were applied in the study of the Alemoa Member (Santa Maria formation) and Caturrita formation to make an assessment of changing paleoenvironmental conditions through the Triassic succession of southern Brazil. This included a integration of petrography, X-ray diffractometry, scanning electron microscopy and chemical analysis of both major and minor elements, as well as uranium (U) and thorium (Th). The studied succession comprises part of the Triassic continental deposits of the Parana Basin in South America and represents channel deposits surrounded by fine-grained flood plain facies. This stratigraphic interval is interpreted as an anastomosing fluvial system (Alemoa Member) that has gradually evolved into a braided system (Caturrita formation). The chemical index of alteration (CIA), which is determined through the rock chemical composition, was used to highlight weathering processes on primary minerals. The CIA follows an upward trend representing an increase on weathering conditions from the Alemoa Member to the Caturrita formation. The deep chemical alteration in the Caturrita formation suggests weathering under a humid, possibly tropical climate. These results are in agreement with U and Th analysis. The Th/U ratios rise toward the top of the section (Caturrita formation) suggesting an increasingly more humid climate. Thus, the gradual upward shift from an anastomosing to a braided fluvial style is ascribed to a climate change, and related increase in palaeorainfall. The existence of interstratified illite–smectite clay minerals, mud cracks and caliche concretions within the flood plain deposits suggests deposition under a hot climate with alternating wet and dry seasons. Therefore, the results of this work show that the integration of facies studies with mineralogical and geochemical analysis enhances our ability to perform detailed paleoenvironmental studies on continental successions.

New Regional Correlations Between the Congo, Paraná and Cape-Karoo Basins of Southwest Gondwana

Pioneering stratigraphic correlations by J. Keidel and A. du Toit, in the first half of the twentieth century, first highlighted significant similarities between the age-rock sequences in southern Africa and eastern South America, supporting A. Wegener’s concept of a united Gondwana supercontinent. Based on subsequent field investigations and modern sedimentary basin analysis of the Congo Basin of central Africa and the Parana Basin of southeastern Brazil, we revisit these early correlations and derive new paleogeographic reconstructions of the interior of southwest Gondwana. Following late Neoproterozoic-Early Cambrian amalgamation of Gondwana, earliest Paleozoic continental red-bed sediments were deposited regionally southward across the peneplained Central African and Kalahari Shields. Thereafter, Ordovician-Devonian subsidence along a vast shallow marine platform bordering the southwestern margin of Gondwana linked the Parana Basin with the Cape-Karoo Basin of South Africa. Equivalent sequences are absent in the Congo Basin. In contrast, succeeding Carboniferous-Permian and Triassic successions are similar in all the Congo, Parana and Cape-Karoo Basins, including thick transgressive glacial and deglaciation sequences overlain by progressively terrestrial and arid sediments, which suggest a single Central West Gondwana Basin (CWGB) complex. This late Paleozoic-early Mesozoic cycle of subsidence of the CWGB can possibly be linked to long wavelength flexure of Gondwana continental lithosphere related to the Mauritanian-Variscan and Cape-de la Ventana orogens along the northwestern and southern margins of the supercontinent, around ca. 300 Ma and 250 Ma, respectively. Following Jurassic-Cretaceous hot and arid sedimentation across southwest Gondwana culminated in widespread deposition of northerly-derived aeolian dunes, episodically interrupted by successive eruption of Large Igneous Provinces during the initial phases of Gondwana break-up (ca. 183 Ma and 132 Ma). This shared sedimentation and climatic history of the Congo, Parana and Cape-Karoo Basins was then disrupted by the Early Cretaceous opening of the South Atlantic Ocean and the Kalahari epeirogeny, after which the Congo Basin survived and recorded intermittent phases of lacustrine and fluvial deposition.

Ontological primitives for visual knowledge

In the last few years, we have analyzed the best alternatives for acquiring and processing visual knowledge with the goal of supporting problem solving. We call visual knowledge the set of mental models that support the process of reasoning over information that comes from the spatial arrangement and visual aspects of entities. Also, visual knowledge is implicit, meaning that it is difficult to be explicitly represented solely with propositional constructs. In this paper, we describe a representational approach that helps geologists in capturing and applying this kind of knowledge, in order to support software development applied to interpretation tasks in Petroleum Geology applications. Our approach combines propositional constructs with visual pictorial constructs in order to model visual knowledge of geologists. These constructs are proposed in a strong formal model, founded by Formal Ontology concepts. Based on these constructs, we develop a full ontology for stratigraphic description of sedimentary facies. The Formal Ontology background and the approach are detailed and evaluated through the paper.

Visual Interpretation of Events in Petroleum Geology

In visual domains, the tasks are accomplished through intensive use of visual knowledge. In this paper, we are interested in the visual interpretation task, which is prevalent in many visual domains. We investigate the role played by foundational ontologies in reasoning processes that deals with visual information, as those that are performed in visual interpretation tasks. We propose an approach for visual interpretation that combines ontologically well founded domain ontologies, a reasoning model, and a cognitively well founded meta-model for representation of inferential knowledge. Our approach was effectively applied in the task of visual interpretation of depositional processes, within the Sedimentary Stratigraphy domain.

Ontology for Imagistic Domains: Combining Textual and Pictorial Primitives

This paper proposes a knowledge model for representing concepts that requires pictorial as well as conceptual representation to fully capture the ontological meaning. The model was built from the proposition of pictorial primitives to be associated to the original conceptual primitives. The formalized pictorial content is then used to provide an organization to the domain, based on the visual characteristics of the objects as humans are used to do. The combination of both primitives allows the definition of domain ontologies to support visual interpretation activities. The approach was applied to build the Stratigraphy ontology for the definition of Sedimentary Facies and Structures.

Visual interpretation of events in petroleum exploration

We propose an ontology-based approach for visual interpretation tasks.Our approach applies ontological meta-properties of a foundational ontology.We propose a cognition-inspired representation structure for inferential knowledge.We apply our approach for interpreting depositional processes, in Petroleum Geology. In visual domains, such as Medicine, Meteorology and Geology, the tasks are accomplished through intensive use of visual knowledge. In this work, we focus in an essential kind of task that is performed in many visual domains: the visual interpretation task. We call visual interpretation the expert reasoning process that starts with the perception of visual features of domain objects and results in the understanding of the scene. We propose a top-down approach for solving visual interpretation tasks, which is based on symbolic pattern matching supported by well-founded ontologies. Our approach combines well-founded domain ontologies; a meta-model for representing inferential knowledge, which is based on the notion of perceptual chunks; and a reasoning model for visual interpretation. The proposed model was applied for developing an expert system for automating the task of visual interpretation of depositional processes, which a crucial task for petroleum exploration.

Semantic image interpretation of gamma ray profiles in petroleum exploration

This paper presents the S-Chart framework, an approach for semantic image interpretation of line charts; and the InteliStrata system, an application for semantic interpretation of gamma ray profiles. The S-Chart framework is structured as a set of knowledge models and algorithms that can be instantiated to accomplish chart interpretation in all sorts of domains. The knowledge models are represented in three semantic levels and apply the concept of symbol grounding in order to map the representation primitives between the levels. The interpretation algorithms carry out the interaction between the high-level symbolic reasoning, and the low-level signal processing. In order to demonstrate the applicability of the S-Chart framework, we developed the InteliStrata system, an application in Geology for the semantic interpretation of gamma ray profiles. Using the developed application, we have interpreted the charts of two gamma ray profiles captured in petroleum exploration wells, indicating the position of stratigraphic sequences and maximum flooding surfaces. The results were compared with the interpretation produced by an experienced geologist using the same data input. The system carried out interpretation that were compatible with the geologist interpretation over the data. Our framework has the advantage of allowing the integration of existing domain ontologies with domain independent visual knowledge models and also the ability of grounding domain concepts in low-level data.

A Symbol Grounding Model for Semantic Interpretation of 2-D Line Charts

Representing symbol grounding is a recurrent subject of discussion in knowledge-based vision systems. The \emph{symbol grounding problem} refers to the issue of connecting symbols of a symbol system to their low-level projections within perceptual input. In this paper, we present our ongoing efforts in formalizing an ontologically-founded, domain-independent visual knowledge model that allows one to represent the grounding relation between high-level domain entities and basic image features of 2-D line charts. The characterization of the grounding relations according its ontological status should provide a better criteria in deciding which domain entities can be grounded, improving reusability of our model in multiple interpretation domains and better structuring of the grounding relations. Additionally, we present an algorithm for visual interpretation using the proposed model. The framework of models and algorithm has been implemented in a visual interpretation system for Geology domain. One test case is shown as running example.

Análise sismoestratigráfica da seção rifte da Bacia de Santos, Brasil

The Santos Basin, despite its surmount significance due to the pre-salt reservoirs, has limited geological information well-logs, 3D seismic or good quality 2D seismic for the rift section. The present work aims at integrating seismic stratigraphic analysis and proposing a tectonic-stratigraphic evolution model for the rift section of the basin. Seismic stratigraphic analysis involved interpretation of reflectors, which is the base of seismic stratigraphic units identification and seismic facies characterization. The result was the definition of 16 seismic stratigraphic units, four seismic facies (including the sag ), and the development of chronostratigraphic charts of events adapted to the seismic context. Based on the adaptation of the stacking patterns to tectonic activity changes model, it was possible to delimit the rift initiation system tract, the high tectonic activity system tract, the low tectonic activity system tract and the post-rift, represented by the sag . The development of each tectonic system tract responded to variations in controlling factors of the lacustrine basin, interpreted as the relative balance between the rate changes in the accommodation space generated by tectonic and sediment supply influenced by climate.

Reconhecimento e análise das fácies sísmicas nas sucessões rift das bacias de Campos e Santos

Apresentando reservatorios em aguas profundas, o pre-sal das bacias de Campos e Santos e um cenario com depositos heterogeneos e complexos, e assim traz novos desafios para a interpretacao sismica. O presente trabalho tem como objetivo a caracterizacao sismica do intervalo rifte (de idade Hauteriviano Superior ao Barremiano, imediatamente abaixo dos reservatorios pre- -sal) nas bacias de Campos e Santos com a utilizacao de dados de sismica 2D e dois perfis de pocos. Foram analisadas as texturas sismicas e com a integracao dos dados litologicos se definiu tres sismofacies correspondentes: Sismofacies 1 (deposito de falha de borda) – apresenta comportamento semelhante em ambas as bacias e com ocorrencia encaixada na falha de borda em uma zona ampla e bem definida; Sismofacies 2 (deposito de sedimentos finos) – amplamente identificada nas bacias de Campos e Santos e que grada lateralmente para a sismofacies 3; Sismofacies 3 (deposito de grainstones e rudstones ) – em ambas as bacias tem ocorrencia restrita e de ocorrencia erratica, tanto em zonas altas da margem flexural, quanto nas zonas profundas proximas do depocentro dos meio-grabens analisados.