Phanerozoic magmatism in the Parnaíba Basin: characterization of igneous bodies (well logs and 2D seismic sections), geometry, distribution and sill emplacement patterns
I. Trosdtorf, Jr, J. M. Morais Neto, S. F. Santos, C. V. Portela Filho, T. A. Dall Oglio, A. C. M. Galves, A. M. Silva, 2018. "Phanerozoic magmatism in the Parnaíba Basin: characterization of igneous bodies (well logs and 2D seismic sections), geometry, distribution and sill emplacement patterns", Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil, M. C. Daly, R. A. Fuck, J. Julià, D.I.M. MacDonald, A. B. Watts
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The Parnaíba Basin, like other Brazilian Paleozoic intracratonic basins, contains intrusive igneous bodies in its sedimentary section in the form of dykes and, mainly, thick sills. The identification of the geometry and the emplacement mechanism are important for the determination of the traps controlling gas and/or oil accumulations. A variety of models available in the literature suggests a complex relationship between the magma and the host rock. Several factors, such as the density and pressure of the magma injection, steam generation, regional and local stress fields, and the rheology of the host rock, work together controlling emplacement, expansion and the final geometry of intrusions in the sedimentary column. Well logs show a conspicuous signature (e.g. gamma-ray curve with paunchy feature) for the igneous bodies (sills). Many sills occur parallel to the bedding, generally intruding thick sections of shales along the contact of the lithostratigraphic units of the Longá-Poti, Pimenteiras-Cabeças and Tianguá-Jaicós formations. Seismic sections reveal a variety of geometries, including layer parallel, saucer-shaped, planar transgressive and fault block. By far the most common sill geometry is the layer parallel, which is able to reach up to hundreds of kilometres in extent, and has minimal thickness ranging between 2 and 5 m, and with a maximum of around 250 m.
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Cratonic Basin Formation: A Case Study of the Parnaíba Basin of Brazil
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Cratonic basins are large, distinctive features of the continental crust. They are preferentially developed on thick continental lithosphere, are typically sub-circular in shape and subside over periods of hundreds of millions of years. They are also endowed with significant resources. However, in spite of their location in continental interiors and often well-known geology, the subsidence driving mechanism and tectonic setting of these basins remains controversial.
This volume presents both lithospheric and basin scale datasets acquired specifically to interrogate the tectonic process of cratonic basin formation. Focused on the Silurian to Triassic Parnaíba cratonic basin of Brazil, the papers discuss the results of a multidisciplinary basin analysis project comprising new geophysical, geological and geochemical data. This unique dataset enables the characterization of the lithospheric crust and mantle beneath the Parnaíba Basin, constrains the detailed evolution of the basin itself, and enables comparisons with cratonic basins globally. Several convergent themes emerge providing new and powerful constraints for models of the driving mechanisms of these enigmatic basins.