Associação de litofácies, interação lava-sedimento e caracterização sísmica do magmatismo Serra Geral na região de Uberlândia e Araguari (MG)

Esta tese apresenta os estudos realizados na porção norte da Província Ígnea Paraná-Etendeka (PIPE), com enfoque na estratigrafia, nas interações lava-sedimento e na caracterização em imagem sísmica de diferentes cenários de transição basalto-sedimento envolvendo sucessões vulcânicas. Os resultados são apresentados sob a forma de três artigos científicos submetidos a revistas internacionais. No primeiro artigo são definidas quatro associações de litofácies: pillow lavas, derrames pahoehoe compostos e simples, peperito e brecha vulcânica com matriz infiltrada. Derrames pahoehoe simples, compostos e pillow lavas caracterizam o início do magmatismo, enquanto peperito e derrames espessos ocorrem nas porções superiores da estratigrafia da área. Essas lavas correspondem a magmas de alto-TiO2 do tipo Pitanga. Na área de estudo, a ocorrência de feições formadas em condições úmidas reflete condições ambientais diferentes daquelas previamente descritas como áridas em outras porções da PIPE. No segundo artigo são apresentados e discutidos alguns dos produtos de interação entre lava e sedimento estudados nesta tese como, por exemplo, peperito, estrutura de carga, lavas invasivas, peperito do tipo pillow e pseudocrateras (rootless cones). Em geral, esses produtos afetam poucos metros além do contato lava-sedimento. Entretanto, lavas invasivas podem estender esses impactos para uma área maior. O terceiro artigo combina modelo digital de afloramento obtido na Província Ígnea do Atlântico Norte e dados petrofísicos da área estudada na PIPE, para a construção de modelos sísmicos sintéticos envolvendo quatro cenários geológicos diferentes. Essas imagens sísmicas foram geradas utilizando fontes com diferentes conteúdos de frequência com o objetivo de avaliar as variações da detectabilidade e características das reflexões sísmicas ao longo da transição basalto-sedimento. Foi possível observar como a variabilidade geológica associada à transição basalto-sedimento pode influenciar o imageamento sísmico e complicar a interpretação. Em particular, feições como lavas invasivas podem ser difíceis de diferenciar de soleiras em dados sísmicos e, portanto, os potenciais impactos nas propriedades e conectividade do reservatório devem ser avaliados cuidadosamente.This thesis presents the study made in the northern portion of the Paraná-Etendeka Igneous Province, focusing on the stratigraphy, lava-sediment interaction and seismic characterization of different basalt-sediment transition scenarios involving volcanic successions. The results are presented in three scientific manuscripts submitted to international journals. In the first manuscript four lithofacies association were defined: pillow lavas, compound and simple pahoehoe, peperite and sedimentary-infill basalt breccia. The onset of the volcanic activity is characterized by pillow lavas, simple and compound pahoehoe, whereas peperite and thick lava flows occur it the upper stratigraphic levels of the study area. These studied lavas are compatible with high-TiO2 Pitanga magma type. In the study area, the presence of features formed in wet conditions reflect different environmental conditions from those previously described as arid in other portions of the PEIP. The second manuscript present and discuss some products of lava-sediment interactions such as peperite, loading, invasive flows, pillow-like peperite and rootless cones. These interactions are generally restricted to a few meters from the lava-sediment contact. However, lava invasion may extend this impact further. The third manuscript combines 3D virtual outcrop model from the North Atlantic Igneous Province with laboratory petrophysical measurements from Paraná-Etendeka Igneous Province field outcrop analogues to develop synthetic seismic forward models for four different base-basalt transition scenarios. The models were run using source wavelets with different frequency spectrums in order to assess variations in seismic reflection character and detectability of the volcanic features along with the basalt-sediment transition. The results demonstrate how geological variability associated with the basalt-sediment transition can influence seismic imaging and complicate interpretation. In particular, features such as invasive lava flows may be challenging to differentiate from sill intrusions in seismic data, and therefore their potentially very different impacts on reservoir properties and connectivity must be appraised carefully

Organic walled microfossils in wet peperites from the early Cretaceous Paraná-Etendeka volcanism of Brazil

Abstract Large igneous provinces (LIPs) are major magmatic events that have a significant impact on the global environment and the biosphere, for example as triggers of mass extinctions. LIPs provide an excellent sedimentological and geochemical record of short but intense periods of geological activity in the past, but their contribution towards understanding ancient life is much more restricted due to the destructive nature of their igneous origin. Here, we provide the first paleontological evidence for organic walled microfossils extracted from wet peperites from the Early Cretaceous Paraná-Etendeka intertrappean deposits of the Paraná basin in Brazil. Wet peperites are a volcaniclastic rock formed by the interaction of lava and subaqueous sediments.The Paraná-Etendeka was formed during the Valanginian (ca. 132 Ma) as a continental flood basalt in present day South America and Namibia, and released enormous amounts of carbon dioxide, sulfur dioxide, methane and hydrogen fluoride into the atmosphere. The organic walled microfossils recovered from the Paraná-Etendeka peperites include pollen grains, spores, acritarchs, and other remains of unidentifiable organic matter. In addition to the peperites, organic walled microfossils were also found in heterolithic sandstones and interpillow sandstones. Our findings represent the first insight into the biodiversity of the Paraná Basin during the Early Cretaceous during a period of intense magmatism, and the microfossil assemblages corroborate a regional paleoclimatic transition from arid to more humid conditions that were likely induced by the volcanic activity. We corroborate the potential of wet peperite rocks as a valuable source of paleobiological data and emphasize the importance of sampling volcaniclastic units that have been traditionally considered with lower fossiliferous potential due to their igneous origin