Alluvial-eolian interaction in a Cambrian rift margin: the Pedra das Torrinhas and Pedra Pintada formations (Guaritas Group, RS)

Autor(es)

André Marconato ^[1] ; Renato P. Almeida ^[2] ; Maurício G. M. Santos ^[3] ; Jorge E.S. Nóbrega ^[4] ; Rogério B. Souza ^[5]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação em Geoquímica e Geotectônica - Brasil

^[2] Universidade de São Paulo. Instituto de Geociências. Departamento de Geologia Sedimentar e Ambiental - Brasil

^[3] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação em Geoquímica e Geotectônica - Brasil

^[4] Universidade de São Paulo. Instituto de Geociências. Programa de Pós-Graduação em Geoquímica e Geotectônica - Brasil

^[5] Petróleo Brasileiro S.A.. Universidade Petrobras - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Anais da Academia Brasileira de Ciências; v. 81, n. 4, p. 819-836, 2009-12-00.

Resumo

This work presents a study of selected outcrops from the Pedra das Torrinhas Formation of the Guaritas Group (Cambrian, Camaquã Basin), near the basin bordering Encantadas Fault Zone. The studied succession includes alluvial fan deposits that pass laterally into eolian deposits. Sedimentary facies and architectural element analysis were performed, followed by sedimentary petrography and microscopic porosity analysis, aiming to characterize the porosity of the deposits and its spatial distribution. The main objective was to contribute to a better understanding of the porosity spatial distribution in depositional systems characterized by the interaction between alluvial and eolian processes, with special reference to deposits formed prior to the development of terrestrial plants. Porosity values are related to depositional processes, with higher porosities associated to eolian dune deposits (mean of 8.4%), and lower porosity related to interdunes (mean of 3.4%) and alluvial fans (mean of 4.3%). Architectural elements analysis revealed the spatial relationships of these deposits, a response to the interplay of the eolian and alluvial processes. The integration of porosity data reveals that the interaction of alluvial and eolian processes results in heterogeneous distribution of porosity at the facies association scale. Eolian reworking of alluvial facies increases porosity whereas sheet-flood and other alluvial processes in the interdune areas reduce porosity. (AU)

• Processo FAPESP: 06/59724-4 - Interacoes entre paleossistemas deposicionais aluviais e eolicos na formacao pedra das torrinhas (grupo guaritas, cambriano-rs): arquitetura deposicional e modelamento analogo de reservatorios...
• Beneficiário: André Marconato
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica
• Processo FAPESP: 06/50655-0 - Controles tectonicos no preenchimento de rifts interiores: o caso do grupo guaritas (cambriano, rs).
• Beneficiário: Renato Paes de Almeida
• Modalidade de apoio: Auxílio à Pesquisa - Regular