Evolution of a rift basin dominated by subaerial deposits: The Guaritas Rift, Early Cambrian, Southern Brazil

Autor(es)

de Almeida, Renato P. ^[1] ; Janikian, Liliane ^[2] ; Fragoso-Cesar, Antonio Romalino S. ^[1] ; Marconato, Andre ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: SEDIMENTARY GEOLOGY; v. 217, n. 1-4, p. 30-51, MAY 15 2009.
• Citações Web of Science: 19

Resumo

Most existing models for the evolution of rift basins predict the development of deep-water depositional systems during the stage of greatest tectonic subsidence, when accommodation generation potentially outpaces sedimentation. Despite this, some rift basins do not present deep-water systems, instead being dominated by subaerial deposits. This paper focuses on one of these particular rift basins, the Cambrian Guaritas Rift, Southern Brazil, characterized by more than 1500 m of alluvial and aeolian strata deposited in a 50-km-wide basin. The deposits of the Guaritas Rift can be ascribed to four depositional systems: basin-border alluvial fans, bedload-dominated ephemeral rivers, mixed-load ephemeral rivers and aeolian dune fields. These four systems are in part coeval and in part succeed each other, forming three stages of basin evolution: (i) Rift Initiation to Early Rift Climax stage, (ii) Mid to Late Rift Climax stage, and (iii) Early Post-Rift stage. The first stage comprises most of the Guaritas Group and is characterized by homogeneous bed-load-dominated river deposits, which do not clearly record the evolution of subsidence rates. The onset of sedimentation of finer-grained deposits occurred as a consequence of a reactivation event that changed the outline of the basin and the distribution of the nearby highlands. This strongly suggests that the capture of the main river system to another depression decreased the sediment supply to the basin. The study of the Guaritas Rift indicates that rift basins in which the sediment supply exceeds the accommodation generation occur as a consequence of moderate subsidence combined with the capture of a major river system to the basin during the initial stages of basin evolution. In these basins, changes in the average discharge of the river system or tectonic modification of the drainage network may be the major control on the stratigraphic architecture. (c) 2009 Published by Elsevier B.V. (AU)

• 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
• Processo FAPESP: 00/07510-4 - Estratigrafia de seqüências em rifts do fim do Neoproterozóico e início do Paleozóico no Rio Grande do Sul
• Beneficiário: Antonio Romalino Santos Fragoso-Cesar
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 05/57939-0 - Relações entre atividade plutônica e formação de bacias sedimentares: uma abordagem integradora para evolução tectônica das unidades ediacaranas do Rio Grande do Sul
• Beneficiário: Antonio Romalino Santos Fragoso-Cesar
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 05/53522-8 - Correlações estratigráficas entre as sucessões vulcano-sedimentares ediacaranas da Região Sul do Brasil e suas relações com as grandes glaciações neoproterozóicas
• Beneficiário: Liliane Janikian Paes de Almeida
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado