Stratigraphy and volcanic facies architecture of the Torres Syncline, Southern Brazil, and its role in understanding the Paran¨¢-Etendeka Continental Flood Basalt Province

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• 作者：Breno L. Waichel^a ; ^{breno@cfh.ufsc.br} ; Evandro F. de Lima^b ; Adriano R. Viana^c ; Claiton M. Scherer^b ; Gilmar V. Bueno^c ; Gabriel Dutra^b
• 关键词：Volcanic rocks ; Stratigraphy ; Facies architecture ; Torres Syncline ; Paraná ; &ndash ; Etendeka CFB
• 刊名：Journal of Volcanology and Geothermal Research
• 出版年：2012
• 出版时间：15 February, 2012
• 年：2012
• 卷：215-216
• 期：Complete
• 页码：74-82
• 全文大小：2701 K

文摘

The Torres Syncline is a large structure that constitutes the eastmost outcrop of the Paran¨¢-Etendeka CFB in South American side, and this work focuses the stratigraphy and facies architecture of the volcanic pile in the syncline. The volcanic sequence along the study area permits the division of three regions: main valley, intermediate zone and south hinge, each of them with distinct stratigraphy, which probably reflects the structural evolution of the syncline. The stratigraphy of the Torres Syncline is composed by: 1 ?Botucatu palaeoerg; 2 ?Basic volcanic episode I; 3 ?Basic volcanic episode II, 4 ?Acidic volcanic I, 5 ?Basic volcanic episode III and 6 ?Acidic volcanic episode II. The five volcanic episodes recognized in study area can be related to five volcanic facies architecture: compound-braided, tabular-classic, tabular/lobate escoriaceous, dome-field (acidic lavas) and tabular flows (acidic lavas). The basic episode I is composed by pahoehoe flows with a compound-braided facies architecture that covered the Botucatu palaeoerg. The basic episode II is a tabular-classic facies architecture predominantly composed by simple flows (10-20 m thick) reaching the total thickness of ~ 500 m in main valley. The acidic episode I is exposed in main valley and south hinge, and is composed by acidic lavas forming lava dome-field facies architecture with a thickness of ~ 150 m. The basic episode III is predominantly constituted by ?em>a?em>¨¡ flows with tabular/lobate escoriaceous facies architecture. The acidic episode II is constituted by tabular flow volcanic facies (acidic flows) and outcrops all along the study area. The Torres Syncline constitute the eastmost on-shore exposures of the Paran¨¢-Etendeka CFB in South American side and detailed stratigraphic, volcanological and structural studies in these area, coupled with correlation with Huab Basin (NW Nam¨ªbia, Africa) will aim the understanding of the Gondwana breakup process and the early stages of the South Atlantic margin opening.