3D MODEL OF THE TORRES SYNCLINE IN THE PARANÁ-ETENDEKA PROVINCE, SOUTH ATLANTIC MARGIN

Abstract:

The Paraná-Etendeka Volcanic Province (PEVP) is Early Cretaceous in age and precedes the fragmentation of the south Gondwana. These volcanic rocks cover an area in excess of 1,200,000 km² and can reach a maximum thickness of 1,700 m. The PEVP is composed mainly of tholeiitic basalts and subordinately by andesites and rhyolites/quartz-latites. Recently new models considering physical characteristics of the lava flow stratigraphy on both sides, Africa and South America, have been built providing a new vision of the volcanic stratigraphy and flow morphologies inside the province. This work presents a 3D model of the volcanic sequence at theTorres Syncline (Brazil). The 3D model was build using the PETREL E&P Software Platform. Geological sections based on field data and Log data from Paraná Basin (Gama-ray and soniclogs) were used to build the model. The Torres Syncline is a tectonic structure located in southern Brazil with the main orientation NW-SE. In Torres Syncline the basal portion is characterized by pahoehoe lava flows in a compound braided architecture, followed by rubbly lavas in a tabular classic architecture, and in the upper portions silicic units interbedded with basaltic lavas. The central portion of the volcanic pile is characterized by thick tabular lavas with rubbly tops (25-50 m thick). These flows have an internal structure divided in four parts: a smooth vesicular base, aphanitic massive cores with irregular joints, upper vesicular portion and a rubbly top. This unit is thicker along of the Torres Syncline and represents the main phase of the volcanism. Silicic units occur in the upper parts of the PEVP stratigraphy and include lava domes interbedded with rubbly flows and thick tabular flows. The Torres Syncline and Huab constituted one Basin features single active structure in the Early Cretaceous and during the main rifting phase. The onset of the volcanism was characterized by low effusion rate eruptions over the paleoerg, forming pahoehoe flow fields. The main phase of volcanism is build up by thick tabular rubbly pahoehoe flows, formed by larger volume sequences (slightly high effusion rates), that cover the initial pahoehoe flows. At the upper portion of the sequence, the volcanism is more differentiated forming silicic lavas.