Evolution of the Upper Jurassic and Lower Cretaceous vulcano-sedimentary record – Southeast portion of the Paraná Basin, Brazil

Abstract

The period between the Late Jurassic and Early Cretaceous on the southernmost part of the Paraná Basin was characterized by the accumulation of the aeolian system from the Botucatu Formation, which was entirely preserved by the volcanic flows of the Serra Geral Formation. To a lesser extent, intense basic and acid magmas covered an extensive aeolian continental environment. However, in the central region of the state of Rio Grande do Sul, in the southernmost part of the Paraná Basin, data from 29 outcrops, 13 vertical stratigraphic profiles, and 334 paleocurrent measurements exposed fluvial–aeolian deposits of the Guará Formation in contact with volcanic rocks of the Serra Geral Formation. This study considers new temporal and spatial relationships between the fluvial–aeolian, aeolian, and volcanic systems developed in this temporal range. For this purpose, facies analysis and architectural elements were used to reconstruct the evolution of this volcano-sedimentary record. Nineteen facies grouped into five facies associations (braided fluvial channel, ephemeral braided fluvial channel, aeolian sand sheets, aeolian dunes, and volcanic plain) were identified according to their architectural elements in the Guará, Botucatu, and Serra Geral formations. The contacts between the deposits of the Guará and Botucatu Formations and their boundaries between Serra Geral Formation flows demonstrate that these sedimentary environments remained active during the onset of volcanism, and there was no hiatus between these units. Therefore, the Guará and Botucatu Formations present ages between Late Jurassic and Early Cretaceous.