Lithostratigraphy of the Serra Geral Formation in the northern portion of the Paraná-Etendeka Igneous Province: A tool for tracking Early Cretaceous paleoenvironmental changes

Abstract

A detailed lithofacies analysis in Continental Flood Basalt Provinces allows the comprehension of their evolution and paleoenvironmental significance. In the northern portion of the Paraná-Etendeka Igneous Province (PEIP), in Brazil (Uberlândia-Araguari area), a volcanological and stratigraphic approach provided evidence that the basaltic volcanic succession is not monotonous, involving different lava flow morphologies and architecture. The volcanic succession reaches a thickness of ca. 300 m and includes four lithofacies associations: pillow lavas, compound pahoehoe, simple pahoehoe, and sediment-matrix basalt breccia. Pillow lavas, simple pahoehoe, and compound pahoehoe characterize the onset of volcanic activity in the area. Sediment-matrix basalt breccia and thick simple pahoehoe lavas occur in upper stratigraphic levels. Some of these thick igneous bodies can represent invasive lavas or shallow intrusions. In the study area, the common presence of volcanic deposits and structures formed in wet conditions is evidenced by the occurrence of pillow lavas, undulatory columns, and interleaved lacustrine and fluvial sedimentary rocks. These deposits reflect different environmental conditions from those previously described as arid in other portions of the PEIP. Low-temperature post-depositional alteration has affected the volcanic and sedimentary rocks of the study area, obliterating many of the primary sedimentary structures. The subaerial and subaqueous lavas are chemically similar, and compatible with high-TiO2 Pitanga magma type. The Uberlândia-Araguari area and the southern part of the PEIP have a similar stratigraphic style both characterized by the dominance of compound pahoehoe lavas at the base and by an intermittent volcanism, which is evidenced by the intercalation of sedimentary deposits with lavas.