Volcanic stratigraphy of the high-Ti basalt succession in the northern Paraná Magmatic Province based on geochemistry of detailed field sections in the Jaú-Barra Bonita region

Abstract

We combined detailed field work with whole-rock geochemistry of samples from both surface exposures and rock chips from a ~300 m pile of basalt retrieved from a groundwater borehole in the Jaú region (central part of the state of São Paulo) to contribute to the stratigraphic knowledge of the northern Paraná Magmatic Province. The P₂O₅ content was used as the first guide to flow identification, always combined with other minor and trace elements (mostly Ti, Zr, Sr, and Cu). This approach allowed the establishment of a stratigraphic column with 16 flows, which were tentatively divided into three sequences. Regional correlations show that the lower portion of these basalt flows (Sequence 1) has good correspondence with the flow-by-flow succession identified at the border of the Paraná Basin by previous regional works. The upper eight flows, occurring at the top of the plateau where the thickness of basalt reaches up to 300 m, should have their continuity westward (toward the center of the Paraná Basin), where the volcanic pile thickens. The local preservation of these upper flows may result from significant (up to 170 m) displacements along the ENE-directed Jaú fault, identified from stratigraphic relations here defined in the basalt pile.

KEYWORDS:
volcanic stratigraphy; Paraná Magmatic Province; Serra Geral Group; geochemistry