Abstract
From Araraquara to Avare, in the Serra Geral Group outcropping area, 22 detailed geological sections were elaborated. The stratigraphic relationships and the chemical analysis allowed the identification of seven [P 2 O 5 ] basalt classes, all of them pertaining to the Pitanga type, showing a consistent stacking order across the studied region. Thus, each class is considered to correspond to a specific lava flow, allowing a general stratigraphic column to be proposed. Besides the stacking order, the validation of P 2 O 5 as a tool for lava correlation at great distances was also based on the values obtained from samples collected at different positions in a single flow, and on the remarkable [P 2 O 5 ] contrast between adjacent flows. Minimum lateral extensions range from 75 to 185 km, and thickness from 20 to 80 m. Vertical tectonic displacements, which took place in different periods, were inferred from the altitude of specific flows, and also from the Botucatu and Piramboia formations. They are noticeable in a region bounded by EW drainage lineaments, which contains a large area where Piramboia and Botucatu formations crop out, probably due to the tectonic activity causing this region to be a generalized structural high.
Highlights
IntroductionThe use of basalt geochemistry, in order to recognize and correlate individual flows, is based on the concept that primary differentiation is limited during the emplacement of lavas due to rapid emplacement and solidification, and was largely used in classical continental basalt provinces (e.g., Beane et al 1986)
The Geological Institute (IG-SMASP) has carried out a research aiming to evaluate the recharge of the Guarani Aquifer System, through the overlying Serra Geral Group, as recently defined by Rossetti et al (2017)
According to the geochemical criteria of Peate (1997), most samples fit into the Pitanga magma-type; just 3 samples, with low P2O5 (0.22%-0.29%) and TiO2 (
Summary
The use of basalt geochemistry, in order to recognize and correlate individual flows, is based on the concept that primary differentiation is limited during the emplacement of lavas due to rapid emplacement and solidification, and was largely used in classical continental basalt provinces (e.g., Beane et al 1986). It has been demonstrated, in several regions of the Paraná Magmatic Province, that some immobile minor elements, such as Ti and especially P, may be useful “fingerprints” of single basalt flows and effective for correlations
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