Geochronological correlation of the main coal interval in Brazilian Lower Permian: Radiometric dating of tonstein and calibration of biostratigraphic framework

The radiometric age of 291 ± 1.2 Ma obtained through single-crystal zircon U–Pb ages (Sensitive High Resolution Ion MicroProbe – SHRIMP II) of tonsteins from the Leão-Butiá Coalfield, southern Paraná Basin (Rio Grande do Sul state), associated with previous SHRIMP II radiometric data obtained from tonsteins from the western (Candiota Coalfield) and eastern (Faxinal and Leão-Butiá coalfields) borders of the basin indicate that the mean age of the main peat-forming interval is 291.0 ± 1.3 Ma. In a regional context, the mean age represents a consistent geochronological correlation for the uppermost and more important coal seams in southern Brazilian coalfields, but this assumption does not establish an ash fall origin from a single volcanic event. According to the International Stratigraphic Chart, the interval is dated as middle Sakmarian. The coal palynofloras are included in the Protohaploxypinus goraiensis Subzone within the palynostratigraphic framework for the Brazilian Paraná Basin. Formal relationships are also established with the Glossopteris–Rhodeopteridium Zone within the phytostratigraphic chart for the Lower Permian of southern Brazilian Paraná Basin.