A correlation between plant zones and palynozones within a sequence-stratigraphic framework for the upper Paleozoic rocks of the Paraná Basin, Brazil, is attempted for the first time. Our study indicates that (1) the stratigraphic boundaries (lithostratigraphic boundaries and sequence boundaries) are not coincident with most of the biostratigraphic horizons; (2) the boundaries between palynozones and plant zones are also not coincident with each other; and (3) the boundaries of palynozones lie near the maximum flooding surfaces through the interval analyzed. The emerging pattern suggests that plant zones are mostly controlled by depositional processes and palynozones by climate-driven changes. Therefore, the plant zones correspond to distinct ecofacies, and are better regarded as ecozones rather than as biozones. On the other hand, the climatic changes that affected the palynofloras were related directly to the most significant transgressive events, suggesting a link with eustatic oscillations caused by Early Permian Glacial-Interglacial Phases. Aims of further work may include (a) evaluation of taphonomic controls in plant-bearing beds, (b) better understanding of the relation between the plant-bearing strata and their equivalent palynologic zones, (c) correlation between palynologic and paleobotanic data and the sequence-stratigraphic framework already established in other areas, and (d) improvement of the chronostratigraphic chart of the basin through the discovery of layers suitable for radiometric dating.

The Bashkirian to Sakmarian-Artinskian Itararé subgroup provides a record of the evolution of the Permian-Carboniferous glaciation in the Paraná Basin (Brazil). The glaciogenic succession was deposited under the influence of glaciers incoming from southwestern Africa. This paper presents an overview of the third-order sequence stratigraphy of that succession and a biostratigraphic summary, showing that: (1) the most complete and thick outcrop portion of the glaciogenic succession occurs in the northeastern part of the Paraná Basin, where several (at least nine) major cycles of ice advance and retreat can be recognized during the development of the Itararé subgroup; (2) biostratigraphically, two well-defined stratigraphic gaps within the Permian-Carboniferous succession are recognized, one within the Itararé subgroup, related to the Lapa–Vila Velha incised valley fill, and another at the Itararé–Rio Bonito boundary, both of which represent regional sequence boundaries; and (3) the transition between palynozones Crucisaccites monoletus and Vittatina costabilis is associated with the maximum flooding surface represented by the marine Lontras Shale, a regional marker bed located in the upper third of the glaciogenic succession.

Abstract The coal-bearing Early Permian succession of the Paraná Basin in southernmost Brazil is linked to a third-order depositional sequence, where the most important coals occur in the initial transgressive systems tract. In the Candiota area, the main coal zone consists of 17 seams, which were analyzed for petrographic properties (macerals, gelification index, tissue-preservation index, vitrinite reflectance). These results are compared to the high-resolution sequence-stratigraphic framework to enhance our understanding of the stratigraphic controls on coal formation, coal distribution, and coal quality, providing guidelines for optimal exploitation. The results show that local changes in accommodation trends and high sediment influx practically preclude coal formation in the lowstand and highstand systems tracts, whereas major coal development occurred in the transgressive systems tract. Seam distribution and thickness are controlled directly by flooding events, as depicted by the parasequences mapped in the study area. The main variations in thickness and extent occur at, or close to, the parasequence bounding surfaces. The most important coals, which are as much as 2.50 m in thickness, occur in the initial transgressive systems tract. Coal petrographic parameters suggest an overall drying-upward trend in the coal seams developed in the upper part of third-order sequence 2, with significant differences of coal properties relative to their stratigraphic position between and within the parasequences. Detailed petrographic analysis of seam subsections indicates a transgressive nature for the thick coal seams occurring in parasequence 4 (CCI and CCS seams). These are characterized by decreased vitrinite reflectance at the base and top of the coal seams. The high inertinite content of the overlying BL seam at the top of PS 4 suggests accumulation of the precursor peat in a regressive phase of the parasequence.