Bioestratigrafia do Neopaleozóico da Bacia do Paraná

Neopaleozoic biostratigraphy of the Paraná Basin

Abstract

Surface samples and cores from 31 exploratory wells were chosen as being the most representative among those drilled by Petrobras across the Paraná Sedimentary Basin, from Mato Grosso and Goiás to Rio Grande do Sul. Their analysis yielded a large amount or Saccites, Monoletes and Monocolpates spores, in adition to representatives of Tasmanales. From the great number of identified forms, 40 species – characterized by their wide geographical distribution allied to a short vertical range – were selected and used as a basis for the biostratigraphical subdivision of the Gondwana section of this sedimentary basin. This biostratigraphic column was divided into six main intervals, designated by the let-ters G to L, some with further subdivisions. The comparison of the species with those described from other regions provided sufficient geochronological data for the dating of the different intervals. It also demonstrated that the Upper Paleozoic sedimentary sequence in the Paraná Basin ranges from the Upper Pennsylvanian (Stephanian C) to the Upper Permian (Kazanian). To complete the paleogeologic data the previously established zonation of the Devonian sec-tion was also included. The correlation of the bios-tratigraphic intervals across the basin and their relationship with the rock-stratigraphic units are demonstrated in severaI sections. The interpretation of these sections and of the biostratigraphic interval isopachous maps provided important information on the paleogeographic development of the basin. Among the more significant results is evidence of the start of the Permo-Carboniferous sedimentation in the northern regional depression, of a subsequent southward tilting of the basin accompanied by the progressive advance of the deposits toward the Rio Grande do Sul shield and of a Lower Permian lacuna in eastern Paraná indicating the beginning of the epeirogenic process which culminated with the rise of the Ponta Grossa arch. The paper also presents some paleoecological considerations and the concluding chapter deals with the systematic discussion of the sporomorphs accompanied by illustrati