Insights into organic matter source and depositional environments of shales from the Ponta Grossa Formation in Parana basin, Brazil

Abstract

Marine transgression events and plant species' evolution to terrestrial environments increased the amount of organic matter in sediments during the Devonian Period. Subsequently, a bituminous material known as shale was formed, containing organic compounds that enable the reconstruction of environmental conditions from previous eras. These rock formation events are recorded worldwide, however, in the Ponta Grossa Formation, southern Brazil, a deeper understanding of samples from the Devonian Period is necessary. The goal of this study was to understand the regional environmental conditions, the origin of the organic matter, and the degree of maturation of the bituminous material. Shale samples were collected from an outcrop on the eastern border of the Paraná Basin and processed in the laboratory to obtain the saturated hydrocarbons fraction posteriorly analyzed. The results indicate a poorly oxygenated environment, with various salinity levels, mixed organic sources, and a high thermal maturity of the samples. The analysis of compound hydrocarbons elucidates the environmental conditions during the Devonian Period in the Ponta Grossa Formation, providing inferences applicable to the stratigraphic interval represented by this record and within the domain of the sampled area.