Analysis of redox-sensitive trace elements to the reconstruction of the depositional paleoenvironment of the Ponta Grossa Formation in southern Brazil

Abstract

In the Devonian period, several intense climatic changes occurred on Earth, such as global cooling and intense volcanic eruption events, increasing the amount of organic matter in water bodies and forming a bituminous sedimentary material containing redox-sensitive trace elements, called shale. Among the places with this type of rock formation from the Devonian period, one of them is the Ponta Grossa region, located in the Paraná Basin, southern Brazil, which lacks studies that use metals to understand the depositional environment of its formation. Therefore, this study aims to analyze the redox-sensitive trace elements together with the total organic carbon to understand the depositional environment at the time of the formation of these shales. For this, outcrop samples were collected and analyzed regarding the total organic carbon and the redox-sensitive trace elements, generating ratios between them. From the results obtained, it was observed that the environment was warmer and humid, with very low salinity, a greater tendency to anoxia, periods of greater primary productivity, and marine transgressions. Thus, it was possible to know the depositional environment of organic matter that later originated the shale deposits in this region of the planet.