Morphostructural analysis of a tar sandstone area; Paraná Basin; São Paulo.

Abstract

Tar sandstones occur in the Eastern Border of the Paraná Basin, São Paulo State. The occurrences are related to stratigraphical, structural and geomorphological constraints. A morphostructural analysis was performed to establish the relationships between geomorphological features and the geological elements related to tar sandstone genesis. The morphostructural analysis was based on the drainage network map and on remote sensing images. The interpretation has considered the drainage and relief lineaments and the delineation of the main relief flexures. Interpretation is based on the identification of drainage anomalies corresponding to geometric modifications of the regional drainage pattern, such as annular and radial anomalies and asymmetric patterns. Additionally were interpreted linear drainage features with the same length. These features represent joint zones. Many drainage anomalies were detected on the tar sandstone occurrence area, many of them related to geological structures mapped. Thus, the morphostructural map with the delineation of highs and lows and the lineament interpretation are the main geomorphological elements reflecting the geologic factors related to the tar sand occurrence. The occurrences are located in joint zones of high and medium density. Fracture density favors hydrocarbon migration, but also, contradictorily, at different times, erosion of the deposits. The main geological structures in the area, Jacu Structure and Anhembi High, are examples of relationship between geology and relief, helping to explain the genesis of tar sandstones.