AN ANALYSIS OF TWO LATE PALEOZOIC SANDSTONES OF THE PARANÁ BASIN IN SOUTHERN BRAZIL
In the field, it is difficult to distinguish the sandstones of the Itararé Subgroup from the Furnas Formation. Additionally, stratigraphic sequences are difficult to correlate between exposures. A further complication is faulting that occurred in the southeastern portion of the basin during the breakup of Gondwana. The location and extent of the faulting has not yet been fully studied.
Samples were previously analyzed using scanning electron microscope (SEM) photos as well as a grain point count. The goal of the previous study was to determine and characterize the differences between the Furnas and Itararé sandstones. The goal of this current study is to identify two unidentified samples (P18 and P56) from the field. This study uses powder diffraction (XRD) and thin sections to analyze and identify the two samples against other identified samples from the field. These samples were originally hypothesized to be Itararé, but upon further study the XRD results show traces of kaolinite, which appears as lenses within the Furnas. The appearance of kaolinite peaks occurs in most of the samples, and may be due to direct contact by the glacier and subsequent erosion of the Furnas (Trosdtorf et al. 2005). Therefore, the preliminary results indicate that the geology of Witmarsum area needs to be reevaluated. In addition to the detailed stratigraphic mapping of sand units now under way, the extent of faulting and estimates of fault displacement must be assessed in light of new stratigraphic data.