Northeastern (46th Annual) and North-Central (45th Annual) Joint Meeting (20–22 March 2011)

Paper No. 16
Presentation Time: 8:00 AM-12:00 PM


PAULS, Kathryn N., Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave, Milwaukee, WI 53201, ROCHA-CAMPOS, A.C., Instituto des Geosciências, Universidade de São Paulo, Sao Paulo, 05450-001, Brazil and COTTER, James F.P., Geology Discipline, University of Minnesota, Morris, 600 East 4th Street, Morris, MN 56267,

Late Paleozoic sedimentary units of the Paraná Basin located in southern Paraná State, Brazil, range in age from Devonian (Furnas Formation) to early Permian (Itararé Subgroup). The Furnas Formation consists of cross-bedded, predominantly quartz sandstones which formed as a fluvial or deltaic, shallow marine unit. During the Permian, the São Paulo lobe of the Gondwana ice sheet overrode the Furnas Formation, leaving behind an alternating sequence of sandstone and diamictite, which is now collectively called the Itararé Subgroup.

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.