RECONSTRUCTION OF THE PRE-GLACIAL LATE PALEOZOIC LANDSCAPE OF THE WITMARSUM AREA, PARANÃ STATE, BRAZIL USING GIS

Mapping and the analysis of glacial features of the Late Paleozoic Itararé Subgroup; Witmarsum area, Paraná State, Brazil; indicates multiple advances of the Paraná Glacial Lobe into the southeastern portion of the Paraná Basin. Striae on bedrock (Devonian Furnas Formation) and soft sediment glacial furrows on multiple substratum in the Itararé Subgroup (Carboniferous) suggest that ice flow directions varied both geographically and temporally. The goal of this project was to determine the influence of preglacail topography on Late Paleozoic glacial flow and to reconstruct the pre-glacial landscape.

For this study, exposures of the pre-glacial bedrock surface and stratigraphic horizons within the Itararé Subgroup were located, described and elevations were recorded. If glacially sculpted, elongate features (striae or furrows) were present they were described and their orientations were measured. The data collected was then entered into a database format and maps showing striae and furrow location and directions were generated using ArcGIS software. Additionally a triangulated irregular network (TIN) that models the pre-glacial topography was generated using the modern elevation values for each of the pre-glacial outcrop locations.

Evaluation of the reconstruction of the pre-glacial topography of the Witmarsum area indicates a topographic low (possibly a valley or fiord) was present in the area. Maps of striae and furrow trends suggests that this topographic low may have influenced glacial flow during the Itararé Subgroup glacial advances. However, more data are needed to increase the resolution of the geodatabase and maps created and to determine the magnitude of offset by post glacial tectonism.

Research for this study was funded by a grant from the N.S.F.-R.E.U. Program (NSF-EAR 0640575).