Paper No. 58
Presentation Time: 11:15 PM


SUMPTION, Grace L., Geology and Geological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, 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,

Mapping in the area of Witmarsum, Parana State, Brazil, has identified numerous occurrences of glacially furrowed and striated surfaces on both the Carboniferous Itararè and Devonian Furnas Formations. The goal of this study is to determine if the furrowed units (e.g. the subglacial units) consisted of lithified or soft sediments and if the glacial flow was influenced by preglacial topography. Trends of the striations were taken, and furrow measurements (trough depth, crest elevation, amplitude, period, and bedding orientation) were taken. Rock samples of the striated pavements were taken from five different locations. Samples were cut at 90-degree angles and bedding characteristics will be analyzed under a dissecting microscope.

All samples analyzed were taken from predominantly sandy units. Deformation features such as reoriented or deformed bedding and cross bedding will indicate if the subglacial units were squeezed and molded into the furrow form (e.g. soft sediment deformation). While truncated and undeformed sedimentary structures would suggest erosion by a glacier advancing across a lithified surface. Using topographic maps and Google Earth, streamline forms were located in order to determine if the modern topography is influenced by the pre glacial topography.

Research for this study was funded by a grant from the N.S.F.-R.E.U Program (NSF-EAR-1262945).