DISTINGUISHING BETWEEN THE SAND UNITS OF THE CARBONIFEROUS ITARARé SUBGROUP AND THE DEVONIAN FURNAS FORMATION IN PARANA STATE, BRAZIL

Late Paleozoic glacial deposits of the Itararé Subgroup in the Paraná Basin, southern Brazil were generated during multiple advance-retreat phases of the Gondwanan ice sheet. The resulting glacigenic sediments were deposited on a glacially produced erosional contact with the Devonian Furnas Formation. The Carboniferous Itararé Subgroup contains interbedded layers of diamictite and sandstone (quartz arenite) and overlies cross-bedded sandstones (quartz arenites) of the Devonian Furnas Formation. Sandstones from both the Itararé and the Furnas are similar in hand sample and are difficult to distinguish from one another in the field. Normal faulting of horizontal stratigraphy in the Witmarsum area of Paraná State, southern Brazil as well as the different advance-retreat phases within the Itararé Subgroup makes mapping of these units difficult. This study focuses on distinguishing between the sandstones of the Furnas Formation and the sandstones of the Itararé Subgroup. Samples were collected from known field exposure locations of the Itararé Subgroup and Furnas Formation as well as drill core into the Furnas Formation. Both point counting of disaggregated sandstone samples (2 phi size) and SEM imaging of the grains were used to differentiate the sandstones. While the sandstones are similar in grain size and sorting, differences where noted. The Itararé Subgroups sand grains appear more weathered than the Furnas sand grains. Additionally, the Itararé sands contain greater amounts of lithics than the Furnas sands. Research for this study was funded by a grant from the N.S.F.-R.E.U Program (NSF-EAR 0640575).