Indication of geohazard risk and economic value of gypsum deposits in the Tertiary Sivas Basin (Turkey) using ASTER and Landsat ETM+ images

The Tertiary Sivas Basin contains widespread, tectonically deformed deposits of massive Oligocene gypsum. This unit is one of the most important factors controlling the tectono-stratigraphic evolution of the basin insofar as these deposits are interpreted as decollement levels. Sivas Basin also has remarkable structural expressions within these evaporite deposits, as seen in satellite images aided by colour composites. Because of the arid climatic conditions of the region, the basin provides ease of interpretation geologically in terms of the synoptic-view capability of broad-band multispectral data sets, such as ASTER and Landsat ETM+. In this study, data fusion and decorrelation stretching methods were applied to highlight Oligocene gypsum deposits of the basin. These continental deposits host celestite and barite mineralization of great industrial importance. These gypsum deposits also carry a geohazard impact, namely their propensity to lead to collapses, particularly on the eastern side of the city of Sivas. Because the present study aids in the discrimination of these gypsum occurrences from other geological units, it may also lead to geohazard-risk reduction.