WEATHERING PRODUCTS ON GRANITES IN THE PIRIN MOUNTAIN - TYPOLOGY AND AREAL DISTRIBUTION

Rock weathering in high mountain areas at temperate latitudes is considered to be a result of vertical climate zonation interacting with geological structures. In this article, both were taken into account in order to study weathering products in granites in the Pirin Mountain. The whole territory was divided into three geomorphic zones: high-, mid- and low-elevation slopes. Eleven test sites have been selected within these three zones, including weathered rock outcrops and grussified profiles. As the weathering products in Pirin have not been reported before, this study provides first results from this area. Grain size, mineralogical analysis and X-Ray Diffraction (XRD) showed that weathering in Pirin occurs mostly in the mid-elevation zone, which is related to the planation levelling during the Late Miocene and the Early Pliocene. Deep weathering profiles of saprolites with primary minerals transformed into kaolinite were only found on slope breaks and in the Popovi livadi pass where soil formation reaches 2 m depth. Apparently, within the high-elevation zone weathering is mostly controlled by the cold climate and mineral transformations reach only to chemical change of micas to chlorite. Considering the Pleistocene's glaciers retreat before 10 000 BP, this weathering level and the depth to around 1 m is regarded as impressive for this altitude. In the low-elevation zone the inherited relief does not favour the formation of fiat sections and the development of deeper grus profiles. Increased slopes are shortening the weathering profiles and chemical changes in primary minerals also only reach to the transformation of mica to chlorite.