Acta Musei Moraviae

The Cenozoic sediments in the Holedná game reserve and their significance for archaeology

The Cenozoic sediments partially cover crystalline rocks in the area of Holedná game reserve (Brno town, South Moravia). Holocene to Pleistocene eluvial and/or slope sediments and relics of Ottnangian (Lower Miocene) sediments fill the wide valley to a depth of up to 20 m on the western slope of the Holedná Hill (391 m.a.s.l.). Several landslides were documented in these sediments based on the movement of the fortification wall from the Late Bronze Age. Blocks of limonite-rich sediment situated on the western slope of Holedná Hill (391 m.a.s.l.) were spatially related to the Cenozoic sediments. Sand to silt fraction in the iron oxohydroxides matrix consists of quartz, feldspar and mica. According to the geochemistry, we interpret these sediments as a mixture of the material from at least two sources: products of Neogene lateritic weathering rich in iron oxo-hydroxides (Fe₂O₃ 76.2 wt. %) and continental Ottnangian sediments (sand- and silt-rich layers). In terms of their origin, the Ottnangian sediments in the vicinity of Brno town remain a contro versial problem. These sediments are predominantly continental, with clastic materiál originating from local sources (the transport distance from several kilometres up to tens of kilometres).