Characterization of the palaeoenvironmental conditions in the Pannonian Basin during the last 34 mys related to the formation of haematitic and kaolinitic sedimentary rocks

Abstract

The Pannonian Basin is a sediment-filled back-arc basin which was formed during the Late Paleogene–Neogene period. Such sedimentary rocks like bauxites or kaolinites, which are important with regard to industry in the region, are the products of former weathering processes. However, our knowledge about the palaeoenvironmental conditions which led to the formation of these mineral resources has not yet been integrated. For this purpose, the former biomes, climatic classes as well as karstification, weathering and paedogenic processes were investigated over the last 34 mys using the southeastern regions of China and the United States as climatically analogous regions. By the second half of the Oligocene, the conditions of intensive chemical weathering ceased to exist in the Pannonian Basin, which enabled the formation of lateritic bauxites during earlier periods. However, up to the mid-Serravallian Stage, intensive karstification as well as the formation of haematite-rich ultisols and alfisols continued when humid subtropical climatic conditions came about. The modelled biomes indicate that aridification during the Early to Middle Miocene led to the formation of less dense vegetation, exacerbating the re-deposition of weathering products. These conditions resulted in the accumulation of haematitic and kaolinitic sedimentary rocks in the fossilized karst depressions. The progressive cooling following the mid-Pliocene decreased the intensity of karstification, moreover, the cessation of humid subtropical conditions brought the sedimentation of haematitic and kaolinitic sedimentary rocks in the Pannonian Basin to an end.