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The Bauxites of the Northern Margin of the Dinarides Carbonate Platform (Area of Jajce, Bosnia)

The northern, i.e. the northeastern margin of the Mesozoic carbonate platform of the Dinarides represents its external marginal part and marks the boundary zone between the ancient shellow-marine and deep basinal realm in this part of the Mediterranean Tethys. Considerable change in structural relations along the margin started in the Early Cretaceous and induced the longlasting local emergence. Consequentlly, the land area formed arranged in two separated island chains, i.e. the inner and the outer island chain. On the exposed land surfaces paleokarst morphology rapidly formed. A parent bauxite material that was subsequently turned into bauxite accumulate in depressions on karstified paleorelief. The bauxite deposits on the outer island chain are underlain by different type of shallow-marine limestones of the Aptian-Albian age while on the inner island chain the underlying rocks are represented by limestones of the Cenomanian age. Hence, the deposits are formed within the two paleogeographic provinces. They differ in size and chemical composition. The deposits of the outer island chain are huge, of boehmite type with high Al2O3 and low SiO2 content that make them of considerable economic interest. The deposits of the inner island chain are small and with higher SiO2 content that make them economicaly uninteresting. The different characteristics of the two bauxite provinces are most probably due to the longer duration of emergence on the outer than on the inner island chain. The reconstruction of paleogeographic relations during the time of bauxite accumulation suggests the eolian transport for the bauxite parent material.

bauxites; Mesozoic carbonate platform; Cretaceous; Dinarides; stratigraphic position

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