Mineralogy of pliocene to middle pleistocene red clays in SE Transdanubia (Hungary). review of the quantitative data
Reference:
Acta Mineralogica-Petrographica, Szeged 2006–2007, Vol. 47, pp. 25-46
Szerző:
Viczián István
Abstract:
Red silty clays filling fissures in limestone, karstic depressions and recent caves in the Villány Mts. (SE Transdanubia, Hungary), and Pliocene to Quaternary red clays of the surrounding hilly areas were studied. For comparison also yellow clays and Pannonian basin sediments were investigated. The quantitative mineral composition was determined by X-ray diffraction for the bulk sample and for the <2 µm fraction. For a statistical evaluation in triangular diagrams the data of 181 quantitative analyses of the bulk composition and 129 analyses of the <2 µm fraction were collected. Minerals in the whole rock were sorted into 3 groups according to their genetic significance: (1) carbonates, (2) detrital and slightly weathered minerals and (3) products of strong weathering. The 3 groups for clay minerals in the <2 µm fraction were: (1) illite and chlorite, (2) smectite and vermiculite and (3) kaolinite and gibbsite. Two main associations of minerals could be distinguished. A highly weathered association consisting of the minerals of disordered kaolinite, kaolinite/smectite mixed-layer mineral, smectite and occasionally gibbsite was selected which normally contains Ti-oxides and more hematite than goethite. Quartz contents are low, feldspars are absent. Calcite is high only when secondary cementation or admixture of wall rock fragments occurs. The association represents a weathering crust formed on the karstified surface during a warm and humid climatic period of the Middle Pliocene. The other, more widespread, less weathered association contains well crystallised clay minerals, dominantly illite accompanied by smectite, illite/smectite, chlorite or kaolinite, relatively much quartz and feldspars but little calcite. The typical iron mineral is here goethite. This association represents weakly or moderately weathered terrestrial or shallow basin sediments of Pliocene to Middle Pleistocene age. The genetic conclusions obtained agree well with results obtained by the study of Vertebrate fossils.
acta2006-2007, kaolinite, kaolinite/smectite, karst, Pliocene, Quaternary, red clays, SE Transdanubia, Tengelic Fm.
