Chemical weathering intensity of the Late Cenozoic “Red Clay” deposits in the Carpathian Basin

Abstract

INTRODUCTIONVery little work had been previously done on thistopic in Hungary. In the past decade, little attention hasbeen paid to the red clay in the Carpathian Basin. Dif-ferent views on the formation, properties, and distribu-tion of red clays have been published by severalauthors. Many geologists draw parallels between redclays and bauxites [1–3]. Complex investigationsincluding geology, geomorphology, mineralogy, andgeochemistry were carried out by only a few authorslike Schweitzer and Szo r [4] and Kovacs [5].The most significant progress made on the red clayresearch worldwide is that sedimentology, geochemis-try, geomorphology, and the field survey all demon-strate a wind-blown origin for the red clay [6–9], likethe overlying Pleistocene and Holocene loess. Further-more chemical weathering was studied using geochem-istry [10–13].Important key formations in the Late Cenozoicstratigraphy are the red (silty) clays in the CarpathianBasin. Litho-, bio-, chemo-, and magnetostratigraphicdata show that they were formed in different periods [4,5]. The youngest red paleosol (or reddish clay) is ofEarly Pleistocene age. The older one (red clay) wasformed in the Early and Middle Pliocene [4, 5, 14, 15].This paper deals with the geochemical analysis ofthe red clay formation in the Carpathian Basin and eval-uates chemical weathering intensities.MATERIALS AND METHODSThe investigated sections selected for this study arelocated mainly on the foothills of Hungarian mountains(Fig. 1). These sections are of Pliocene and Early Pleis-tocene age [4, 5, 14, 15]. It consists mainly of threetypes of sediments from upper to the lower: Quaternaryloess–paleosol sequence, Pliocene red clay sequence,and sand or sandy sediments (Fig. 2). Geochemicalanalyses were carried out on 50 samples from 15 redclay sequences from the northern, the southern, and thewestern part of Hungary (Fig. 1). All samples were