Terrestrial Kaolin Deposits Trapped In Miocene Karstic Sinkholes On Planation Surface Remnants, Transdanubian Range, Pannonian Basin (Hungary)

In the Transdanubian Range, Pannonian Basin, Hungary, karstic sinkholes on a planation surface of Triassic carbonates are filled by grey clayey-silty kaolin deposits. The provenance and accumulation age of these strongly altered terrestrial karst-filling sediments are constrained by X-ray powder diffraction, heavy mineral analysis and zircon U-Pb dating. The heavy minerals of the Southern Bakony Mountains samples are dominated by the ultra-stable zircon-rutile-tourmaline association. Zircon U-Pb data indicate accumulation between 20 and 16 Ma. Furthermore, Archaean to Palaeogene grains were also determined, reflecting the principally fluvial recycling of Eocene bauxites and their cover sequences. In contrast, the sample from the Keszthely Hills consists almost exclusively of airborne material including zircons of 18-14 Ma, reflecting a dominant contribution from the Carpathian-Pannonian Neogene volcanism. The shift in the Miocene age components is inferred to have been caused by the landscape evolution and burial history of the planation surface remnants controlled by local block tectonics.