Terrestrial kaolin deposits trapped in Miocene karstic sinkholes on planation surface remnants, Transdanubian Range, Pannonian Basin (Hungary)

István Dunkl,Hilmar Von Eynatten,Gábor Csillag,Ivett Kovács,Andrea Mindszenty,Sándor Józsa,Péter Kelemen

doi:10.1017/s0016756820000515

Abstract

AbstractIn 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.

Highlights

In the Keszthely Hills (KH) and the Southern Bakony Mountains (SBM), kaolin deposits fill ~100 m deep karstic sinkholes of a planation surface formed on Upper Triassic carbonate rocks
This study provides an up-to-date description of the composition, provenance and age of the Cserszegtomaj Kaolin Formation using X-ray diffraction (XRD), heavy mineral analysis and zircon U–Pb geochronology
The XRD, heavy mineral and U–Pb age data reveal major differences of the Keszthely Hills and Southern Bakony Mountains regarding the source of their kaolin deposits, mainly because they developed during different time intervals (Fig. 8a–d)

Summary

Introduction

In the Keszthely Hills (KH) and the Southern Bakony Mountains (SBM), kaolin deposits fill ~100 m deep karstic sinkholes of a planation surface formed on Upper Triassic carbonate rocks. The karstic depressions trapped strongly altered weathering products, such as kaolin, red clay and/or bauxite deposits, from the contemporaneously exposed basement and siliciclastic assemblages (Budai et al 1999; Mindszenty et al 2000). The studied Cserszegtomaj Kaolin Formation (Bohn, 1979; Budai et al 1999) is a yellow, grey terrestrial pelite filling some of the sinkholes in the KH and SBM (Fig. 2). The results obtained from this highly altered terrestrial sediment trapped and preserved in sinkholes proved to be useful in understanding the evolution of carbonate etchplain surfaces (cf Thomas, 2016) in time and space characterized by intense erosion

Geological setting

Materials and Methods

Results

Discussion

Findings

Conclusions