Complex evaluation of paleomagnetic and K/Ar isotope data of the miocene ignimbritic volcanics in the Bukk Foreland, Hungary

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Abstract

The joint paleomagnetic and geochronological study of the Bukk Foreland is primarily aimed at providing a time framework for the ignimbritic volcanic evolution of the area, where relevant biostratigraphical data are lacking. Rock samples for paleomagnetic measurements and K/Ar dating were mostly taken from the same sites. The total number of the paleomagnetic sites is 33, and of K/Ar sites 32. K/Ar age determinations were mainly carried out on monomineralic fractions from ignimbrites and pumices; in the case of strongly welded ignimbrites and lithic clasts whole rock was analysed. K/Ar dating indicates that the ignimbritic volcanism of the Bukk Foreland occurred between 21-13.5 Ma. Within this interval three main events can be distinguished: 21.0-18.5, 17.5-16.0 Ma and 14.5-13.5 Ma respectively. They are well separated by paleomagnetic declinations of the respective volcanic products (80°, 30°, 0°, respectively). The resolution is less in the K/Ar data because of the overlapping of the analytical ages. In terms of the areal distribution the 'Lower Ignimbrites' with 80°CCW rotation as well as the 'Upper Ignimbrites' with 30°CCW rotation are widespread. Both measurement methods point to the occurrence of a youngest ignimbritic horizon in a restricted area at the western part of the Bukk Foreland. The significance of the results from a geodynamic point of view is that the large Neogene CCW rotations of the Bukk Foreland are now precisely dated.

Original languageEnglish
Pages (from-to)467-476
Number of pages10
JournalActa Geologica Hungarica
Volume41
Issue number4
Publication statusPublished - Dec 1 1998

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Keywords

  • Bukk Foreland
  • Correlation of Miocene tuff horizons
  • Ignimbrites
  • K/Ar dating
  • Paleomagnetism

ASJC Scopus subject areas

  • Geology

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