International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

40Ar/39Ar dating of Miocene tuffs from the Styrian part of the Pannonian Basin: an attempt to refine the basin stratigraphy

Pages: 483 - 494

Authors: ROBERT HANDLER,, FRITZ EBNER, FRANZ NEUBAUER, ANA-VOICA BOJAR, SIEGFRIED HERMANN

Abstract: In this study we present new 40Ar/39Ar age data obtained from volcaniclastic material intercalated within shallow-marine to neritic sediments of the Styrian part of the Miocene Paratethyan Sea, which allow a better control of the sedimentation. At Retznei quarry, a volcaniclastic layer has been deposited in erosional patches above a consolidated rhodolite limestone (“Leitha Limestone”) of the siliciclastic/marine Badenian Weissenegg Formation. Ar-release plots of a biotite bulk-grain concentrate (30 grains) and a concentrate of three sanidine crystals (0.5–1 mm) display fairly flat release-patterns with minor fluctuation in the low-energy gas-release steps. From the statistical point of view the biotite concentrate yielded a high-precision plateau age of 14.21±0.07 Ma, the three sanidine crystals yielded a plateau age of 14.39±0.12 Ma. The radiometric ages obtained match the biostratigraphic record (Upper Lagenide Zone). A drill-core recovered from the well Hörmsdorf, exposes several sand-dominated horizons and two layers of crystal tuff, of the Karpatian Eibiswald Formation. Ar-analyses of one single biotite grain (> 1 mm) from the hanging-wall, another biotite single-grain from the lower tuff both display slightly disturbed Ar-release spectra. However Ar-plateau ages of 15.08±0.09 Ma and 15.22±0.17 Ma, respectively, have been obtained. Volcaniclastic rocks from Pöls are intercalated within the Florian Formation., for which previous authors suggested a Lower Badenian age (16.4–ca. 15 Ma according to Rögl 1996). A concentrate of two clear sanidine crystals (0.5–1.0 mm), yielded a perfect Ar-plateau recording an age of 15.75±0.17 Ma, which is more precise than previously published K-Ar results.

Keywords: Miocene, Paratethys, Pannonian Basin, volcanism, 40Ar/39Ar step-heating

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Volume 57 no. 6 / December 2006

Volume 57 no. 6