RADIOMETRIC DATING OF THE TERTIARY VOLCANICS IN LOWER SILESIA, POLAND. III. K-Ar AND PALAEOMAGNETIC DATA FROM EARLY MIOCENE BASALTIC ROCKS NEAR JAWOR, FORE-SUDETIC BLOCK
Krzysztof BIRKENMAJER (1), Zoltán PÉCSKAY (2), Jacek GRABOWSKI (3), Marek W. LORENC (4) & Paweł P. ZAGOŻDŻON (5)
1) Institute of Geological Sciences,
Polish Academy of Sciences, Cracow Research Centre, Senacka 1, 31-002
Kraków, Poland; e-mail: ndbirken@cyf-kr.edu.pl
2) Institute of Nuclear Research, Hungarian
Academy of Sciences, Bem tér. 18c, 4001 Debrecen, Hungary; e-mail: pecskay@moon.atomki.hu
3) Polish Geological Institute, Rakowiecka
4, 00-975 Warszawa, Poland; e-mail: jgra@pgi.waw.pl
4) Institute of Geological Sciences, Polish
Academy of Sciences, Sudetic Geology Department, Podwale 75, 50-449
Wrocław; e-mail: mwlorenc@twarda.pan.pl
5) Faculty of Mining, Wrocław University of
Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland e-mail:
Pawel.Zagozdzon@ig.pwr.wroc.pl
Birkenmajer, K., Pécskay, Z., Grabowski, J.,
Lorenc, M. W. & Zagożdżon, P. P., 2002. Radiometric dating of the
Tertiary volcanics in Lower Silesia, Poland. III. K-Ar and palaeomagnetic
data from Early Miocene basaltic volcanics near Jawor, Fore-Sudetic
Block. Annales Societatis Geologorum Poloniae, 72: 241-253.
Key words: K-Ar dating, basaltic rocks (basanite, olivine basalt),
palaeomagnetism, Early Miocene (Aquitanian, Burdigalian), Lower Silesia,
Poland.
Abstract: The K-Ar dating of Tertiary basaltic rocks near Jawor, Lower Silesia (Poland), included the sites at Winna Góra (plug) and at Męcinka (lava flow, and vent/dyke), well exposed in working quarries. According to new geochemical data, these rocks, classified so-far as trachyandesites, have been reclassified as basanite and olivine basalt. Early Miocene (Aquitanian) K-Ar ages, have been obtained from the basanite lava flow at Męcinka (21.05±0.85 Ma), and from the basanite plug at Winna Góra (21.62±0.93 Ma, and 21.96±1.36 Ma, respectively). An olivine basalt vent/dyke which cuts the lava flow at Męcinka yielded a younger (Burdigalian) K-Ar age (18.66±0.82 Ma). New palaeomagnetic analysis confirmed the results of previous studies that these rocks were magnetized during a reversed regime of geomagnetic field. The basanite (plug and lava) K-Ar dates spread over reversed parts of the magnetozones C6A and C6B. A significantly younger K-Ar date from olivine basalt intrusion might be correlated either with the C5D or the C5E magnetozones.
Manuscript received 25 June 2002, accepted 19 November
2002
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