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

Abstract

Datowanie radiometryczne trzeciorzędowych wulkanitów Dolnego Śląska. III. Daty K-Ar i wyniki badań paleomagnetycznych dolnomioceńskich skał bazaltowych okolic Jawora (Blok Przedsudecki) The K-Ar dating o f 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 o f 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.