Intermediate field directions recorded in Pliocene basalts in Styria (Austria): evidence for cryptochron C2r.2r-1

Abstract

Pliocene volcanic rocks from south-east Austria were paleomagnetically investigated. Samples were taken from 28 sites located on eight different volcanoes. Rock magnetic investigations revealed that magnetic carriers are Ti-rich or Ti-poor titanomagnetites with mainly pseudo-single-domain characteristics. Characteristic remanent magnetization directions were obtained from alternating field as well as from thermal demagnetization. Four localities give reversed directions agreeing with the expected direction from secular variation. Another four localities of the Klöch–Königsberg volcanic complex (3) and the Neuhaus volcano (1) have reversed directions with shallow inclinations and declinations of about 240° while the locality Steinberg yields a positive inclination of about 30° and 200° declination. These aberrant directions cannot be explained by local or regional tectonic movements. All virtual geomagnetic pole positions are located on the southern hemisphere. Four virtual geomagnetic poles lie close to the geographic pole, while all others are concentrated in a narrow longitude sector offshore South America (310°–355°) with low virtual geomagnetic pole latitudes ranging from − 15° to − 70°. The hypothesis that a transitional geomagnetic field configuration was recorded during the short volcanic activity of these five localities is supported by 9 paleointensity results and 39Ar/40Ar dating. Virtual geomagnetic dipole moments range from 1.1 to 2.9·1022 Am2 for sites with low VGP latitudes below about 60° and from 3.0 to 9.3·1022 Am2 for sites with higher virtual geomagnetic pole latitudes. The new 39Ar/40Ar ages of 2.51 ± 0.27 Ma for Klöch and 2.39 ± 0.03 Ma for Steinberg allow for the correlation of the Styrian transitional directions with cryptochron C2r.2r-1 of the geomagnetic polarity time scale. Graphic abstract

On the Effect of Shield Friction in Hard Rock TBM Excavation

“…LimestoneKanzelkalk (Graz Paleozoic) Quarry "Kanzelsteinbruch Gratkorn GmbH" e.g.,(Flügel 2000) Basalt Pliocene intrusion, Styrian Basin Quarry "ALAS Klöch GmbH" e.g.,(Gross et al 2007;Schnepp et al 2021) Granite Brixner Granite Brenner Base Tunnel-BBT SE, South Tyrol e.g.,(Brandner et al 2008;Sander 1906) Quartz phyllite Innsbrucker Quartzphyllite Brenner Base Tunnel-BBT SE, North Tyrol e.g.,(Brandner et al 2008;Haditsch and Mostler 1982) …”