施蒂里亚州（奥地利）上新世玄武岩中记录的中间场方向：隐时C2r.2r-1的证据

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

作者信息

Schnepp Elisabeth, Arneitz Patrick, Ganerød Morgan, Scholger Robert, Fritz Ingomar, Egli Ramon, Leonhardt Roman

机构信息

Palaeomagnetic Laboratory Gams, Chair of Applied Geophysics, Montanuniversität Leoben, Gams 45, 8130 Frohnleiten, Austria.

Conrad Observatorium, ZAMG-Zentralanstalt für Meteorologie und Geodynamik, Hohe Warte 38, 1190 Vienna, Austria.

出版信息

Earth Planets Space. 2021;73(1):182. doi: 10.1186/s40623-021-01518-w. Epub 2021 Oct 3.

DOI:10.1186/s40623-021-01518-w

PMID:34720650

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC8549934/

Abstract

UNLABELLED

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 Ar/Ar dating. Virtual geomagnetic dipole moments range from 1.1 to 2.9·10 Am for sites with low VGP latitudes below about 60° and from 3.0 to 9.3·10 Am for sites with higher virtual geomagnetic pole latitudes. The new Ar/Ar 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.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s40623-021-01518-w.

摘要

未标注

对奥地利东南部上新世火山岩进行了古地磁研究。样本取自八个不同火山上的28个地点。岩石磁学研究表明，磁性载体为富钛或贫钛钛磁铁矿，主要具有准单畴特征。通过交变场以及热退磁获得了特征剩磁方向。四个地点给出的反向方向与长期变化预期方向一致。克洛赫 - 柯尼希斯贝格火山复合体的另外四个地点（3个）和诺伊豪斯火山的一个地点（1个）具有反向方向，倾角浅，磁偏角约为240°，而施泰因贝格地点的倾角为正，约30°，磁偏角为200°。这些异常方向无法用局部或区域构造运动来解释。所有虚拟地磁极位置都位于南半球。四个虚拟地磁极靠近地理极，而其他所有地磁极都集中在南美洲近海的一个狭窄经度扇区（310° - 355°），虚拟地磁极纬度较低，范围从 - 15°到 - 70°。这五个地点短暂火山活动期间记录了过渡性地磁场构型这一假设得到了9个古强度结果和氩 - 氩测年的支持。对于虚拟地磁极纬度低于约60°的地点，虚拟地磁偶极矩范围为1.1至2.9·10²² A·m²，对于虚拟地磁极纬度较高的地点，范围为3.0至9.3·10²² A·m²。克洛赫的新氩 - 氩年龄为2.51 ± 0.27 Ma，施泰因贝格的为2.39 ± 0.03 Ma，这使得施蒂里亚过渡方向与地磁极性时间尺度的隐时C2r.2r - 1相关联。