Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Oral

S (Solid Earth Sciences) » S-EM Earth's Electromagnetism

[S-EM17] Geomagnetism, Paleomagnetism and Rock Magnetism

Mon. May 21, 2018 10:45 AM - 12:15 PM A03 (Tokyo Bay Makuhari Hall)

convener:Nobutatsu Mochizuki(Priority Organization for Innovation and Excellence, Kumamoto University), Hisayoshi Shimizu(Earthquake Research Institute, University of Tokyo), Chairperson:Hoshi Hiroyuki(Department of Science Education, Aichi University of Education), Mochizuki Nobutatsu(熊本大学)

11:00 AM - 11:15 AM

[SEM17-08] Paleomagnetism and rock magnetism of the upper part of the Miocene Ichishi Group in Southwest Japan

*Hiroyuki Hoshi1, Ryutaro Kuroki2, Hikoma Oshida3 (1.Department of Earth Sciences, Aichi University of Education, 2.Graduate, Aichi University of Education, 3.Aichi Prefectural Kaisho High School)

Keywords:Ichishi Group, magnetostratigraphy, paleomagnetism, rock magnetism, Southwest Japan, tectonic rotation

We present new paleomagnetic and rock magnetic data from an early Miocene sedimentary sequence of the upper part of the Ichishi Group. This study was performed in order to correlate the N7/N8 planktonic foraminiferal zonal boundary, which has successfully been detected in the same sequence, to the magnetostratigraphy. We collected oriented cores at 33 sites on a measured stratigraphic section. Analysis of stepwise demagnetization data allow us to determine site-mean characteristic remanent magnetization (ChRM) directions for 26 sites that display a reverse-normal-reverse (R-N-R) stratigraphic change of magnetic polarity. Our results show that the N7/N8 zonal boundary is located within the upper reverse polarity zone, and this magneto-biostratigraphic correlation is consistent with GTS2004 rather than GTS2012 (GTS = Geologic Time Scale). The reliable site-mean directions have a consistently northeasterly declination, indicating ~40° clockwise rotation.