JpGU-AGU Joint Meeting 2017

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[JJ] Oral

S (Solid Earth Sciences) » S-VC Volcanology

[S-VC50] [JJ] Volcanic and igneous activities, and these long-term forecasting

Sat. May 20, 2017 9:00 AM - 10:30 AM A04 (Tokyo Bay Makuhari Hall)

convener:Teruki Oikawa(Institute of Earthquake and Volcano Geology, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology), Takeshi Hasegawa(Department of Earth Sciences, College of Science, Ibaraki University), Daisuke MIURA(Geosphere Sciences, Civil Engineering Research Laboratory, Central Research Institute of Electric Power Industry), Nobuo Geshi(Geological Survey of Japan, The National Institute of Advanced Industrial Science and Technology), Chairperson:Hiroyuki Hoshi(Department of Earth Sciences, Aichi University of Education), Chairperson:Kuniyuki Furukawa(Faculty of Business Administration, Aichi University)

9:45 AM - 10:00 AM

[SVC50-04] Flow directions of Miocene pyroclastic flow deposits on the northern Kii Peninsula, Japan, inferred from AMS (anisotropy of magnetic susceptibility) measurements

*Hiroyuki Hoshi1, Masanori Ito1 (1.Aichi University of Education)

Keywords:AMS (anisotropy of magnetic susceptibility), pyroclastic flow deposits, flow direction, Miocene, Kii Peninsula

The northern part of the Kii Peninsula in central Japan was hit by a massive, widespread pyroclastic flow sometime between 15 and 14 Ma. This is based on the presence of the middle Miocene Muro pyroclastic flow deposit and its correlated deposits. To investigate the flow direction, we measured the anisotropy of magnetic susceptibility (AMS) of rock samples (n = 350) collected from 37 sites in these deposits. The samples are composed of rhyolitic-dacitic tuff (mostly welded). In general, the degree of anisotropy is not so high and the magnetic fabric is dominated by oblate (disk-like) shapes. Magnetic foliation and lineation data for the Muro pyroclastic flow deposit suggest that the flow direction as a whole was south to north but was not uniform on a local scale. Our AMS results imply a source pyroclastic vent (or vents) located to the south of Muro.