[S-EM18] [EE] General Contributions in Geomagnetism, Paleomagnetism, and Rockmagnetism

[SEM18-P05] Reconstruction of paleosecular variation from Lake Biwa sediments: Pass-through measurements and SQUID microscopy

*Hirokuni Oda¹, Yuhji Yamamoto², Yoshio Inouchi³ (1.Institute of Geology and Geoinformation, Geological Survey of Japan, AIST, 2.Kochi University, 3.Waseda University)

Keywords:Scanning SQUID microscope, paleosecular variation, Lake Biwa

We have conducted measurements on one of the three piston cores taken from Lake Biwa off Takashima (BWK12-2; length 1633 cm). Sediment comprises of clay intercalated with at least 13 ash layers. Thirteen horizons were dated with ¹⁴C using plant pieces giving a maximum age estimate of more than 40 ka. Paleomagnetic cube specimens, u-channel samples and LL-channel samples were taken from the core. Paleomagnetic cube specimens were measured with a SQUID Rock Magnetometer at AF demagnetization steps of 0-80 mT. Results of inclination from the cube samples show an agreement with the paleosecular variation reported by Ali et al. (1999). For example, Inclination show a minimum of ~40° at 2600 year BP and a maximum of ~58° at 3400 year BP, both of which can be correlated with a minimum 'h' at 2400 year BP and a maximum 'i' at 2900 year BP presented by Ali et al. (1999), respectively. Pass-through measuremens on u-channel and LL-channel samples were conducted both at Geological Survey of Japan and Kochi Core Center. Paleomagnetic results after deconvolution for u-channel and LL-channel at two different laboratories with different sensor response functions will be compared together with the results of cube samples. Further, a preliminary results measured with a scanning SQUID microscope on some block samples taken from LL-channel samples are going to be presented.