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Yamada, Kunimi; Yasue, Kenichi; Iwano, Hideki*; Yamada, Ryuji*; Umeda, Koji; Omura, Kentaro*
Chishitsugaku Zasshi, 118(7), p.437 - 448, 2012/07
Fission-track analyses for samples corrected from around the Atera fault indicated 2 conclusions. The dip-slip displacement of the Atera fault after Cretaceous is about 1 km. It is similar to the displacement of basement rocks or topography across the fault. These are consistent with previous studies that indicated the present Atera fault activity began after late Pliocene. The fracture zone along the fault was widely heated at about 20 Ma. It indicates that the fracture zone existed at the time and perhaps the paleo fault activity has already begun.
Yamada, Kunimi; Yasue, Kenichi; Iwano, Hideki*; Yamada, Ryuji*; Umeda, Koji; Omura, Kentaro*
no journal, ,
no abstracts in English
Sato, Toshinori; Kiguchi, Tsutomu*; Itamoto, Masaharu*; Omura, Kentaro*
no journal, ,
no abstracts in English
Ogata, Manabu; King, G.*; Herman, F.*; Sueoka, Shigeru; Yamada, Ryuji*; Omura, Kentaro*
no journal, ,
no abstracts in English
Ogata, Manabu; King, G. E.*; Herman, F.*; Sueoka, Shigeru; Yamada, Ryuji*; Omura, Kentaro*
no journal, ,
no abstracts in English
Ogata, Manabu; King, G. E.*; Herman, F.*; Yamada, Ryuji*; Omura, Kentaro*; Sueoka, Shigeru
no journal, ,
Optically stimulated luminescence (OSL) thermochronometry is a tool for constraining cooling histories in low-temperature domains (several tens of degree Celsius) during the past 10-100 kyr. This method is currently applied only to rapidly denuded regions (about 5 mm/yr), because luminescence signals in slowly denuded regions saturate before the rocks are exhumated to the surface. However, cooling histories in slowly denuded regions may be constrained if unsaturated samples are obtained from deep boreholes. We applied multi-OSL-thermochronometry to the deep borehole core drilled at the Rokko Mountains, Japan, where slow denudation rates (0.1-1.0 mm/yr) are expected from previous studies. We used the Kabutoyama core collected by National Research Institute for Earth Science and Disaster Resilience. The total length of Kabutoyama core is 1,313 m and we collected the samples at 408, 642, 818 and 1048 m for OSL-thermochronometry. We found that the sample temperatures remained around the present ambient temperature at each depth for the last 0.1 Myr, indicating that the Rokko Mountains is topographically stable, which was consistent with previous findings. Thus, the thermal denudation history of slowly denuded regions may be constrained by multi-OSL-thermochronometry using samples from deep borehole cores. However, the denudation rates in the Rokko Mountains were too low and could not be determined by this method.
Ogata, Manabu; King, G. E.*; Herman, F.*; Yamada, Ryuji*; Omura, Kentaro*; Sueoka, Shigeru
no journal, ,
Optically stimulated luminescence (OSL)-thermometry can be used to reconstruct the thermal structure in slowly denuded regions where infrared stimulated luminescence (IRSL) signals of samples obtained from deep boreholes are measured and evaluated with depth. Only one study had explored this approach, using a target mineral of Na-feldspar. We applied multi-OSL-thermometry to K-feldspar obtained from deep borehole core samples drilled at the Tono (MIZ-1) and Rokko regions (Kabutoyama), which are well-documented thermally stable crustal environment. For the K-feldspar obtained from the MIZ-1 core, the inverted temperatures for the IRSL50 
C of the samples at a depth of 
1 km (40 C) were consistent with the in-situ temperatures. The results suggest that the application of OSL-thermometry to K-feldspar in a borehole is useful to reconstruct the palaeothermal condition. In this presentation, we will also show the results of the Kabutoyama core to draw more comprehensive conclusions.
