[M-IS18] Drilling Earth Science

[MIS18-P06] Utility of X-ray CT-scanning for biosiliceous sediment cores of the Japan Sea

*Jumpei Yoshioka^1,2, Yusuke Kubo³, Junichiro Kuroda², Arisa Seki⁴, Ryuji Tada^1,5,6 (1.Department of Earth and Planetary Science, the University of Tokyo, 2.Atmosphere and Ocean Research Institute, the University of Tokyo, 3.Koch Institute for Core Sample Research, JAMSTEC, 4.Faculty of Science, Shinshu University, 5.Yunnan University, 6.Chiba Institute of Technology)

Keywords:X-ray CT scan, biosiliceous, physical property, interhole correlation, core disturbance

X-ray CT scanning is a nondestructive method for quantitative analysis of sediment cores. It enables for us to observe interior structures of sediment cores without any damages on the sediment. Sediment cores often have structures such as faults and folds, as well as drilling disturbances, which prevent us from precisely reconstructing paleoenvironment. Bioturbation or burrows are easily visualized, and presence of concretion or nodules can be identified even if they are not on the split surface. Thus, the X-ray CT scanning is a useful tool to visualize sediment structures of cores by using its CT value. The CT value is described as Hounsfield units, which are defined as relative to the attenuation coefficient of water.
The CT value is expected to have a lot of information about physical properties of sediments. We evaluated the relation of the CT value to other physical property data such as gamma ray attenuation, magnetic susceptibility, and color reflectance by using biosiliceous sediment cores taken from International Ocean Discovery Program (IODP) Site U1430 in the Japan Sea. Site U1430 is on the southern upper slope of the eastern South Korean Plateau at 37°54.16’N, 131°32.25’E and 1072 m below sea level. Total recovery lengths of Holes A to C were 258.24 m (94% of penetration), 259.71 m (94%), and 257.02 m (103%), respectively. The sedimentary succession extends from the middle Miocene to the Holocene and is dominated by clayey silt, silty clay, nannofossil ooze, diatom ooze, claystone, and sandstone. The detailed method of the X-ray CT scanning is the same as presented by Tonai et al. (S-CG51 New perspectives of subduction zone earthquake dynamics through experiments across-scales Session). We will introduce the results of the X-ray CT scanning analysis to the biosiliceous sediment at IODP Site U1430 and its implications to physical properties, interhole correlations, and identification of laminated intervals and bioturbated intervals from Miocene through Pleistocene.