K-T境界における粘土鉱物の特異性とイリジウム

概要

論文の詳細を見る
Spherical heating-shocked mica clays are found in Cretaceous-Tertiary (K-T) boundary sediments in the eastern district of Hokkaido, northernmost Japan. The K-T boundary sediments contain relatively high Ir concentrations suggesting an asteroid struck the Earth and caused mass extinctions at the end of the Cretaceous. Foraminifera are totally absent in the grayish black clay. Mineralogical investigations of the claystone have been carried out by the use of X-ray powder diffraction, high resolution electron microscope, energy dispersive spectrometer and heavy-iron Rutherford scattering. Singularity of clay minerals of a continuous stratigraphic section spanning the K-T boundary reveals that the spherical interstratified clay in < 2μm fraction are largely decomposed. The spherical clay shows characteristic stacking disorder of 14A, 10A, 7A phase, which is suggested to be heating events in the K-T boundary.
日本粘土学会の論文
1992-07-25