Earth Planets Space, Vol. 56 (No. 1), pp. 67-79, 2004
Toru Yada1,2, Tomoki Nakamura1, Nobuo Takaoka1, Takaaki Noguchi3, Kentaro Terada4, Hajime Yano5, Takakiyo Nakazawa6, and Hideyasu Kojima7
1Department of Earth and Planetary Sciences, Graduate School of Sciences, 33 Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan
2Department of Earth and Planetary Science, Graduate School of Science, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3Department of Minerals and Biological Sciences, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512, Japan
4Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
5Department of Planetary Science, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
6Center of Atmospheric and Oceanic studies, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan
7National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo 173-8515, Japan
(Received April 11, 2003; Revised December 26, 2003; Accepted December 29, 2003)
The accretion rate of micrometeorites in the last glacial period was estimated from the concentrations of micrometeorites in the blue ice around the Yamato Mts. in Antarctica. The samples from this study were collected from the five sampling points (M03, K02, K11, J09 and J10) in the blue ice. The blue ice was melted and filtered, and the micrometeorites were handpicked from the collected "glacial sands". The weight of the micrometeorites in the blue ice was estimated from the abundance of recovered micrometeorites and the solar noble gas concentrations in the "residue" after handpicking. The age of the blue ice from the K area was estimated to be 27-33 kyr before present based on oxygen isotope data. The estimated accretion rate to the whole Earth ranges from 5300 103kg/a to 16000 103kg/a. However, the lower end of this range probably represents lower limits due to possible loss of solar noble gases during long residence in the glacier ice. Hence, we estimate that the accretion rate of micrometeorites 27-33 kyr before present to be in the range between (11000 ± 6600) 103kg/a and (16000 ± 9100) 103kg/a. These results, as well as the other estimates, suggest that the accretion rate of micrometeorites in the last glacial period was comparable to that in the present.
Key words: Micrometeorite, accretion rate, Antarctica, last glacial periods, noble gas, interplanetary dust particle.