Keiichi Sasaki - Academia.edu (original) (raw)

Papers by Keiichi Sasaki

Eos, Transactions American Geophysical Union, 2006

Annual Meeting of the Geological Society of Japan, 2010

Annual Meeting of the Geological Society of Japan The 120th Annual Meeting(2013' Sendai), 2013

Geochimica et Cosmochimica Acta, Oct 1, 2017

Japan Geoscience Union, May 1, 2015

Journal of Coastal Research, 2019

ABSTRACT Bassi, D.; Iryu, Y.; Humblet, M.; Matsuda, H.; Machiyama, H.; Sasaki, K.; Matsuda, S.; A... more ABSTRACT Bassi, D.; Iryu, Y.; Humblet, M.; Matsuda, H.; Machiyama, H.; Sasaki, K.; Matsuda, S.; Arai, K., and Inoue, T., 2019. Deep-water macroid beds of the Ryukyu Islands, Japan: Encrusting acervulinids as ecosystem engineers. Journal of Coastal Research, 35(2), 463–466. Coconut Creek (Florida), ISSN 0749-0208. Encrusting acervulinid foraminifera can produce centimeter-sized, free-living coated grains named macroids. Macroid beds are an interesting feature of subtidal environments and have been recognized as important carbonate producers, habitat-forming structures, and paleoenvironmental indicators. Macroids provide a hard, three-dimensional substrate serving as microhabitat for a wide range of diverse organisms. As yet, the most extensive known occurrence of macroid beds in the western Pacific Ocean is found on the insular shelf of Kikai-jima, a coral reef–related island in the central Ryukyu Islands. The surveyed beds occur at water depth of 61–105 m arrayed on a ca. 6-km2 area. Despite their importance for the benthic communities of the Ryukyu Islands, only in the last decade have sampling efforts led to a more comprehensive understanding of the beds' distribution, their structure and associated communities, and the data concerning the influence of environmental factors on macroid beds and their ecological dynamics. In this study, the available information on the biodiversity associated with the recently described Ryukyu macroid beds are reviewed. This review is intended to inform and influence future research and policy planning on this largely unexplored, highly diverse marine ecosystem.

Journal of Geophysical Research: Oceans, 2016

The input history of 236U to the surface water of the Japan Sea was reconstructed through measure... more The input history of 236U to the surface water of the Japan Sea was reconstructed through measurement of the 236U/238U atom ratio in annual bands of a coral skeleton which was collected at Iki Island in the Tsushima Strait, the main entrance to the Japan Sea. The 236U/238U atom ratios and concentrations of U isotopes were measured for the period 1935–2010 using AMS and ICP‐MS. The 236U/238U atom ratios revealed three prominent peaks: 4.51 × 10−9 in 1955, 6.15 × 10−9 in 1959 and 4.14 × 10−9 in 1963; thereafter the isotope ratios gradually decreased over the next several decades, attaining a value of ca.1.3 × 10−9 for the present day. A simplified depth profile model for 236U in the Japan Sea, using the reconstructed 236U value for the surface water together with observed depth profiles for 236U in the water column in 2010, yielded diffusion coefficients of 3.4–5.6 cm2/s for 6 sampling points. The diffusion coefficient values obtained for the northern stations were relatively large, a...

IODP Scientific Prospectus, 2005

Earth and Planetary Science Letters, 1996

Marine Environmental Research, 2018

Quaternary International, 2004

Island Arc, 2006

High-resolution seismic reflection profiles delineated the distribution of mound-shaped reflectio... more High-resolution seismic reflection profiles delineated the distribution of mound-shaped reflections, which were interpreted as reefs, beneath the insular shelf western off Irabu Island, Ryukyus, southwestern Japan. A sediment core through one of the mounded ...

年報金沢大学環日本海域環境研究センター K Inet Kanazawa University, Mar 31, 2011

The Quaternary Research (Daiyonki-Kenkyu), 1998