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90Sr,106Ru, natural strontium and major elements were studied in 12 samples of beach deposits from Togi, Fukuura and Shiga, and in 26 samples of shallow water sediments from sea off Fukuura, Noto Peninsula, Ishikawa Pref., Japan.The average contents of natural strontium and90Sr in the beach deposits were 488 ppm ranging from 247 to 1,550 ppm and 45±9 pCi kg–1-dry mud ranging from 18 to 72 pCi kg–1-dry mud, respectively. While the average contents of natural strontium,90Sr and106Ru in the sediments were 234 ppm ranging from 136 to 415 ppm, 22±6 pCi kg–1-dry sand ranging from 7 to 48 pCi kg–1-dry sand and 0.6 ±0.2 nCi kg–1-dry ranging from 0.3 to 1.2 nCi kg–1-dry, respectively.The average contents of each natural strontium and90Sr in the beach deposits were about two times higher than those in the shallow water sediments. But no obvious relation of natural strontium to90Sr was found in all the samples. The enrichment of90Sr and108Ru in the beach deposits or tthe sediments were as high as 150320 and of 2,0003,000 compared with average contents of90Sr and106Ru in a liter of surface water from the Japan Sea. It is to be noticed that the average106Ru to90Sr ratio of 27 for the shallow water sediments is much higher than the average of 1.0 for surface sea water of the Japan Sea.As to major elements of the samples, the beach deposits are rich in silicon (Av. 70.89 ±0.92% SiO2), but poor in iron (Av. 2.99±0.32% Fe2O3). Whereas the shallow water sediments are poor in silicon (Av. 52.96±10.33% SiO2) and rich in iron (Av. 5.50±1.90% Fe2O3), calcium (Av. 9.64±9.22% CaO) and magnesium (Av. 2.83±1.58% MgO). 相似文献
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R. Kondo S. Tsukamoto H. Tachibana Y. Miyairi Y. Yokoyama 《Quaternary Geochronology》2007,2(1-4):260-265
The timing of glacial advances, periglacial phenomena, and the ages of two marker tephras in northern Hokkaido were estimated by OSL dating. It appears that the glacier of Yamunai 2 stage on Rishiri Island expanded between 24 and 15 ka. In northern Hokkaido, OSL ages indicate ice wedge formation during the period 24–18 ka. These results indicate that both the glacial advance and the development of ice wedges were synchronous phenomena relating to the Last Glacial Maximum. 相似文献
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Aiko Tachibana Yuichiro Nishibe Hideki Fukuda Kyoko Kawanobe Atsushi Tsuda 《Journal of Oceanography》2017,73(1):55-65
The tsunami caused by the 2011 off the Pacific coast of Tohoku Earthquake seriously damaged the Pacific coast of northeastern Japan. In addition to its direct disturbance, a tsunami can indirectly affect coastal pelagic ecosystems via topographical and environmental changes. We investigated seasonal changes in the phytoplankton community structure in Otsuchi Bay, northeastern Japan, from May 2011, which was 2 months after the tsunami, to May 2013. The phytoplankton species composition in May 2011 was similar to that observed in May 2012 and 2013. The present results are consistent with the dominant species and water-mass indicator species of phytoplankton in past records. These results suggest that there was no serious effect of the tsunami on the phytoplankton community in Otsuchi Bay. Community analysis revealed that two distinct seasonal communities appeared in each year of the study period. The spring–summer community was characterized by warm-water Chaetoceros species, and dinoflagellates appeared from May to September. The fall–winter community was characterized by cold neritic diatoms, which appeared from November to March. The succession from the spring–summer community to the fall–winter community took place within a particular water mass, and the fall–winter community appeared in both the surface water and the Oyashio water mass, suggesting that water-mass exchange is not the only factor that determines the phytoplankton community structure in Otsuchi Bay. 相似文献