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Journal Articles

Sediment trap record of alkenones from the East Sea (Japan Sea)

Lee, K. E.*; Khim, B.-K.*; Otosaka, Shigeyoshi; Noriki, Shinichiro*

Organic Geochemistry, 42(3), p.255 - 261, 2011/03

 Times Cited Count:14 Percentile:51.91(Geochemistry & Geophysics)

Long chain (C$$_{37}$$) alkenones in sinking particles obtained from the northeastern and the southern regions of the Japan Sea were examined to investigate the characteristics of production, export, and degradation of organic materials in the water column. A comparison of alkenone temperatures with satellite sea surface temperatures (SST) revealed that the alkenone temperatures were higher (6-13 $$^{circ}$$C) than SST during winter time, and lower (2-5 $$^{circ}$$C) during summer time. It indicated that there was a time lag between the SST and the trap records (about 3 months in winter and 1 month in summer). But, the annual average alkenone temperatures are close to annual average SST in the Yamato Basin. The reasons for this time lag can be (1) subsurface production of alkenones in summer and (2) slow settling velocity and long residence time of alkenones in the upper water column especially during winter time.

Journal Articles

Diagenesis and distribution of sterenes in Late Miocene to Pliocene marine siliceous rocks from Horonobe (Hokkaido, Japan)

Amo, Miki*; Suzuki, Noriyuki*; Shinoda, Toshio*; Ratnayake, N. P.*; Takahashi, Kazuharu

Organic Geochemistry, 38(7), p.1132 - 1145, 2007/07

 Times Cited Count:13 Percentile:60.83(Geochemistry & Geophysics)

Late Miocene to Pliocene marine siliceous rocks in Horonobe, Hokkaido, Japan are rich in sterenes and steradienes. Diagenetic degradation and transformation of sterenes and steradienes in immature Horonobe marine siliceous rocks of Wakkanai and Koetoi Formations were studied using the borehole core samples from HDB-3 and HDB-4 drilled by Japan Atomic Energy Agency. The paleo-temperatures of marine siliceous rocks were estimated to be in the range from 30 to 60 $$^{circ}$$C considering the silica mineral transformation from Opal-A to Opal-CT during diagenesis and the present day geothermal gradient in Horonobe region. Concentrations of steradienes and sterenes decrease quickly in the temperature range from 45 to 60 $$^{circ}$$C. The significant increase of sterane concentration in the same temperature range shows that a part of steranes is derived from sterenes and steradienes. The sterane/sterene ratios of C$$_{27}$$, C$$_{28}$$, and C$$_{29}$$ compounds change similarly with increasing maturity. The sterane/sterene ratio of Horonobe marine siliceous rocks can be a useful indicator of paleo-temperature. Either sterenes or steranes, the relative abundance of C$$_{27}$$, C$$_{28}$$, and C$$_{29}$$ compounds is kept nearly similar all through the Horonobe boreholes, showing that their relative abundance is still applicable to the characterization of organic matter in immature sediments.

Journal Articles

The Transfer capability of long-lived chernobyl radionuclides from surface soil to river water in dissolved forms

Amano, Hikaru; Matsunaga, Takeshi; Nagao, Seiya; *; Watanabe, Miki*; Ueno, Takashi; Onuma, Yoshikazu*

Organic Geochemistry, 30, p.437 - 442, 1999/00

 Times Cited Count:26 Percentile:46.09(Geochemistry & Geophysics)

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