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Last Updated :2024/09/10

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Master

Affiliation (Master)

  • Faculty of Science　Earth and Planetary Sciences　Earth and Planetary System Science

Affiliation (Master)

  • Faculty of Science　Earth and Planetary Sciences　Earth and Planetary System Science

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Profile and Settings

Degree

  • 1998 Doctor of Science (Nagoya University)（Nagoya University）

Profile and Settings

  • Name (Japanese)

    Sawada

  • Name (Kana)

    Ken

  • Name

    200901017713917883

Alternate Names

Achievement

Research Interests

  • biogeochemistry   organic sedimentology   microalgae   kerogen   Resistant macromolecule   Molecular fossil   Paleoclimatology   biomarker   Paleoceanography   Organic Geochemistry   Geomacromolecule   Paleobiology   Paleovegetation   Paleothermometry   Sediment   Paleoecology   Paleoenvironment   

Research Areas

  • Natural sciences / Solid earth science
  • Natural sciences / Biogeoscience
  • Life sciences / Ecology and environmental science
  • Natural sciences / Space and planetary science

Research Experience

  • 2020 - Today Hokkaido University Department of Earth and Planetary Sciences, Faculty of Science Professor
  • 2015 - 2020 Hokkaido University Department of Earth and Planetary Sciences, Faculty of Science Associate Professor
  • 2013 - 2015 Hokkaido University Department of Natural History Sciences, Faculty of Science Associate Professor
  • 2006 - 2012 Hokkaido University Lecturer
  • 2001 - 2006 Hokkaido University Lecturer
  • 1997 - 2000 University of Tsukuba Department of Chemistry
  • 1997 - 2000 1997- Researcher,1997-2000 Research Associate, Department of Chemistry, University of Tsukuba.

Education

  • 1993 - 1997  Nagoya University  Graduate School of Science  Doctor Course
  •        - 1997  Nagoya University  Graduate School, Division of Natural Science
  •        - 1991  Shinshu University  Faculty of Science
  •        - 1991  Shinshu University  Faculty of Science

Awards

  • 2023/07 Communications Earth & Environment Outstanding Reviewer Award
     
    受賞者: Ken Sawada
  • 2021 日本有機地球化学会 2021年有機地球化学会賞（学術賞）
     
    受賞者: 沢田健

Published Papers

  • Reishi Takashima, D. Selby, T. Yamanaka, Y. Kuwahara, H. Nakamura, K. Sawada, M. A. Ikeda, T. Ando, K. Hayashi, M. Nishida, T. Usami, D. Kameyama, H. Nishi, A. Kuroyanagi, B. R. Gyawali
    Communications Earth & Environment 2662-4435 2024/02/19 [Refereed]
     
    AbstractDuring mid-Cretaceous Oceanic Anoxic Event 2, significant increase of atmospheric carbon dioxide concentrations from the eruption of the large igneous provinces is hypothesized to have induced a humid climate and an elevation in nutrient runoff from continents to the oceans, resulting in oxygen depletion in the ocean. However, hitherto there is limited insight into the driving factors of Oceanic Anoxic Event 2 from the Pacific and Asian continental margins, even though the former and the latter were the largest ocean and landmass at that time. Here, a multiproxy analysis for the Oceanic Anoxic Event 2 interval of the Yezo Group –deposited on northwestern Pacific along the active Asian continental margin– is interpretated to identify seven volcanic pulses, five of which may have elevated humidity, weathering intensity, and vegetational change in the eastern margin of Asia. Moreover, oxygen depletion occurred simultaneously in the northwest Pacific. Given that these environmental changes in the eastern margin of Asia were penecontemporaneous with the global carbon burial intervals during Oceanic Anoxic Event 2, the elevated nutrient supply from the Asian continental margin to the Pacific Ocean may have, in part, contributed to the worldwide depletion of oxygen of the ocean during Oceanic Anoxic Event 2.
  • Hiroyasu Asahi, Ken Sawada
    Organic Geochemistry 188 104671 - 104671 0146-6380 2024/02 [Refereed]
  • Gen Sakugawa, Masashi A. Ikeda, Takuto Ando, Reishi Takashima, Hiroshi Nishi, Ken Sawada
    GEOCHEMICAL JOURNAL 58 (4) 138 - 154 0016-7002 2024
  • 星 恒太郎, 小林 まどか, 桑田 晃, 沢田 健
    Researches in Organic Geochemistry 39 (2) 69 - 85 2023/12 [Refereed]
  • Muhammad Adam Ismail, Hiroyasu Asahi, Ken Sawada
    SEDIMENTARY GEOLOGY 454 0037-0738 2023/08 [Refereed]
     
    Extrabasinal turbidity currents, also known as hyperpycnal flows, can deposit vast amounts of organic carbon to the marine realm. On the other hand, intrabasinal turbidity currents are commonly thought to resuspend and fur-ther oxidize organic matter (OM), creating deposits with poor preservation of terrestrial OM. However, recent studies have shown that intrabasinal turbidity currents can still preserve terrigenous OM after reworking previ-ously deposited OM-rich sediments. As such, both types of turbidity currents may act as unconventional source rocks. Considering that there is a discrepancy between global carbon burial fluxes in the marine environment and the amount of organic carbon delivered by rivers, OM preservation within such sandy deposits should not be overlooked. We investigated both plant fragment-rich extrabasinal and intrabasinal turbidites of the Miocene Ka-wabata Formation (Hokkaido, Japan) by using biomarker distributions within different facies formed by changes in sediment concentration due to progressive deposition during waning flow. Clear distinctions in terms of sed-imentological features and organic geochemical characteristics between different facies were found and are interpreted to be caused by different OM sources and sedimentological processes. The sandy extrabasinal turbi-dites have high amounts of organic carbon, high pristane/phytane ratios, and fewer amounts of marine algal bio-markers due to direct transport from the terrestrial environment without mixing with marine waters. Intrabasinal, Bouma-type turbidites generally have poor OM, and low pristane/phytane values but high concen-trations of algal biomarkers since sediments are sourced from the marine environment. In both extrabasinal and intrabasinal turbidites of this study, the plant fragment-rich sandy layers deposited by flows with lower sediment concentrations preserve high amounts of terrigenous OM, possibly due to having densities allowing woody plant fragments to remain within the flow and corresponding deposit, while basal Ta sandstones and Te hemipelagic deposits contain more marine OM due to erosion plus incorporation of marine sediments and mixing with ma-rine waters respectively. Mud clasts formed in basal flows such as surge-like intrabasinal turbidity currents may also enhance OM preservation in plant fragment-poor sandstones. & COPY; 2023 Elsevier B.V. All rights reserved.
  • Ryosuke Fukuchi, Nozomi Hatano, Hiroyasu Asahi, Ken Sawada
    Researches in Organic Geochemistry 39 (1) 21 - 34 2023/07 [Refereed][Not invited]
  • Masashi A. Ikeda, Hideto Nakamura, Ken Sawada
    Organic Geochemistry 179 104588 - 104588 0146-6380 2023/05 [Refereed]
  • Shiho Kurosawa, Satoshi Furota, Mayu Mitsui, Ken Sawada, Koji Seike, Noboru Furukawa, Makoto Ito
    Sedimentology 2022/11/29 [Refereed]
  • Takuto Ando, Ken Sawada, Kazuki Okano, Reishi Takashima, Hiroshi Nishi
    Palaeogeography, Palaeoclimatology, Palaeoecology 586 110779 - 110779 0031-0182 2022/01 [Refereed]
  • Hara Yuki, Ando Takuto, Sawada Ken
    Researches in Organic Geochemistry 日本有機地球化学会 37 (2) 73 - 88 1344-9915 2021/12 [Refereed][Not invited]
     
    Branched aliphatic alkanes with quaternary substituted carbon atoms (BAQCs) were frequently identified in ancient sedimentary rocks, and modern sediments and deep sea waters. The BAQCs are considered to be originated from by bacteria and microalgae, but also to be formed by anthropogenic petroleum products as contamination of geological samples. In the present study, we analyzed the BAQCs in sedimentary rocks of the Mesoproterozoic Qaanaaq Formation in Greenland by GC-MS. We identified various BAQCs as aliphatic hydrocarbons. Moreover, we examined the sources of BAQCs, which are originated from the ancient microbial ecosystems or contamination from anthropogenic petroleum products.
  • Masashi A. Ikeda, Hideto Nakamura, Ken Sawada
    Phytochemistry 189 112823 - 112823 0031-9422 2021/06 [Refereed][Not invited]
     
    The hydrocarbons of eight lichen species isolated in Japan were analyzed, and diverse mono-, di-, and triunsaturated alkenes were detected. The positions of the double bonds of C17 alkadienes (heptadecadiene) and C17-C20 alkenes were determined by mass spectrometry of their dimethyl disulfide adducts. We found that the six lichens containing green algal photobionts were distinguished by the presence of 1,8-heptadecadiene, 6,9-heptadecadiene, and 8- and 7-heptadecenes. On the other hand, 1-octadecene, 4-octadecene, and 5-nonadecene were the major alkene components of the two lichens with cyanobacterial photobionts. These alkadienes and alkenes were present in large quantities in the lichen samples. In particular, 1,8-heptadecadiene accounted for more than 90% of the total alkenes in all four lichens containing it. Our results provide new insights into the origin of C17 alkadienes and C17-C20 alkenes in environmental and geological samples, and these alkenes can potentially be applied as lichen biomarkers.
  • Satoshi Furota, Ken Sawada, Gentaro Kawakami
    INTERNATIONAL JOURNAL OF COAL GEOLOGY 233 0166-5162 2021/01 [Refereed]
     
    Occasionally, distinctive plant fragment (PF)-concentrated sandstone beds are found in the turbiditic sequence of the Miocene Kawabata Formation (Yubari, central Hokkaido, Japan) deposited in a foredeep basin. Sedimentological and organic geochemical analyses were carried out on the PF-concentrated sandstone bed to investigate the transport and depositional processes of the abundant PFs in the basin. The PF-concentrated sandstone bed was subdivided into lower and upper PF-concentrated layers based on their sedimentary structures. The lower layer contains chaotically dispersed PFs, and the upper layer is characterized by PF laminae. The dispersed PFs in the lower layer were likely deposited by rapid depositional processes such as freezing or rapid fall-out of suspended particles. The huge amount of PF deposition was confirmed by biomarker data such as sterane distributions and pristane/phytane ratios. The compositions of n-alkanes and diterpenoids in the PF-concentrated sandstone bed are distinct from those in the other sandstone and mudstone beds. These results imply that the terrigenous particles originated from specific terrestrial higher plants that were effectively transported and deposited, resulting in formation of the PF-concentrated sandstone bed. The distinctive sedimentary structures observed in the sequences could be attributed to a large flood discharge and the huge volume of PFs might have been transported directly from an upper reach of river and then reached the deep-sea basin by density flows, such as relatively concentrated hyperpycnal flows.
  • Kotaro Toyama, Adina Paytan, Ken Sawada, Takashi Hasegawa
    Chemical Geology 535 119454 - 119454 0009-2541 2020/03 [Refereed][Not invited]
  • Ken Sawada, Makiko Ono, Hideto Nakamura, Shafi Mohammad Tareq
    Quaternary International 2020/03 [Refereed][Not invited]
  • GC/MS analyses of ring degraded triterpenoids in event deposits
    Hiroyasu Asahi, Ken Sawada
    Researches in Organic Geochemistry 35 55 - 72 2019/12 [Refereed][Not invited]
  • Minoru Tsukagoshi, Ken Sawada, Shin‐ichi Akimoto
    Entomological Science 22 (3) 270 - 274 1343-8786 2019/09 [Refereed][Not invited]
  • Reishi Takashima, Hiroshi Nishi, Toshiro Yamanaka, Yuji Orihashi, Yasuyuki Tsujino, Xavier Quidelleur, Keiichi Hayashi, Ken Sawada, Hideto Nakamura, Takuto Ando
    Newsletters on Stratigraphy 52 (3) 341 - 376 0078-0421 2019/06 [Refereed][Not invited]
     
    © 2019 Gebrüder Borntraeger, Stuttgart, Germany. The Yezo Group, exposed in Hokkaido, northern Japan, is one of the few strata that recorded Cretaceous paleo-oceanographic changes in the Pacific Ocean. Although the group yields abundant marine macro- and microfossils, sporadic occurrences of age-diagnostic species in several stratigraphic intervals has prevented high-resolution international biostratigraphic correlation. The proposed integrated bio- and carbon isotope stratigraphy of the Yezo Group, which is exposed in northwest Hokkaido, enables high-resolution international stratigraphic correlation spanning from Upper Albian to Lower Campanian. The correlation of the present study identifies the detailed stratigraphic horizons of the Albian/Cenomanian, Cenomanian/ Turonian, Turonian/Coniacian, Coniacian/Santonian, and Santonian/Campanian boundaries, as well as the Late Cretaceous paleo-environmental events in the Yezo Group. The Yezo Group is also important in order to complement the chronometric age of the Cretaceous geologic time scale because the group includes numerous felsic tuffs. The U-Pb zircon ages of some of these tuffs, which are interbedded near the Albian/Cenomanian, Coniacian/Santonian and the Santonian/Campanian boundaries in the Yezo Group, are dated at 99.7±0.3 Ma (Quidelleur et al. 2011), 86.87±0.60/0.67 (internal/total error) Ma and 84.7±0.7/1.8 (internal/total error) Ma, respectively. These radiometric ages are consistent with the latest age model of the Cretaceous time scale.
  • Satoshi Furota, Hideto Nakamura, Ken Sawada
    29th International Meeting on Organic Geochemistry, IMOG 2019 2019
  • Fahmida Parvin, Osamu Seki, Koji Fujita, Yoshinori Iizuka, Sumito Matoba, Takuto Ando, Ken Sawada
    Atmospheric Environment 196 86 - 94 1352-2310 2019/01 [Refereed][Not invited]
     
    © 2018 The Authors We provide continuous records of biomass burning molecular tracers (levoglucosan and dehydroabietic acid) in a Greenland ice core collected from the Southeastern Dome (the SE-Dome ice core) over the past several decades to assess the paleoclimatic utility of these tracers in Greenland ice cores. An air mass backward-trajectory analysis indicates that eastern Canada is likely the primary source region of the biomass burning tracers. Comparisons of levoglucosan and dehydroabietic acid data in the SE-Dome ice core and area burned (vegetation fire) events in Canada suggests that the biomass burning tracers in the ice core document most of the pronounced biomass burning events in eastern Canada over the past several decades, confirming that analyses of biomass burning molecular tracers in Greenland ice cores are useful to reconstruct the frequency of significant biomass burning events in a local region. However, our study also highlights that the wind pattern when the biomass burning occurs is decisive for the registration of a biomass burning event in an ice core even though long-term changes in the wind regime associated with decadal-scale climate oscillations do not significantly influence the transport and deposition of biomass burning tracers on the Greenland ice sheet.
  • Eri Kitamura, Tomonori Kotajima, Ken Sawada, Iwane Suzuki, Yoshihiro Shiraiwa
    Scientific Reports 8 (1) 2196  2045-2322 2018/12/01 [Refereed][Not invited]
     
    The cosmopolitan marine haptophyte alga Emiliania huxleyi accumulates very long-chain (C37-C40) alkyl ketones with two to four trans-type carbon-carbon double bonds (alkenones). These compounds are used as biomarkers of haptophytes and as palaeothermometers for estimating sea-surface temperatures in biogeochemistry. However, the biosynthetic pathway of alkenones in algal cells remains enigmatic, although it is well known that the C37 tri-unsaturated alkenone (K37:3) becomes dominant at low temperatures, either by desaturation of K37:2 or by a separate pathway involving the elongation of tri-unsaturated alkenone precursors. Here, we present experimental evidence regarding K37:3 synthesis. Using the well-known cosmopolitan alkenone producer E. huxleyi, we labelled K37:2 with 13C by incubating cells with 13C-bicarbonate in the light at 25 °C under conditions of little if any K37:3 production. After stabilisation of the 13C-K37:2 level by depleting 13C-bicarbonate from the medium, the temperature was suddenly reduced to 15 °C. The 13C-K37:2 level rapidly decreased, and the 13C-K37:3 level increased, whereas the total 13C-K37 level-namely [K37:2 + K37:3]-remained constant. These 13C-pulse-chase-like experimental results indicate that 13C-K37:2 is converted directly to 13C-K37:3 by a desaturation reaction that is promoted by a cold signal. This clear-cut experimental evidence is indicative of the existence of a cold-signal-triggered desaturation reaction in alkenone biosynthesis.
  • Masashi A. Ikeda, Hideto Nakamura, Ken Sawada
    Researches in Organic Geochemistry 日本有機地球化学会 34 (2) 15 - 28 1344-9915 2018/12 [Refereed][Not invited]
     
    Aliphatic hydrocarbons were analyzed in 3 species (Cladonia vulcani, Cladonia scabriuscula, and Xanthoria sp.) of lichens collected from Hokkaido and Hyogo Prefectures, Japan. Molecular composition of n-alkanes is likely influenced by precipitation, as the long chain n-alkanes are produced under arid environments. Alkenes such as heptadecene are also detected as major components in these samples. Molecular composition of these alkanes is different between the genus Xanthoria and Cladonia, suggesting that the composition is influenced by taxonomic diversity. Molecular composition of the aliphatic hydrocarbons other than n-alkanes and alkenes detected are far different between the genera Xanthoria and Cladonia, but are almost similar in these 2 species of the genus Cladonia, potentially depending on taxonomy at the genus level. From these results, we predict that the alkenes, as well as other aliphatic hydrocarbons, can be useful as a chemotaxonomic marker, while the composition of n-alkanes can be an environmental indicator.
  • Ken Sawada, Takaaki Arai, Hideto Nakamura, Minoru Tsukagoshi
    Researches in Organic Geochemistry 34 37 - 45 2018/12 [Refereed][Not invited]
  • Hiroya Araie, Hideto Nakamura, Jaime L. Toney, Heather A. Haig, Julien Plancq, Takashi Shiratori, Peter R. Leavitt, Osamu Seki, Ken-ichiro Ishida, Ken Sawada, Iwane Suzuki, Yoshihiro Shiraiwa
    Organic Geochemistry 121 89 - 103 0146-6380 2018/07/01 [Refereed][Not invited]
     
    Alkenone-producing species have been recently found in diverse lacustrine environments, albeit with taxonomic information derived indirectly from environmental genomic techniques. In this study, we isolated alkenone-producing algal species from Canadian saline lakes and established unialgal cultures of individual strains to identify their taxonomical and molecular biological characteristics. Water and sediments collected from the lakes were first enriched in artificial seawater medium over a range of salinities (5–40 g/L) to cultivate taxa in vitro. Unialgal cultures of seven haptophyte strains were isolated and categorized in the Isochrysis clade using SSU and LSU rRNA gene analysis. The alkenone distributions within isolated strains were determined to be novel compared with other previously reported alkenone-producing haptophytes. While all strains produced the typical C37 and C38 range of isomers, one strain isolated from Canadian salt lakes also produced novel C41 and C42 alkenones that are temperature sensitive. In addition, we showed that all alkenone unsaturation indices (e.g., U37 K and U37 K′) are temperature-dependent in culture experiments, and that alkenoate indices (e.g., U37 A, U38 A, RIA38 and A37/A38) provide alternative options for temperature calibration based on these new lacustrine algal strains. Importantly, these indices show temperature dependence in culture experiments at temperatures below 10 °C, where traditional alkenone proxies were not as sensitive. We hypothesize that this suite of calibrations may be used for reconstructions of past water temperature in a broad range of lakes in the Canadian prairies.
  • Yaeko Igarashi, Tomohisa Irino, Ken Sawada, Lu Song, Satoshi Furota
    Global and Planetary Change 163 1 - 9 0921-8181 2018/04/01 [Refereed][Not invited]
     
    We reconstructed fluctuations in the East Asian monsoon and vegetation in the Japan Sea region since the middle Pliocene based on pollen data obtained from sediments collected by the Integrated Ocean Drilling Program off the southwestern coast of northern Japan. Taxodiaceae conifers Metasequoia and Cryptomeria and Sciadopityacere conifer Sciadopitys are excellent indicators of a humid climate during the monsoon. The pollen temperature index (Tp) can be used as a proxy for relative air temperature. Based on changes in vegetation and reconstructed climate over a period of 4.3 Ma, we classified the sediment sequence into six pollen zones. From 4.3 to 3.8 Ma (Zone 1), the climate fluctuated between cool/moist and warm/moist climatic conditions. Vegetation changed between warm temperate mixed forest and cool temperate conifer forest. The Neogene type tree Carya recovered under a warm/moist climate. The period from 3.8 to 2.5 Ma (Zone 2) was characterized by increased Metasequoia pollen concentration. Warm temperate mixed forest vegetation developed under a cool/moist climate. The period from 2.5 to 2.2 Ma (Zone 3) was characterized by an abrupt increase in Metasequoia and/or Cryptomeria pollen and a decrease in warm broadleaf tree pollen, indicating a cool/humid climate. The Zone 4 period (2.2–1.7 Ma) was characterized by a decrease in Metasequoia and/or Cryptomeria pollen and an increase in cool temperate conifer Picea and Tsuga pollen, indicating a cool/moist climate. The period from 1.7 to 0.3 Ma (Zone 5) was characterized by orbital-scale climate fluctuations. Cycles of abrupt increases and decreases in Cryptomeria and Picea pollen and in Tp values indicated changes between warm/humid and cold/dry climates. The alpine fern Selaginella selaginoides appeared as of 1.6 Ma. Vegetation alternated among warm mixed, cool mixed, and cool temperate conifer forests. Zone 6 (0.3 Ma to present) was characterized by a decrease in Cryptomeria pollen. The warm temperate broadleaf forest and cool temperate conifer forest developed alternately under warm/moist and cold/dry climate. Zone 2 corresponded to a weak Tsushima Current breaking through the Tsushima Strait, and the beginning of orbital-scale climatic changes at 1.7 Ma during Zone 5 corresponded to the strong inflow of the Tsushima Current into the Japan Sea during interglacial periods (Gallagher et al., 2015).
  • GC/MS analyses of phenolic diterpenoids in sediment and Cryptomeria leaf
    AOYAGI Chiaki, SAWADA Ken
    Researches in Organic Geochemistry 33 17 - 27 2017/12 [Refereed][Not invited]
  • Takuto Ando, Ken Sawada, Kazuki Okano, Reishi Takashima, Hiroshi Nishi
    ORGANIC GEOCHEMISTRY 106 13 - 24 0146-6380 2017/04 [Refereed][Not invited]
     
    Desmethyl and A-ring methyl triaromatic (TA) steroids, including dinosteroids, were analyzed in the sediments deposited during the mid-Cretaceous oceanic anoxic events (OAEs) 1a (Goguel), 1b (Jacob, Kilian and Paquier) and 1d (Breistroffer) from the Vocontian Basin, SE France. These TA steroids were identified by GC-MS using non-polar (DB5-HT) and mid-polar (VF-200 ms) columns; their peaks are more clearly separated by the mid-polar column. The triaromatic dinosteroid indices (TADS and TADS') are defined as alternative indicators for reconstructing dinoflagellate production. In these relationships, the TADS' values tend to increase in the samples that have higher abundances of the co-eluted 3-methyl TA steroids. The TADS values are lower in the Goguel, Jacob and Kilian samples but increase in the Paquier and Breistroffer samples, and are especially consistently higher in the Paquier. These results suggest that dinoflagellates flourished under the stratified and eutrophic conditions in surface waters during the Paquier deposition (OAE1b). Moreover, an inverse correlation between the TADS and C-27 TA steroid (TAS) values is noticeable in the samples from the Kilian and Paquier deposits. Thus, the C-27 TA steroids in these sediments, which originated from C-28 sterols, may be primarily derived from an ecological competitor of dinoflagellates. We propose that their competitors are possibly coccolithophorids and/or prasinophyte algae. During the mid-Cretaceous hothouse period, coccolithophorids/prasinophytes had the potential to flourish under more oligotrophic conditions, whereas dinoflagellates were dominant as primary producers under eutrophic conditions. (C) 2017 Elsevier Ltd. All rights reserved.
  • Ando Takuto, Sawada Ken
    Researches in Organic Geochemistry 日本有機地球化学会 33 (1) 29 - 35 1344-9915 2017 [Refereed][Not invited]
  • Takuto Ando, Ken Sawada, Hideto Nakamura, Keita Omatsu, Reishi Takashima, Hiroshi Nishi
    ISLAND ARC 26 (1) e12178  1038-4871 2017/01 [Refereed][Not invited]
     
    Biomarker analyses for evaluating maturity of organic matter and depositional environments such as redox conditions, were performed in sediments across the Cenomanian-Turonian boundary (CTB) in the Saku Formation of the Yezo Group distributed along the Shumarinai-gawa River and the Omagari-zawa River, both in the Tomamae area, Hokkaido, Japan. Maturity indicators using steranes and hopanes, show that organic matter in sediments from the Shumarinai-gawa and Omagari-zawa sections are of lower maturity than those from the Hakkin-gawa section (Oyubari area). Moreover, the beta beta hopane ratios clearly show that the maturity of the Shumarinai-gawa samples is lower than that of the Omagarizawa samples. These variations in the maturity of organic matter presumably reflect the difference in their burial histories. The results for the pristane/phytane (Pr/Ph) ratios suggest that the Shumarinai-gawa samples were deposited under dysoxic to anoxic environments across the CTB, while the depositional environments of the Omagari-zawa samples were relatively oxic. By another paleoredox indicator using C-35 homohopanoids including a homohopene index (HHenI), higher values are observed in the Shumarinai-gawa section, particularly in the horizons of the preceding period and an early stage of the first negative shift phase and the latest oceanic anoxic event 2 (OAE2) interval. These results suggest that the Shumarinai-gawa samples record dysoxic to anoxic environments across the CTB. In contrast, the signals for the C35 homohopanoid index values show a relatively oxic condition in the Omagari-zawa section. The trends of stratigraphic variations in redox conditions are different from those in the OAE2 interval in the proto-Atlantic and Tethys regions as reported previously. Hence, the redox variations in the Tomamae area were basically related to a local environmental setting rather than global anoxia. However, the prominent anoxic emphasis observed in the HHenI profile of the Shumarinai-gawa section can be a distinctive, and possibly global, event in the North-West Pacific just before the OAE2.
  • Satoshi Furota, Hideto Nakamura, Ken Sawada
    ORGANIC GEOCHEMISTRY 101 166 - 175 0146-6380 2016/11 [Refereed][Not invited]
     
    Long-chain alkenones and related compounds were analyzed in Miocene and Pliocene sediments from the Gulf of Cadiz (GoC) in the eastern North Atlantic, which were obtained by Integrated Ocean Drilling Project (IODP) Expedition 339. Both GC and GC-MS analyses using non-and mid-polar columns were performed on the sediments. Isomeric cis-C-37 alkenones were identified along with common trans-C-37-C-39 alkenones. The use of a mid-polar column resulted in the complete separation of the trans-C-37 triunsaturated alkenone and the cis-C-37 di-unsaturated alkenone and thus contributed to a more precise estimation of the alkenone-based paleotemperature. The reconstructed SSTs range from 26 to 28 degrees C during ca. 6-3 Ma in the GoC. These variations are concordant with global climate change during the period, particularly the Pliocene Climatic Optimum and the onset of sustained ice sheet growth in the northern hemisphere. The concentrations of C-37-C-39 alkenones and the C-37/C-38 alkenone ratios are lower during the late Miocene to early Pliocene and increase after ca. 4.2 Ma, which corresponds to the taxonomic change of the plausible alkenone producers from the genus Reticulofenestra to genera Gephyrocapsa and Reticulofenestra. Moreover, a C-38 di-unsaturated alkene-2,36-dione was tentatively identified. Variations in the concentrations of a tentatively identified alkenedione are almost synchronous with those of other alkenones, and their relative abundances decrease after ca. 4.2 Ma. These results suggest that the alkenedione originated from the ancient alkenone producers such as the genus Reticulofenestra. (C) 2016 Elsevier Ltd. All rights reserved.
  • Hideto Nakamura, Ken Sawada, Hiroya Araie, Takashi Shiratori, Ken-ichiro Ishida, Iwane Suzuki, Yoshihiro Shiraiwa
    ORGANIC GEOCHEMISTRY 99 78 - 89 0146-6380 2016/09 [Refereed][Not invited]
     
    We investigated the compositions of long chain alkenones and alkenoates in cultured strains of the marine haptophyte Tisochrysis lutea CCMP463 and T. lutea NIES-2590 (formerly classified as Isochrysis galbana). Both T. lutea strains grown at various temperatures of 15-35 degrees C could be characterized by the lack of tetraunsaturated alkenones and alkenoates in comparison with strains in other genera Isochrysis and Ruttnera, which are classified in the same family Isochrysidaceae and order Isochrysidales that contain alkenone-producing haptophytes. We found that T. lutea has a distinct alkenone response to temperature, which is characterized by high U37 -temperature sensitivity at 15-30 degrees C and continuing sensitivity at warm-end temperatures over 30 degrees C, where the other species fail to adapt. Both strains showed similar trends in alkenone compositions and alkenone unsaturation index temperature calibrations. In addition, both strains CCMP463 and NIES-2590 showed notably close phylogenetic relationships, even those that were collected from remote regions of the Atlantic Ocean, namely the Caribbean Sea and English Channel, where their habitats, particularly the sea surface temperature, are notably different. Considering previous published datasets, three genera, Isochrysis, Ruttnera and Tisochrysis, showed very different trends in the alkenone unsaturation index-temperature calibration. These results suggest that the lack of tetraunsaturated alkenones, warm-water oriented growth and the high sensitivity to growth temperature serve as distinct chemotaxonomic characteristics of T. lutea in the Isochrysidaceae family. (C) 2016 Elsevier Ltd. All rights reserved.
  • Tateshita Yuki, Sawada Ken, Ando Takuto, Ikeda Masayuki
    Researches in Organic Geochemistry 日本有機地球化学会 32 (2) 55 - 66 1344-9915 2016 [Refereed][Not invited]
  • Hideto Nakamura, Ken Sawada, Hiroya Araie, Iwane Suzuki, Yoshihiro Shiraiwa
    PHYTOCHEMISTRY 111 107 - 113 0031-9422 2015/03 [Refereed][Not invited]
     
    The hydrocarbons in cultures of marine haptophytes Emiliania huxleyi NIES837 and Gephyrocapsa oceanica NIES1315 were analyzed, and nonacosadienes and hentriacontadienes were detected as the major compounds in both strains. C-29 and C-31 monoenes and di-, tri- and tetra-unsaturated C-33 alkenes were also detected as minor compounds but not C-37 and C-38 alkenes. The positions of the double bonds in the C-29 and C-31 alkenes were determined by mass spectrometry of their dimethyl disulfide (DMDS) adducts. Among the four C-29 alkenes identified, the most abundant isomer was 2,20-nonacosadiene, and the other three compounds were 1,20-nonacosadiene, 3,20-nonacosadiene and 9-nonacosene, respectively. Hitherto, 2,20-nonacosadiene and 3,20-nonacosadiene were unknown to be natural products. The double bond at the n-9 (omega 9) position in these C-29 alkenes is hypothesized to be derived from precursors of unsaturated fatty acids possessing an n-9 double bond, such as (9Z)-9-octadecenoic acid. Nonacosadienes have the potential for being used as distinct haptophyte biomarkers. (C) 2015 Elsevier Ltd. All rights reserved.
  • Shinya Yamamoto, Ken Sawada, Hideto Nakamura, Madoka Kobayashi, Kimitaka Kawamura
    ORGANIC GEOCHEMISTRY 76 62 - 71 0146-6380 2014/11 [Refereed][Not invited]
     
    The stable carbon isotope ratio (delta C-13) values of sedimentary long chain (>C-20) n-alkanoic acids from the equatorial Pacific (IODP Sites U1331-1338) were measured for historical reconstruction of C-4 plant contribution from South America over the last 40 Ma. The values for C-30 and C-32 acids ranged between -36.9 parts per thousand and -25.4 parts per thousand, suggesting that they likely originated from higher plant wax associated with C-3-dominated vegetation. The molecular distribution of alkanoic acids in the sediments showed a marked change across the Intertropical Convergence Zone (ITCZ), indicating a potential contribution from the Northern Hemisphere to the sediments located at >10 degrees N. In contrast, the abundances of n-alkanoic acids significantly decreased in the sediments at <10 degrees N. The results suggest that the ITCZ may have acted as an effective barrier for the atmospheric transport of terrigenous biomarkers from the Northern Hemisphere, and the records presumably reflect the plant wax signal from the northern part of South America. The latitudinal variation in the delta C-13 values suggest that the differences in the core locations possibly caused north-and southward shifts of ca. -1.0 parts per thousand/degrees N and ca. +0.5 parts per thousand/degrees S from the equator, respectively. The corrected delta C-13 values of C-30 and C-32 acids did not cross the C-3 end member threshold until 1.7 Ma, despite the onset of C-4 plants in central South America at ca. 7 Ma. This implies that vegetation in the low latitudes of South America was less affected by hydrological changes induced by the uplift of the Andes during the late Miocene. (C) 2014 Elsevier Ltd. All rights reserved.
  • Osamu Seki, James A. Bendle, Naomi Harada, Madoka Kobayashi, Ken Sawada, Heiko Moossen, Gordon N. Inglis, Seiya Nagao, Tatsuhiko Sakamoto
    PROGRESS IN OCEANOGRAPHY 126 254 - 266 0079-6611 2014/08 [Refereed][Not invited]
     
    We measured TEX86 indices in surface sediments and sediment cores from marginal seas and open ocean sites in the North Pacific to test the accuracy of TEX86 paleothermometry in the region. Application of the global core top TEX86L and TEX86H, calibrations in the Sea of Okhotsk and northern North Pacific sub-polar region results in over- and under-estimations of TEX86 derived SSTs in surface sediments in deep-ocean and coastal areas, respectively. Further challenges apparent in applying TEX86L and TEX86H in late Quaternary sediment cores from the Okhotsk Sea (MR06-04 PC7) and northwestern Pacific (MR00-K03 PC1) are unrealistically warm Holocene mean annual reconstructed temperatures (TEX86L) and excessively cold Glacial temperatures (TEX1,16), compared with other high-latitude records and climate models. Application of a calibration based on a sub-set of deep (<1000 m) core-top sites appears to improve temperature reconstructions in the Holocene, but still yields underestimation of SSTs (mean annual = -5 degrees C for TEX86H) in the Glacial period in the Okhotsk Sea core MR06-04 PC7. However, a regional comparison of Okhotsk Sea and sub-polar surface sediment TEX86L values with observational sea-water temperatures at different seasons and water depths reveals that an optimized positive correlation is obtained with summer sub-surface temperatures (August, 20 m depth). The unique hydrographic setting of the Okhotsk Sea region likely exerts a strong control on the ecology of GDGT producers (assumed to be primarily be marine Thaumarchaeota), resulting in highly season and depth specific export production and a distinct regional gradient in surface sediment TEX86 values. When our new regional TEX86L calibration is applied to the sediment cores, TEX86L, and alkenone U-37(K') temperature estimates overlap in the Holocene and TEX86L produces plausible LGM to Holocene temperature reconstructions. Our study provides a region specific calibration and confirms the importance of acquiring local calibration equations, to optimize TEX86 paleothermometry for specific regions and ocean basins. (C) 2014 Elsevier Ltd. All rights reserved.
  • Hideto Nakamura, Ken Sawada, Hiroya Araie, Iwane Suzuki, Yoshihiro Shiraiwa
    ORGANIC GEOCHEMISTRY 66 90 - 97 0146-6380 2014/01 [Refereed][Not invited]
     
    The compositions of long chain alkenes, alkenones and alkenoates in a cultured strain of the haptophyte Chrysotila lamellosa CCMP1307, isolated from a salt marsh, were investigated. The biomarker patterns were distinctive and showed a high proportion of tetraunsaturated alkenones and alkenoates, with a pronounced proportion of C-40 alkenones and a lack of C-38 methyl and C-39 ethyl alkenones. Linear regression of the alkenone unsaturation degree (UK37K) with growth temperature (T) was obtained over the range of possible CCMP1307 growth temperature values (4-20 degrees C): UK37K = 0.045 x T (degrees C) - 1.016, (n = 13, r(2) 0.96), while the UK37K ' values were weakly correlated with T: UK37K ' = 0.0035T (degrees C) + 0.0511 (n = 18, r(2) 0.70). The UK37K calibration exhibited a low y-intercept in comparison with that of a Chinese inland lake strain reported previously. The data show significant intraspecific variation in UK37K for C. lamellosa between strains from different geographic origins. C. lamellosa CCMP1307 reproduced typical UK37K values observed in C-37:4 rich lakes, especially at lower temperature (< 15 degrees C). In addition, we identified C-29:2, C-31:1, C-31:2 and C-31:3 alkenes, and found that the unsaturation degree of C-31 alkenes (U-31(en)), calculated with C-31: 1 and C-31:2 alkenes, might also be a useful index of growth temperature for the haptophyte C. lamellosa. (C) 2013 Elsevier Ltd. All rights reserved.
  • Satoshi Furota, Ken Sawada, Gentaro Kawakami
    Researches in Organic Geochemistry 日本有機地球化学会 30 (1) 9 - 21 1344-9915 2014 [Refereed][Not invited]
     
    Distinctive plant fragment-concentrated sandstones are found in a turbiditic sequence deposited under deep sea environment in the Miocene Kawabata Formation distributed along the Higashiyama-gawa River, Yubari, central Hokkaido, Japan. We observed microscopically the plant fragments and analyzed terrestrial higher plant biomarkers in the sediments to evaluate sedimentological and hydrodynamic behaviors of plant particles by gravity flow depositional processes. Biomarker compositions such as pristane/phytane and regular sterane ratios indicate a large contribution of terrestrial organic matter, especially woody fragments, in the sandstone layer. The relative abundances of terrestrial higher plant terpenoids (pentacyclic triterpenoids, des-A-triterpenoids and diterpenoids) are high in all parts of the sandstone layer, while long-chain n-alkane concentrations are remarkably higher only at the uppermost part. Also, leaf cuticle fragments are mainly found in the uppermost part. These results suggest that plant leaves are mainly deposited in the uppermost part of the sandstone layer. Thus, it is concluded that the variations in plant fragment types (tissues) deposited are thought to be resulted from various hydrodynamic behavior in gravity flow.
  • Ken Sawada, Hideto Nakamura, Takaaki Arai, Minoru Tsukagoshi
    INTERNATIONAL JOURNAL OF COAL GEOLOGY 107 78 - 89 0166-5162 2013/03 [Refereed][Not invited]
     
    We investigated terpenoid biomarkers in muds from lignite seams, clays from porcelain clay beds that slightly contain lignite, and from a conifer cone macrofossil from the Miocene Tokiguchi Porcelain Clay Formation of the Tokai Group in central Japan, as well as extant cones. The n-alkanes, n-alkanols (suberin origin), diterpenoids (conifer origin), hopanoids (bacteria origin) and steroids were mainly present in the lignite-containing muds and clays. On the other hand, the diterpenoids, triterpenoids (angiosperm origin), hopanoids and steroids were detected as major component in the conifer cone macrofossil. In addition, the diterpenoids were mainly detected in the extant conifer cones. The low hopane isomer ratios and the detection of biosterols are confirmed to be immature in the lignite, sediment and macrofossil in the formation. The stanol/sterol ratio values of the lignite-containing muds and clays are much higher than that of the macrofossil. The higher ratios in lignite-containing muds and clays are possibly attributed to enhanced microbial reduction of organic matter under reduced condition in the swampy environments. A large amount of angiosperm-derived triterpenoids detected in the conifer cone macrofossil are considered as contaminants in the sample from sedimentary organic particles originated from detrital waxes of angiosperms. Such contamination might occur by migration of organic compounds within sediment after deposition. The angiosperm-derived polar terpenoids may be hardly affected by contamination by migration of organic matter from the adjacent sediments because these are less abundant in the conifer macrofossil. Thus, it is suggested that the polar terpenoid biomarkers are more reliable as paleochemotaxonomic and paleovegetation indicators. (C) 2012 Elsevier B.V. All rights reserved.
  • Shuji Ogata, Yuma Miyata, Ken Sawada
    Researches in Organic Geochemistry 日本有機地球化学会 29 37 - 47 1344-9915 2013 [Refereed][Not invited]
     
    The type II kerogen from the Miocene Onnagawa Formation Shale was analyzed by pyrolysis and thermochemolysis with tetramethylammonium hydroxide (TMAH) and trimethylsulfonium hydroxide (TMSH) under various thermal conditions. The results were compared with that by alkali hydrolysis. The n-alkanes and n-alkenes in products by pyrolysis and thermochemolysis might be generated from alkyl moieties in geomacromolecule by thermal cracking of C-C bonds. The n-alkanoic acids (as fatty acid methyl esters; FAMEs) were mainly detected in the compounds released from the kerogen by thermochemolysis, indicating that they have been preserved through polymerization of marine plankton-derived compounds. Noticeably, the short chain () FAMEs were abundant in products by thermochemolysis, while those were hardly detected in hydrolysates. These short chain n-alkanoic acids might be mainly occluded in intra-aggregates within the geomacromolecule. In addition, the C_7 and C_9 FAMEs predominated in products by TMSH-using thermochemolysis, although the C_7 FAME was minor in TMAH method. It was suggested that the trapped and occluded compounds like C_7 and C_9 acids were more efficiently released from kerogen by TMSH thermochemolysis. On the other hand, total FAME/n-alkane ratios in the products by TMAH thermochemolysis were significantly higher than those by TMSH method. These results suggest that total recovery of the FAME released from kerogen by thermochemolysis can be lower in the presences of TMSH than TMAH.
  • Ken Sawada, Kunio Kaiho, Kazuki Okano
    JOURNAL OF ASIAN EARTH SCIENCES 54-55 78 - 90 1367-9120 2012/08 [Refereed][Not invited]
     
    Detailed fluorescent microscopic observations and organic geochemical analyses for insoluble sedimentary organic matter (kerogens) are conducted on the end-Permian to earliest Triassic sediments in the Meishan section A of South China. The main objectives of the present study are to reconstruct variations of marine and terrestrial environments, and to evaluate bulk characteristics of terrestrial input in the palaeo-Tethys ocean for the Permian-Triassic boundary (PTB). Most of kerogens in the Meishan section are mainly composed of marine algae-derived amorphous organic matter, while terrestrial plant-derived amorphous organic matter is remarkably dominant in the mass extinction horizon reported previously. The relative abundances of marine organic matter may vary depending on marine production rather than terrestrial input in the palaeo-Tethys associated with changing terrestrial vegetation. We also identified aromatic furans as major compounds in kerogen pyrolysate of all layers. It is possible that sources of aromatic furans with alkyl group, fungi and lichen, proliferated as disaster biota in terrestrial ecosystem through the PTB. Higher abundances of herbaceous organic matter are observed in the layers above the mass extinction horizon. However, the conifer biomarker retene can be identified in kerogen pyrolysates of all layers. These results imply that the productions of herbaceous plants increased as dominant pioneer biota in early stage of recovery for terrestrial ecosystem after its collapse, but also that woody plant potentially continued to be produced in land area throughout the end-Permian and earliest-Triassic. (C) 2012 Elsevier Ltd. All rights reserved.
  • Heiko Paelike, Mitchell W. Lyle, Hiroshi Nishi, Isabella Raffi, Andy Ridgwell, Kusali Gamage, Adam Klaus, Gary Acton, Louise Anderson, Jan Backman, Jack Baldauf, Catherine Beltran, Steven M. Bohaty, Paul Bown, William Busch, Jim E. T. Channell, Cecily O. J. Chun, Margaret Delaney, Pawan Dewangan, Tom Dunkley Jones, Kirsty M. Edgar, Helen Evans, Peter Fitch, Gavin L. Foster, Nikolaus Gussone, Hitoshi Hasegawa, Ed C. Hathorne, Hiroki Hayashi, Jens O. Herrle, Ann Holbourn, Steve Hovan, Kiseong Hyeong, Koichi Iijima, Takashi Ito, Shin-ichi Kamikuri, Katsunori Kimoto, Junichiro Kuroda, Lizette Leon-Rodriguez, Alberto Malinverno, Ted C. Moore, Brandon H. Murphy, Daniel P. Murphy, Hideto Nakamura, Kaoru Ogane, Christian Ohneiser, Carl Richter, Rebecca Robinson, Eelco J. Rohling, Oscar Romero, Ken Sawada, Howie Scher, Leah Schneider, Appy Sluijs, Hiroyuki Takata, Jun Tian, Akira Tsujimoto, Bridget S. Wade, Thomas Westerhold, Roy Wilkens, Trevor Williams, Paul A. Wilson, Yuhji Yamamoto, Shinya Yamamoto, Toshitsugu Yamazaki, Richard E. Zeebe
    NATURE 488 (7413) 609 - + 0028-0836 2012/08 [Refereed][Not invited]
     
    Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.
  • GC/MS analyses of A-ring methylsteroids (-sterane and -triaromatic sterane) in sedimentary rock
    Ando Takuto, SAWADA Ken
    Researches in Organic Geochemistry 28 31 - 41 2012 [Refereed][Not invited]
  • Makiko Ono, Ken Sawada, Yoshihiro Shiraiwa, Masako Kubota
    GEOCHEMICAL JOURNAL 46 (3) 235 - 247 0016-7002 2012 [Refereed][Not invited]
     
    A cultured strain of Isochrysis galbana UTEX LB 2307 was grown at 20 degrees C and 15 degrees C under salinity of 35 parts per thousand, 32 parts per thousand, 27 parts per thousand, 20 parts per thousand, and 15 parts per thousand, and analyzed for long chain (C-37-C-39) alkenones and (C-37-C-38) alkyl alkenoates. It was characterized by abundant C-37 alkenones and C-38 ethyl alkenoates (fatty acid ethyl ester: FAEEs) and a lack of C-38 methyl alkenones. There were no tetra-unsaturated (C-37:4) alkenones, which are frequently found in natural samples from low salinity waters. The alkenone unsaturation index (U-37(K')) did not vary in response to change in salinity at 15 degrees C. The alkenone unsaturation index (U-37(K')) clearly changed in response to change in salinity at 20 degrees C, but not at 15 degrees C, where algal growth was and was not limited by temperature at 15 degrees C and 20 degrees C, respectively. The U-37(K')-temperature calibration for I. galbana UTEX LB 2307 is quite different from those of E. huxleyi and another strain of I. galbana (CCMP1323), while is resemble to that reported for C. lamellosa isolated from a Chinese lake. Also, variation in the alkenone chain length ratio values (K-37/K-38) did not correlate with salinity. These results implied that a high abundance of tetra-unsaturated alkenone and high K-37/K-38 values might be attributed to a taxonomic factor rather than a physiological response to salinity change. Interestingly, our culture experiments showed that the ethyl alkenoates/alkenones ratio (EE/K-37) correlates with salinity. Hence, it is suggested that the EE/K-37 ratios are affected by the cellular and physiological factors against salinity condition in single haptophyte cells.
  • 骨化石中のコレステロールの炭素同位体組成を用いた海生哺乳類の古食性解析の研究
    新村龍也, 沢田健
    Researches in Organic Geochemistry 27 23 - 32 2011 [Refereed][Not invited]
  • Hideto Nakamura, Ken Sawada, Masamichi Takahashi
    ORGANIC GEOCHEMISTRY 41 (9) 975 - 980 0146-6380 2010/09 [Refereed][Not invited]
     
    The distributions of aliphatic and aromatic terpenoids in Cretaceous and Paleogene angiosperm fossils from Japan were investigated Aliphatic A ring-degraded oleanane, ursane and lupane were found in all samples In addition, aliphatic gymnosperm-derived diterpenoids were detected in significant quantities Aromatic oleanane-type triterpenoids were the major components, with ursane- and lupane-type triterpenoids being minor compounds in all angiosperm fossils. In a Cretaceous gymnosperm fossil, major components included aliphatic labdane-. isopimarane- and abietane-type diterpenoids, aromatic abietane-type diterpenoids, and chrysene- and picene-type polyaromatic hydrocarbons (PAHs) Trace amounts of oleanane-. ursane- and lupane-type triterpenoids were also identified It is likely that the aromatic triterpenoids were introduced to the gymnosperm fossil from the angiosperm-derived material in the sediments. We defined an angiosperm/gymnosperm index (al-AGI') as an alternative to the aliphatic triterpenoid/diterpenoid ratio proposed in the literature The al-AGI' index may underestimate the angiosperm contribution, because the aliphatic angiosperm-derived triterpenoids are more readily converted to aromatic counterparts than the ditemenoicls during diagenesis An aromatic angiosperm/gymnosperm index (ar-AGI) can be calculated using aromatic diterpenoids and triterpenoids We suggest that ar-AGI is best calculated using only the oleanane-, ursane- and lupane-type aromatic tnterpenoids, and that the chrysene- and picene-type PAHs be excluded (C) 2010 Elsevier Ltd All rights reserved.
  • Mitchell Lyle, Heiko Pälike, Hiroshi Nishi, Isabella Raffi, Kusali Gamage, Adam Klaus
    Scientific Drilling 9 (9) 4 - 15 1816-8957 2010/04 [Refereed][Not invited]
  • NAKAMURA Hideto, SAWADA Ken
    Chikyukagaku 一般社団法人日本地球化学会 44 (4) 205 - 219 0386-4073 2010 [Refereed][Not invited]
     
    Terrestrial higher plant terpenoids (HPTs) occurring in ancient marine and lacustrine sediments, are more refractory and constitute a more highly diversified family of molecules than the other terrestrial higher plant biomarkers including wax compounds and lignin phenols. Therefore, this HPT biomarker can be plant biogeochemical and paleontological indicators. Triterpenes such as oleanane are derived from various biological triterpenoids synthesized by almost all angiosperms. Diterpenenes such as retene are originated from abietane-type diterpenoids, which are constituents of gymnosperm, especially conifer. In pimarane and phyllocladane type diterpenoids, their precursors, source plants, and diagenetic products have been partly known. In addition, sesquiterpenoids are derived from both angiosperm and gymnosperm biosynthesized compounds. Several researchers have suggested that the HPT distributions were useful as the paleovegetation proxies for reconstructing the relative abundance of angiosperm to gymnosperm (e.g. angiosperm/gymnosperm index; AGI). Moreover, we recently examinated applicability of the indicator for angiosperm/gymnosperm ratio by using the HPTs in ancient plant fossils. In this paper, we review such HPT biomarkers and their applicability and reliability of the indicator as plant chemotaxonomy and paleovegetation in the ancient sediments.
  • SHINMURA Tatsuya, SAWADA Ken
    Chikyukagaku 日本地球化学会 44 (1) 17 - 29 0386-4073 2010 [Refereed][Not invited]
     
    Dietary preferences of archaeological and paleontological animals have been investigated based on stable carbon isotope ratios (δ13C) of collagen and non-collagenous proteins in fossil bones. The δ13C of individual compound in lipids from fossil bones were recently applied to the reconstruction of palaeodietary of animals. In the present study, we analyze the concentrations, class distributions, and δ13C values of fatty acids and steroids in the Pleistocene to Pliocene fossil whale and the Miocene fossil sea cow (Dusisiren sp.) bones, and evaluate their applicability as indicators of palaeodietary and fossil diagenesis. Biosynthetic steroids as cholesterol are detected in the Pleistocene whale bones, while the sterols are very poor in the older Pliocene whale samples, of which major steroids are their diagenetic compounds such as cholestanes and cholestenes. However, a large amount of cholesterol characterizes the Miocene fossil sea cow bone. We also can identify labile unsaturated fatty acids from all fossil whale and sea cow bones. It is suggested that the relative abundances of unsaturated to saturated fatty acids can be useful indicator for estimating diagenetic stage of fossil bones and checking contamination. The δ13C values of fatty acids in the fossil whale and sea cow bones range widely from -25.7 to -16‰, and there are differences of 1 to 4‰ between several fatty acid homologues within the same sample. Thus, the δ13C analyses of fatty acids in fossil bones may be less applicable for reconstructing palaeodietary. On the other hand, the δ13C values of steroidal compounds within the same sample are almost similar, although these values vary ranging between -29.6‰ and -24.4‰ among the different whale samples. Furthermore, the steroidal δ13C value in the sea cow sample is -20.5‰, which is concordant with that of food in sea cow. From these results, the δ13C value of steroid in fossil bone can be strongly useful tool for reconstructing palaeodietary of paleontological animal.
  • Change of the unsaturation degree of alkenones and alkenoates during acclimation to salinity change in Emiliania huxleyi and Gephyrocapsa oceanicawith reference to palaeosalinity indicator.
    Makiko Ono, Ken Sawada, Masako Kubota, Yoshihiro Shiraiwa
    Researches in Organic Geochemistry 25 53 - 60 2009 [Refereed][Not invited]
  • K. Kaiho, Z. Q. Chen, K. Sawada
    AUSTRALIAN JOURNAL OF EARTH SCIENCES 56 (6) 799 - 808 0812-0099 2009 [Refereed][Not invited]
     
    A 2-4 parts per thousand negative shift of 13C has been reported from many Permian/Triassic (P/Tr) boundary sections around the world. Our carbon isotopic measurements of bulk carbonate and organic matter from the Meishan section, South China show that a -3 parts per thousand shift of 13C spanned 30 ka over the end-Permian mass extinction. Carbon isotopic excursions (13Ccarb, 13Corg) coupled with 13C (=13Ccarb-13Corg), marine kerogen %, 87Sr/86Sr of siliciclastics and total organic carbon show geochemical signals underwent six geochemical variation zones (GVZ) over the P/Tr transition. Of these, GVZ 1 corresponds to the lower-middle parts of Bed 24e-1, GVZ 2 to the upper part of Bed 24e-1, GVZ 3 to Beds 24e-2, 24e-3, 25-2 and 25-2, GVZ 4 to Bed 25-3, GVZ 5 to Bed 26, and GVZ 6 to Beds 27-29. A -1 parts per thousand shift of 13C within 13 ka before the main extinction was probably generated by possible dissociation of methane hydrate by warming. Subsequent mixing of anoxic stratified ocean led to another-1 parts per thousand shift of 13C within 5 ka during the extinction. The-1 parts per thousand shift of 13C within 13 ka after the main extinction has probably resulted from massive denudation of soil and sediments caused by the collapse of forests and possible dissociation of methane hydrate at the end of the Permian. Furthermore, a dramatic drop of 13C values from 29-30 parts per thousand in Bed 24e-3 to 25 parts per thousand in Bed 25 indicates an abrupt proliferation of phototrophic sulfur bacteria immediately after the main episode of the end-Permian mass extinction. The 13C value increases to 29-30 parts per thousand in Bed 26 again, and this is probably due to massive denudation of soil and sediment caused by the collapse of forests between 0 and 27 ka after the main extinction, as revealed by negative shift of 13C. Low 13C value recorded in Beds 27-29 indicates that phototrophic sulfur bacteria may have thrived again and lasted more than 150 ka after the main extinction in the low-latitude Paleo-Tethys.
  • Ken Sawada, Takaaki Arai, Minoru Tsukagoshi
    ORGANIC GEOCHEMISTRY 39 (8) 919 - 923 0146-6380 2008/08 [Refereed][Not invited]
     
    We investigated the products released by hydrolysis of the resistant macromolecules of fossil dry fruits of angiosperms (Liquidambar and Nyssa) from the Pliocene fluvial sediments of the Tokai Group (central Japan), as well as extant dry fruits of Liquidambar, with respect to examining the chemotaxonomic potential and diagenetic alteration of these macromolecules. The main compounds released were n-alkanols, alpha,omega-alkanediols, alkanoic acids, omega-hydroxy acids and alpha,omega-alkanedioic acids. The carbon number distributions of the n-alkanols, alpha,omega-alkanediols and alkanoic acids released are similar for the fossil and extant dry fruits; the n-alkanols, presumably derived from suberin, are well preserved in the plant fossils. in contrast, the carbon number distributions of the w-hydroxy acids and alpha,omega-alkanedioic acids are different, suggesting diagenetic alteration. Similarly, high abundances of low molecular weight n-alkanols from fossil Nyssa suggest diagenetic incorporation of bacterial lipids into the geomacromolecule. (c) 2008 Elsevier Ltd. All rights reserved.
  • Kazuki Okano, Ken Sawada, Reishi Takashima, Hiroshi Nishi, Hisatake Okada
    ORGANIC GEOCHEMISTRY 39 (8) 1088 - 1091 0146-6380 2008/08 [Refereed][Not invited]
     
    Biomarker and total organic carbon (TOC) analyses were carried out on laminated black shales and massive marls from the Goguel level (OAE1a) and the Paquier and Kilian levels (OAE1b) of the Vocontian Basin of southeast France. TOC content was high (ca. 3-8%) throughout the Goguel, the Paquier and Kilian levels. Archaeal-derived hydrocarbons such as 2,6,15,19-tetramethylicosane (TMI) and 2,6,10,15,19-pentamethylicosane (PMI) were present in the OAE1b sediments, as reported previously [Kuypers, M.M.M., Blokker, P., Erbacher,J., Kinkel, H., Pancost, R.D., Schouten, S., Sinninghe Damste, J.S., 2001. Massive expansion of marine archaea during a mid-Cretaceous oceanic anoxic event. Science 293, 92-94]. However, we did not detect these archaeal biomarkers in the Goguel level, confirming that the prevalence of archaea producing TMI and PMI was restricted to OAE1b. (C) 2008 Elsevier Ltd. All rights reserved.
  • SAWADA Ken
    Researches in organic geochemistry 日本有機地球化学会 23 (24/) 13 - 22 1344-9915 2008 [Refereed][Invited]
     
    Organic geochemical records for devastation of terrestrial ecosystem in the environmental disturbance events of Permian-Triassic boundary (PTB) are reviewed. Paleontological and geological (sedimentological) investigations for terrestrial ecosystem and environment in PTB have provided information for collapse and devastation of ecosystem in the supercontinent (Pangea), such as dieback of woody vegetation, massive loss of rooted plant, repopulation of herbaceous lycopsid, proliferation of fungal remain, cease of peat formation, and increased mutagenesis of spore and pollen. Recent studies of biomarker and kerogen reported that remarkable abundances of aromatic furans in marine sedimentary sequence of PTB showed organic geochemical evidence of massive soil erosion due to destruction of terrestrial vegetation. Sedimentary aromatic furan is possibly derived from polysaccharide in soil, whereas aromatic furan is also known to be synthesized as secondary metabolite of extant lichen. Thus, source(s) of sedimentary aromatic furan is still controversial, and further examination is necessary.
  • 有機地球化学からみた白亜紀中期、海洋無酸素事変1aおよび1bにおける古生態・古環境変動.
    岡野和貴, 沢田健
    Researches in Organic Geochemistry 23 (24/) 23 - 32 2008 [Refereed][Not invited]
  • Kazuki Okano, Ken Sawada
    GEOCHEMICAL JOURNAL 42 (2) 151 - 162 0016-7002 2008 [Refereed][Not invited]
     
    Biomarker analyses of aliphatic and aromatic hydrocarbons were conducted on the upper and lower parts of individual mudstones in a turbiditic sequence of the Miocene Kawabata Formation, Yubari, central Hokkaido, Japan. The relative abundances of terrigenous biomarkers such as long-chain n-alkanes, C-29 steranes and oleanenes as well as biomarkers produced in coastal areas such as dinosteranes tend to be higher in the lower parts of mudstones than those of the upper ones in the turbiditic sequence. Also, pristane/phytaile ratios, which are proxies for depositional environment, significantly vary between the upper and lower parts of mudstones in the turbiditic sequence. These results suggest that these variations reflect the types and phases of transport and redeposition by turbidity systems rather than postdepositional diagenesis. Such heterogeneous distributions in most of biomarker compositions within the mudstone layers may lead to a severe bias for reconstructing paleoenvironment and paleoecology. Nevertheless, the higher plant parameters (HPPs) such as the retene/cadalene ratios are consistently homogenous within the mudstones. Moreover, paleovegetation reconstructed from HPPs are concordant with a previous paleobotanical study. Thus, it seems that these biomarker records in the turbidite sediments are reliable and strongly applicable for reconstructing terrestrial paleovegetation.
  • Nakamura Hideto, Sawada Ken
    Researches in Organic Geochemistry 日本有機地球化学会 22 (0) 31 - 42 1344-9915 2007 [Refereed][Not invited]
     
    The chemical compositions of woody fossil fragments collected by picking manually and density centrifugation from sandstones of the Lower Cretaceous Yezo Group in Oyubari, central Hokkaido, Japan were analyzed by KOH/methanol hydrolysis (saponification) after solvent extraction. Organic compounds bound in macromolecules of the woody fragments with ester bonds, obtained by saponification, were mainly composed of short-chain (C14 to C18) fatty acids and series of n-alkanols ranging from C12 to C28 homologues. These ester bound constituents are attributed to moieties of polyester parts of selectively preserved resistant macromolecule like cutin or suberin. Even carbon-number predominance was observed in both compounds, which indicated that biological components were well preserved. The bound fatty acids showed similar distribution patterns among all samples, indicating that these moieties might have been altered by strong diagenetic processes. On the other hand, the distribution patterns of n-alkanols significantly varied. In particular, those of long-chain (>C20) n-alkanols varied possibly depending on plant taxonomy. Thus, we suggest that these parameters are strongly useful as molecular paleobiological indicators for chemotaxonomic analyses. Also, the distributions of short-chain n-alkanols and the ratios of short to long-chain homologues are presumably useful indicators for diagenesis, taphonomy and environment.
  • Ken Sawada
    ISLAND ARC 15 (4) 517 - 536 1038-4871 2006/12 [Refereed][Not invited]
     
    Organic petrological observations of kerogen macerals and organic geochemical analyses of carbon isotopes of kerogen macerals and biomarkers were conducted on Neogene neritic sediments of the Takafu syncline area of central Japan. The Senmi, Sakainomiya and Lower Shigarami Formations in that area were deposited at the neritic provinces on the southern edge of the paleo-Japan Sea during the Late Miocene to Early Pliocene. Sedimentary organic matter in these formations was almost terrigenous in origin. Changes in kerogen maceral compositions reflect sedimentological and tectonic histories evaluated in previous studies from sedimentary facies and paleontology. It was found that carbon isotope ratios (delta C-13) of kerogen macerals increased from -28 parts per thousand to -25 parts per thousand from the Sakainomiya to the lower part of the Lower Shigarami Formations. The cause of that increase was presumably the expansion of C-4 plants into southwest Japan. The timing was concordant with that of the expansion of C-4 plant grasslands in East Asia. The oxicity (oxic to anoxic) conditions of sea bottoms evaluated from pristane/phytane ratios varied. Particularly, in the lower part of the Senmi Formation, layers in which no steroid biomarkers could be detected were found, and had presumably formed under oxic conditions when strong biodegradation had occurred. Concentrations of regular (C-27-C-29) steranes and dinosteranes were higher in the Sakainomiya and Lower Shigarami Formations. This indicates that dinoflagellates-dominant primary productions were higher at those stages. In addition, concentrations of diatomaceous biomarkers such as C-26 norsterane increased from the Lower Shigarami Formation, thus adding diatoms to the major producers. Furthermore, similar associations between the increases of delta C-13 values of kerogen macerals and concentrations of diatomaceous biomarkers were observed in the Takafu syncline area. Thus, the expansion of C-4 plants was possibly associated with the high production of diatom in the shallow-marine areas of the paleo-Japan Sea during the Neogene Period.
  • 岡野和貴, 沢田健
    Researches in organic geochemistry 有機地球化学会 21 49 - 58 1344-9915 2006 [Refereed][Not invited]
  • K Kaiho, ZQ Chen, T Ohashi, T Arinobu, K Sawada, BS Cramer
    PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY 223 (1-2) 172 - 180 0031-0182 2005/07 [Refereed][Not invited]
     
    Palaeozoic life was severely affected in a pair of mass extinction events at the beginning (earliest Lopingian, 260 million years ago) and the end (251 million years ago) of the Late Permian. However, the biological and geochemical record of the earliest Lopingian crisis remains poorly constrained. We present analyses of strata in South China showing that a negative anomaly of stable carbon isotope ratios accompanied an abrupt extinction of marine faunas at the beginning of the Late Permian, similar to patterns observed at the end-Permian and the end-Cretaceous (65 million years ago) extinction events. (c) 2005 Published by Elsevier B.V.
  • 堆積岩中のC27-C30五環性トリテルペノイドのGC/MS解析
    沢田健
    Researches in Organic Geochemistry 20 65 - 76 2005 [Refereed][Not invited]
  • Ken Sawada, Yoshihiro Shiraiwa
    PHYTOCHEMISTRY 65 (9) 1299 - 1307 0031-9422 2004/05 [Refereed][Not invited]
     
    The lipid classes and unsaturation ratios of long-chain alkenones (nC(37)-C-39), related alkyl alkenoate compounds (nC(37)-C-38) and alkenoic acids (nC(14)-C-22) were determined in isolated membrane and organelle fractions of Emiliania huxleyi. The percentage distribution of these compounds was predominantly high in the endoplasmic reticulum (ER) and coccolith-producing compartment (CPC)-rich membrane fraction, although alkenones and alkenoates could be detected in all membrane fractions. In particular, the alkenones were mainly located in CPC, since their distribution was closely correlated with that of uronic acids which are markers of CPC. In contrast, the alkenoic acids seemed to be mainly located in chloroplast (thylakoid)-rich fractions. The alkenone unsaturation ratio and the ratio of alkenoates to alkenones were similar in all fractions, while the unsaturation ratio of alkenoic acids in the thylakoid-rich and plasma membrane (PM)/Golgi body-rich fractions was overwhelmingly higher than that in the ER/CPC-rich fractions. Thus, alkenoic acids seemed to be typical membrane-bound lipids, and could be closely related to photosynthesis and involved in regulating membrane fluidity and rigidity in E. huxleyi. It is presumed from these results that the alkenones and alkenoates were membrane-unbound lipids that might be associated with the function of CPC. (C) 2004 Elsevier Ltd. All rights reserved.
  • Suzuki, N, Saito, H, Sawada, K
    Proceedings of ODP Scientific Results 190 (196) 1 - 10 2004 [Refereed][Not invited]
  • Ken Sawada
    Photo/Electrochemistry & Photobiology in Environment, Energy & Fuel 2004 149 - 164 2004 [Refereed][Invited]
  • Ken Sawada
    Photo/Electrochemistry & Photobiology in Environment Energy & Fuel, 2003 Research Signpost 131 - 146 2003 [Refereed][Invited]
  • A Rosell-Mele, E Bard, KC Emeis, JO Grimalt, P Muller, R Schneider, Bouloubassi, I, B Epstein, K Fahl, A Fluegge, K Freeman, M Goni, U Guntner, D Hartz, S Hellebust, T Herbert, M Ikehara, R Ishiwatari, K Kawamura, F Kenig, J de Leeuw, S Lehman, L Mejanelle, N Ohkouchi, RD Pancost, C Pelejero, F Prahl, J Quinn, JF Rontani, F Rostek, J Rullkotter, J Sachs, T Blanz, K Sawada, D Schulz-Bull, E Sikes, C Sonzogni, Y Ternois, G Versteegh, JK Volkman, S Wakeham
    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 2 2000GC141  1525-2027 2001/07 [Refereed][Not invited]
     
    Measurements of the U-37(K') index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface temperature and haptophyte (mainly coccolith-bearing species) primary productivity, respectively. An important aspect of these studies is to be able to compare reliably data obtained by different laboratories from a wide variety of locations. Hence the intercomparability of data produced by the research community is essential. Here we report results from an anonymous interlaboratory comparison study involving 24 of the leading laboratories that carry out alkenone measurements worldwide. The majority of laboratories produce data that are intercomparable within the considered confidence limits. For the measurement of alkenone concentrations, however, there are systematic biases between laboratories, which might be related to the techniques employed to quantify the components. The maximum difference between any two laboratories for any two single measurements of U-37(K') in sediments is estimated, with a probability of 95% to be <2.1<degrees>C. In addition, the overall within-laboratory precision for the U-37(K') temperature estimates is estimated to be <1.6<degrees>C (95% probability). Similarly, from the analyses of alkenone concentrations the interlaboratory reproducibility is estimated at 32%, and the repeatability is estimated at 24%. The former is compared to a theoretical estimate of reproducibility and found to be excessively high. Hence there is certainly scope and a demonstrable need to improve reproducibility and repeatability of U-37(K') and especially alkenone quantification data across the community of scientists involved in alkenone research.
  • Joan O. Grimalt, Juergen Rullkoetter, Marie-Alexandrine Sicre, Roger Summons, John Farrington, H. Rodger Harvey, Miguel Goni, Ken Sawada
    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 1 1525-2027 2000/11 [Refereed][Not invited]
     
    The literature pertaining to C-37 alkenone and C-37 and C-38 alkenoate production and diagenesis has been reviewed and evaluated for issues that might jeopardize their usefulness in paleotemperature estimation. We also examined the use of the C-37 alkenones as paleoproductivity indicators, the stability of their delta C-13 isotopic compositions, and their incorporation into the nonsolvent extractable organic matter fraction. Biological transformation of organic matter by bacteria and zooplankton does not appear to cause significant changes to the ratio of C-37.2 and C-37:3 alkenones, but there are major alterations in the relative composition of alkenoates. Studies of water column processes and postdepositional sedimentary changes indicate overall stability in the C-37:2/(C-37:2 + C-37:3) ratio, leading to effective preservation of the paleotemperature signal. This is not the case for alkenoates, and there also appear to be some doubts about the dependence between sea surface temperature and the sedimentary abundance of the C-37:4 alkenone. C-37 alkenones may provide useful qualitative estimates of marine paleoproductivity. Although these compounds are apparently only derived from Haptophycea, changes in their quantitative composition might reflect changes in nutrient availability that on sedimentary timescales should also be generally significant of other algal species. One caveat is that in highly productive upwelling systems, productivity may be expressed mostly in diatom growth and thus not measurable by the C-37 alkenones. No changes in delta C-13 C-37 alkenone composition are observed upon zooplankton ingestion. Although this is expected from a theoretical perspective, further studies are encouraged in order to fully assess the stability of the isotopic signal during C-37 alkenone diagenesis. Finally, alkenones bound in the nonextractable fraction of sedimentary organics have not been adequately studied and further work is required to clarify any possible correspondence with a temperature signal.
  • Ken Sawada, Akira Shimoyama
    Researches in Organic Geochemistry 日本有機地球化学会 15 51 - 56 1344-9915 2000 [Refereed][Not invited]
     
    Aliphatic and aromatic hydrocarbons, and fatty acids were detected from a stone excavated from an archaeological pit in Inadaira site, Aomori Prefecture, Japan. Polycyclic aromatic hydrocarbons (PAHs) of pyrolytic origin were not detected in carbonized material adhered on the surface of the stone sample and in soil (soil sample) which covered the stone. Shorter carbon-chain (22) n-alkanes found on the stone sample were probably associated with allochthonous living organisms. Likewise, the tetradecanoic, hexadecanoic and cis-9 hexadecenoic acids were relatively abundant in the sample, indicating that the allochthonous materials were supplied and well preserved on the surface. In the soil sample, the molecular distribution patterns of n-alkanes and fatty acids were nearly similar to those reported for the typical forest soil and therefore, they were mainly derived from the terrestrial higher plants. These results indicate that the stone has not experienced high temperature heating and do not support the archaeologists' speculation that the pit was used as a kiln. It is presumed that the pit was possibly used as a non-heating place for storage of foods etc.
  • Productivity of Gephyrocapsacean algae revealed from long-chain alkenones and alkyl alkenoates in the northwestern Pacific off Japan.
    Ken Sawada, Hisatake Okada, Yoshihiro Shiraiwa, Nobuhiko Handa
    In: Dynamics and Characterization of marine organic matter (eds, N. Handa, E. Tanoue and T. Hama) TERRAPUB/Kluwer 187 - 211 2000 [Refereed][Not invited]
  • Junko Hamanaka, Ken Sawada, Eiichiro Tanoue
    ORGANIC GEOCHEMISTRY 31 (11) 1095 - 1102 0146-6380 2000 [Refereed][Not invited]
     
    The production rates of C-37 alkenones in the euphotic zone of Sagami Bay, Japan Evert determined by the C-13-labeling technique in conjunction with gas chromatography-mass spectrometry. The maximum in the alkenone production rate (C-37:2 plus C-37:3 alkenones) was observed at 5 m depth and the specific production rate, calculated from the rate of production relative to standing stock in suspended particles, was 0.64 day(-1) at this depth. Temperature, based on the newly-produced alkenone unsaturation index (U-37(k)), was close to in situ temperatures at the depth where alkenones production was active. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • Ken Sawada, Nobuhiko Handa
    NATURE 392 (6676) 592 - 595 0028-0836 1998/04 [Refereed][Not invited]
     
    The Kuroshio current is the strong northwestern component of the subtropical North Pacific Ocean gyre, and advects a large amount of heat from the tropics to northern mid-latitudes, The Kuroshio has bimodal stationary now patterns, with small and large meander paths east of central Japan(1,2) which switch on annual and decadal timescales(3,4). These switches seem to be caused by changes in current velocity and volume transport of the North Equatorial Current that are associated with variations in the trade-wind intensity in the eastern equatorial North Pacific Ocean(5,6). Here we present alkenone-derived sea surface temperature records at multicentennial resolution from sediment cores from the Nishishichitou ridge off central Japan. These 25,000-year records show that the Kuroshio path has also fluctuated on millennial timescales, This variability resembles that of the subtropical high pressure of the North Pacific, reconstructed from terrestrial pollen distributions, water levels in North American lakes, and marine micropalaeontological records(7). Together, these data indicate that climate variability off central Japan over the past 25,000 years may be part of a circum-Pacific phenomenon, reflecting the rate of subtropical surface circulation in the North Pacific Ocean.
  • Ken Sawada, Nobuhiko Handa, Takeshi Nakatsuka
    MARINE CHEMISTRY 59 (3-4) 219 - 234 0304-4203 1998/01 [Refereed][Not invited]
     
    Sinking particles collected from year-long time-series sediment traps at 1674, 4180, 5687 and 8688 m depths, the underlying bottom sediment at 9200 m depth, and suspended particles from surface and subsurface waters in the northwestern North Pacific off Japan were analyzed for long-chain alkenones and alkyl alkenoates (A&A) which are derived mainly from Gephyrocapsacean algae, especially Emiliania huxleyi and Gephyrocapsa oceanica. Alkenone temperature records in sediment trap samples at 1674 m were almost similar to observed sea surface temperatures (SST) with a time delay of one half to one full month. However, alkenone temperatures in trap samples were about slightly lower than measured SST in late spring to early fall. The lowering might be caused by formation of the seasonal thermocline. Nevertheless, these temperature drops observed in trap samples were smaller than those actually observed in a subsurface layer off central Japan. Vertical profiles of A&A concentrations and all;enone temperatures in suspended particles collected from the subsurface waters in early fall indicated that these compounds were produced mostly in a surface mixed layer above the depth of the chlorophyll maximum even in warm seasons. These results suggested that alkenone temperatures strongly reflected SST rather than the temperatures of thermocline waters in these study areas even in such a warm season. Pronounced maxima in A&A fluxes found in sediment trap samples at 1674 m in late spring to summer showed that A&A productions were highest during the periods of spring bloom, according to a time delay between alkenone temperatures and observed SST. Seasonal patterns of alkenone records in trap samples at 4180 and 5687 m could also preserve SST signals well, suggesting that A&A in deep sea waters were mainly derived from primary products in the surface layer. A&A fluxes tended to decrease with water depth, and the ratios of A&A to particulate organic carbon (POC) rapidly decreased in underlying bottom sediment. This clearly indicates that A&A were decomposed and diluted by other refractory organic materials in either the water column or the sediment-water interface. However, A&A compositions were consistently uniform between the trap samples and the underlying bottom sediments, so that A&A could not qualitatively alter during early diagenetic processes. (C) 1998 Elsevier Science B.V.
  • Ken Sawada, Nobuhiko Handa, Yoshihiro Shiraiwa, Akiko Danbara, Shigeru Montani
    ORGANIC GEOCHEMISTRY 24 (8-9) 751 - 764 0146-6380 1996/08 [Refereed][Not invited]
     
    Long-chain (n C-37-C-39) alkenones and (n C-37-C-38) alkyl alkenoates in marine sediments are derived mainly from two marine coccolithophorids, Emiliania huxleyi and Gephyrocapsa oceanica. Laboratory cultured strains of E. huxleyi (strain EH2) and G. oceanica (strain GO1), isolated from the Great Barrier Reef and Mutsu Bay in northern Japan (41 degrees N, 141 degrees E), respectively, were cultured at 10 degrees C, 15 degrees C, 20 degrees C, 22 degrees C, 25 degrees C, 28 degrees C and analyzed for C-37 to C-39 alkenones, C-36 methyl alkenoate (FAME) and C-36 ethyl alkenoate (FAEE). Results obtained indicated significant differences in the alkenone and alkyl alkenoate profiles between these two algal species. The ratios of FAEE to C-37 alkenones (EE/K37) and C-38 alkenones (EE/K38) in G. oceanica were higher than those ill E. huxleyi and, for both algal species, these ratios showed strong negative nonlinear exponential correlations when plotted against the unsaturation index of C-37 alkenones (U-37(k)). Using fitted equations for these relationships, the relative abundance of E. huxleyi and G. oceanica in the sediment samples from the northwest North Pacific and the coastal and inland waters of Japan were estimated and compared with direct microscopic determinations. E. huxleyi comprised more than 80% of the sedimentary coccolith assemblage in the open ocean, whereas G. oceanica was exclusively dominant in the inland waters. These results almost agreed with microscopic counts of these coccoliths occurring in the sediment samples. In the light of these findings, we suggest that there is a possibility that the relative abundance of E. huxleyi and G. oceanica in sediments may be estimated using nonlinear exponential calibrations based on EE/K37 to U-37(k) and EE/K38 to U-37(k) regressions. Copyright (C) 1996 Elsevier Science Ltd
  • Sawada T., Handa N., Shiraiwa Y., Danbara A.
    Researches in Organic Geochemistry 日本有機地球化学会 10 21 - 26 1344-9915 1995 [Refereed][Not invited]
  • Akiyama A., Sawada K., Knoll A. H.
    Researches in Organic Geochemistry 日本有機地球化学会 9 7 - 9 1994 [Refereed][Not invited]
  • 沢田健, 秋山雅彦
    石油技術協会誌 59 (3) 244 - 255 0370-9868 1994 [Refereed][Not invited]
  • 沢田健, 有田陽子, 中村俊夫, 秋山雅彦, 亀井節夫, 中井信之
    地球科学 46 133 - 142 1992 [Refereed][Not invited]

MISC

Books etc

  • 日本古生物学会 (Contributor化学化石による古環境復元 ほか2項)
    丸善出版 2023/01 (ISBN: 9784621307588) xxiv, 754p, 図版 [8] p
  • 北海道大学自然科学実験編集委員会 編 自然科学実験
    沢田健 (Contributor地球惑星科学系実験 堆積物からさぐる地球の環境．pp.166-175)
    学術図書出版社 2016
  • Handbook of Algea - Their Diversity and Utilization
    SAWADA Ken (ContributorAlkenone)
    NTS Inc. 2012 (ISBN: 9784864690027) 824 196-201
  • 地球惑星科学入門
    北海道大学出版会 2010
  • 沢田健, 綿貫豊, 西弘嗣, 栃内新, 馬渡峻輔 (Editor)
    北海道大学出版会 2008 (ISBN: 9784832981836) 272
  • 地球の変動と生物進化
    沢田健, 綿貫豊, 西弘嗣, 栃内新, 馬渡峻輔 (Editor)
    北海道大学出版会 2008 (ISBN: 9784832981843) 300

Presentations

  • Asahi Hiroyasu, Sawada Ken
    Annual Meeting of the Geological Society of Japan  2022  The Geological Society of Japan
     
    1.はじめに 北海道の中新世には，島弧–島弧衝突により南北約 400 km，幅数 10 kmにわたる地域に狭長なフォアランド堆積盆が形成された。日高地域にはフォアランド堆積盆南部に位置する日高堆積盆を充填した泥質-砂質堆積岩が幅広く分布している(Kawakami.2013)。日高堆積盆が充填された中期-後期中新世には、8-7MaのEASMの弱化や東南極氷床の拡大により、複数回の寒冷化が東アジアから北西太平洋で発生したことが東シナ海や日本海、北太平洋外洋域での海洋掘削コアを用いた研究により明らかになりつつある(Matsuzaki et al.,2020)。一方、日本列島の太平洋沿岸域や北部域での古海洋情報は不足しており、日高堆積盆堆積岩から得られる古環境データは不足した領域の古海洋情報を補完できると考えている。本研究では中期-後期中新世までの堆積岩が連続的に露出する波恵川荷菜層の泥質堆積岩から長鎖アルケノンを検出例し、アルケノン古水温指標から復元した当時の海洋表層水温とその定量分析による海洋基礎生産の変動について報告する。 2.試料と手法 本試料が採取された波恵川は北海道日高町に位置する。波恵川には後期中新統荷菜層が露出しており、上流域では不整合により二風谷層上部が分布している。岩相は主に泥岩から砂質泥岩で構成されており、時折平行葉理を持つタービダイト層を挟む。また上位層準へ行くに従い粗粒化する傾向が見られ、最上部ではチャネル充填堆積物とされる礫層が卓越する。珪藻群集組成解析による波恵川荷菜層堆積年代では9.7-3.5Maと見積もられており(丸山ほか 2019)、後期中新世から鮮新世初頭にかけての堆積岩が連続して露出すると考えられる。 バイオマーカー分析は荷菜層泥岩から遊離態成分を抽出した後、GC-MS、GC-FIDによって測定・解析を行った。アルケノン古水温復元ではMüller et al.(1998)の換算式SST = (UK’37 －0.044) / 0.033から古水温を算出した。 3.結果と考察 波恵川荷菜層からはタービダイト性砂岩以外の全ての泥質堆積岩からハプト藻由来の有機成分であるアルケノンが得られた。アルケノンから見積もった海洋表面温度（SSTUK）は9.3-8.7Maから中新世末まで一貫した低下を示し、中新世末期からは細かい増減変動を見せる。SSTUKは9.3Maから8.0Maでは平均26.0℃、7.7Maから6.5Maでは22.3℃、6.5Ma以降では18.9℃と推算された。これらの結果から日高堆積盆では比較的高温だったSSTが8.7Ma以降急な水温低下が発生しており、これまで報告されてきた7.7Maから6.6MaにかけてEASMの弱化による日本海域でのSST低下と連動すると考えられる。また、6.5Ma以降の寒冷化は太平洋域(ODP site 1208)から報告された黒潮流弱化による寒冷化の影響が示唆されている(Matsuzaki et al.,2020)。日高堆積盆は日本海と太平洋双方の影響を受けてきた海域と考えられるが、その影響の度合は時代により異なることが本研究の結果から示唆され、中新世/鮮新世境界において、日本海側の影響を強く受けるフェーズから太平洋側の影響を強く受けるフェーズへ移行したことが推察される。 C37 アルケノンの濃度結果では、寒冷化を示す層準にて相対的に高い値を示す傾向が見られた。特に6.5Ma以降の層準では堆積物1gあたり最大0.45μgを示す。これらは海洋表層の冷却による海洋循環の強化による基礎生産量の増大を示唆すると考えられる。 4.参考文献 ・Kawakami. (2013) InTech 131-155. ・丸山ほか (2019) 山形大学紀要(自然科学) 19 15-24. ・Matsuzaki et al. (2020) Geology 48 (9) 919-923. ・Muller et al.(1998) Geochim. Cosmochim. Acta 62(10) 1757-1772.
  • Palynomorph assemblage in sedimentary rocks of the Mesoproterozoic Qaanaaq Formation from northwestern Greenland.
    原勇貴, 安藤卓人, 沢田健
    日本地球惑星科学連合大会予稿集(Web)  2020
  • 池田雅志, 沢田健, 安藤卓人, 中村英人, 高嶋礼詩, 西弘嗣
    日本地球惑星科学連合大会予稿集(Web)  2019
  • Sawada Ken, Aoyagi Chiaki, Kobayashi Madoka, Furota Satoshi, Nakamura Hideto
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2019  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上高等植物に由来するテルペノイドは植物分類によって多様な構造を持ち、その起源をより限定できるため、陸源物質の海洋への輸送過程、その供給源や後背地の植生などを評価するための強力な指標となり得る。深海堆積物には現生植物が生合成する官能基をもった生体テルペノイドがおもに検出されるが、続成・熟成作用を受けたテルペン炭化水素のような続成テルペノイドも極微量ながら有意に見出される。このような続成テルペノイドは、中国内陸部の砂漠地域などの後背地において続成作用を受けた高熟成堆積岩・土壌を供給源としていて、大気輸送ダストとして太平洋にもたらされていることが推定されている。また、森林火災などの燃焼によってもテルペン炭化水素が生成され、おもに大気経由で海洋に輸送されている。本講演では、北太平洋と北大西洋の堆積物中でのテルペン炭化水素を比較して、それらの起源と輸送過程、さらにそれらを用いた大気輸送指標および古気候学指標としての有用性について議論する。
  • Ando Takuto, Hirose Kotaro, Nakamura Hideto, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2019  GEOCHEMICAL SOCIETY OF JAPAN
     
    瀬戸内海堆積物を用いて珪藻の殻含量を17種類のステロイドそれぞれの割合と比較したところ，campesterol 比(%)と正相関し，最も相関係数が高かった。campesterolは，ostreasterolとbrassicasterolに次いで，生合成する珪藻の種数が多いステロイドである。ostreasterolとbrassicasterolは，それぞれ渦鞭毛藻と円石藻も生合成する成分であり，珪藻以外の主要な生産者の寄与も反映して変化した結果，珪藻殻と顕著な相関が見られなかったのだと考えられる。一方，珪藻殻含量と渦鞭毛藻指標であるdinosterol比(%)は，逆相関の関係にあった。近似線から大きく外れる試料は，相対的に珪藻殻量が少なく，採取地点は陸に近い場所であった。保存バイアスの影響を考慮する必要性はあるものの，より沖側の海域では珪藻と渦鞭毛藻の単純な競争関係で有機物埋積が説明でき，陸に近い場所では珪藻生産が渦鞭毛藻以外の第三の生物群によって抑えられている可能性がある。
  • Hattori Yuki, Sawada Ken, Ando Takuto, Nakamura Hideto, Hirose Kotaro
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2019  GEOCHEMICAL SOCIETY OF JAPAN
     
    海跡湖である島根県中海で得られた堆積物コアにおいて過去約600年間に渡る長鎖アルケノン組成とアルケノン不飽和度を測定し、汽水環境におけるアルケノン生産種の推定と細かい年代間隔での古水温復元を試み、中海周辺の気候変動について検討した。アルケノン組成はコア深度18cmを挟んだ上位と下位で顕著に異なり、その特徴から下位では外洋や沿岸に広く分布する Emiliania huxleyi や Gephyrocapsa oceanica が、上位では内陸塩湖や沿岸に分布する Ruttnera lamellosa が主なアルケノン生産種と推定された。復元された水温変動は江戸時代の4大飢饉や古文書記録に基づく日本の17世紀以降の気候の時代区分と大局的に一致し、中海におけるアルケノン古水温計の応用により詳細な古環境変遷の復元が可能となった。
  • Nakamura Jinya, Sawada Ken, Ikeda Masashi A, Nakamura Hideto, Tsukagoshi Minoru
    Annual Meeting of the Geological Society of Japan  2019  The Geological Society of Japan
  • Tateshita Yuki, Sawada Ken, Ando Takuto, Nakamura Hideto, Hayashi Keiichi
    Annual Meeting of the Geological Society of Japan  2019  The Geological Society of Japan
  • 安藤卓人, 沢田健
    日本地質学会学術大会講演要旨  2018/09
  • 服部由季, 沢田健, 安藤卓人, 中村英人, 廣瀬孝太郎
    日本地質学会学術大会講演要旨  2018/09
  • Ikeda Masashi, Sawada Ken, Ando Takuto, Nakamura Hideto, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2018  The Geological Society of Japan
  • 池田雅志, 沢田健, 安藤卓人, 中村英人, 高嶋礼詩, 西弘嗣
    日本地球惑星科学連合大会予稿集(Web)  2018
  • 服部由季, 沢田健, 安藤卓人, 中村英人, 廣瀬孝太郎
    日本地球惑星科学連合大会予稿集(Web)  2018
  • 安藤卓人, 沢田健
    日本古生物学会例会講演予稿集  2017/01
  • Ando Takuto, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2017  The Geological Society of Japan
  • Tateshita Yuki, Sawada Ken, Ando Takuto, Nakamura Hideto, Hayashi Keiichi
    Annual Meeting of the Geological Society of Japan  2017  The Geological Society of Japan
  • Nakamura Hideto, Ando Takuto, Hirose Kotaro, Asaoka Satoshi, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2017  GEOCHEMICAL SOCIETY OF JAPAN
     

  • Tateshita Yuki, Sawada Ken, Miyata Yuma, Nakamura Hideto, Hayashi Keiichi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2017  GEOCHEMICAL SOCIETY OF JAPAN
     

  • 安藤卓人, 沢田健
    日本地球化学会年会要旨集(Web)  2017
  • Toyama Kotaro, Nakase Chiharu, Sakurai Goto Akiko, Sawada Ken, Paytan Adina, Hasegawa Takashi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2017  GEOCHEMICAL SOCIETY OF JAPAN
     

  • 新家弘也, 中村英人, 沢田健, HAIG H, TONEY J, LEAVIT P, 鈴木石根, 白岩善博
    マリンバイオテクノロジー学会大会講演要旨集  2016/05
  • 廣瀬孝太郎, 中村英人, 安藤卓人, 浅岡聡, 沢田健
    日本地球惑星科学連合大会予稿集(Web)  2016
  • Nakamura Hideto, Ando Takuto, Hirose Kotaro, Asaoka Satoru, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2016  GEOCHEMICAL SOCIETY OF JAPAN
     

  • 安藤卓人, 沢田健, 高嶋礼詩, 西弘嗣
    日本地球惑星科学連合大会予稿集(Web)  2016
  • Ando Takuto, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2015  GEOCHEMICAL SOCIETY OF JAPAN
     
    堆積岩中に普遍的に存在する三芳香環ステロイドを始めとした三芳香環ステロイドの同定を詳細に検討し，それらを用いた指標から海洋基礎生産者群集を復元した結果を報告する。<br><br>南東フランス・ボコンティアン堆積盆の白亜系海洋無酸素事変層準と北海道大夕張地域と苫前地域の白亜系蝦夷層群から採取した堆積岩試料を用い，GC-MSを用いて芳香族ステロイドの分析を行なった。三芳香環ステロイドの分離と同定は2種類の極性と長さの異なるカラムを用いることで可能にした。三芳香環ジノステロイドを用いたTADS（渦鞭毛藻指標）とC<SUB>27</SUB> TAS（円石藻指標）を提案した。南東フランス試料では白亜紀における円石藻と渦鞭毛藻の競争関係とOAE極相期の富栄養で成層化した海洋における渦鞭毛藻の繁茂が示された。一方で北海道試料からは，現在同様に沿岸に近い海洋表層において渦鞭毛藻の生産性が高かったことが示唆された。
  • Ando Takuto, Sawada Ken, Nakamura Hideto, Miyata Yuma, Omatsu Keita, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2015  The Geological Society of Japan
  • Ando Takuto, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2015  The Geological Society of Japan
  • 中村英人, 竹田真由美, 沢田健, 高野淑識
    日本地球惑星科学連合大会予稿集(Web)  2015
  • 宮田遊磨, 沢田健, 池田慧, 中村英人, 高橋正道
    日本地球惑星科学連合大会予稿集(Web)  2015
  • Nakamura Hideto, Sawada Ken, Araie Hiroya, Suzuki Iwane, Shiraiwa Yoshihiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2015  GEOCHEMICAL SOCIETY OF JAPAN
     
    湖沼のアルケノン生産種として Isochrysidaceae 科の <I>Ruttnera</I> 属, <I>Isochrysis</I> 属, <I>Tisochrysis</I> 属に近縁の遺伝子配列が報告されている。Tisochrysis 属のアルケノン不飽和度-水温換算式を求めるために <I>T. lutea</I> CCMP463 株および NIES2590 株の培養実験を行ったところ、これらの株は 15℃-35°C でよく増殖し、4不飽和アルケノンを合成せず、2不飽和アルケノンと3不飽和アルケノンの比を大きく変化させて水温に応答することが明らかになった。本研究で得られた <I>T. lutea</I> の換算式は沿岸や湖沼の古水温復元に必要なアルケノン生産種の系統と水温換算式の対応関係に新たなバリエーションを与える。
  • Miyata Yuma, Sawada Ken, Nakamura Hideto
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2015  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上植物が持つ抵抗性高分子はその構造や構成するモノマーの組成が植物の種類や器官、生育環境によって変化することが知られている。植物化石を構成する高分子の脂肪族部分は主にクチンを含む表皮組織が選択的に保存されたものだと考えられている。化石高分子を構成するアルキル脂質の組成を調べることで、化石の分類や堆積環境、生育した当時の古環境に関する情報が得られる可能性がある。しかし、植物生体が持つクチン酸の組成が化石高分子にどのように反映されているのかは不明瞭である。本研究では、植物の表皮を構成する脂質がどのように保存・分解され化石高分子のアルキル脂質組成に反映されているのかを理解するため現生植物の葉の組織を用い加熱実験を行った。加熱実験により、一部の試料では難分解性のクチンよりもむしろワックスに由来するアルキル脂質のほうが加水分解性および非加水分解性の高分子成分として保存されていることが明らかになった。
  • Miyata Yuma, Sawada Ken, Ikeda Kei, Nakamura Hideto, Takahashi Masamichi
    Annual Meeting of the Geological Society of Japan  2015  The Geological Society of Japan
  • 安藤卓人, 沢田健, 高嶋礼詩, 西弘嗣
    日本地球惑星科学連合大会予稿集(Web)  2015
  • Ando Takuto, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2014  GEOCHEMICAL SOCIETY OF JAPAN
     
    北海道苫前地域の蝦夷層群堆積岩は低熟成で有機物の保存状態が良いが，このような低熟成な堆積岩と南東フランスVocontian堆積盆CTB層準の堆積岩から，藻類や陸上植物に由来する易分解性のトコフェロール（ビタミンE）を検出したので報告する。比較的低熟成なThomel層準の黒色頁岩試料，朱鞠内沢・大曲沢川の苫前地域試料の極性画分において，トコフェロール類が検出され，高熟成な大夕張地域白金沢試料からは全く検出されなかった。Thomel層準と大曲沢川ほとんどの試料でδ体が50％以上占め，朱鞠内沢試料ではα体が6～39％と比較的多く検出された。より低熟成な朱鞠内沢試料中においては，α体の分解が進んでおらず，組成の違いが生じた可能性がある。一方，各層準内での組成の変動については，堆積時のトコフェロール組成の違いを反映していると考えられる。
  • Takuto Ando, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2014  The Geological Society of Japan
  • Nakamura Hideto, Sawada Ken, Ando Takuto, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2014  The Geological Society of Japan
  • Ando Takuto, Nakamura Hideto, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2014  The Geological Society of Japan
  • Nakamura Hideto, Sawada Ken, Araie Hiroya, Shiraiwa Yoshihiro, Shiraiwa Yoshihiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2014  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸水のアルケノン生産種を含むグループであるハプト藻イソクリシス目（Isochrysidaceae） のアルケノン組成と系統の関係を明らかにするため、培養株7株の LSU rDNA 塩基配列を決定して分子系統解析を行い、これらの株のアルケノン組成を比較した。培養株は<I> Tisochrysis </I>と <I>Isochrysis </I>に分類され、<I>Tisochrysis </I>の株は、4不飽和アルケノンをほとんど持たない点が共通していた。一方で、<I>Isochrysis </I>のうち2株は4不飽和アルケノンを顕著に含み（%37:4 > 5）、2不飽和アルケノンの割合が少なかった。これらの特徴は先行研究のデータを加えても調和的であり、<I>Tisochrysis </I>と<I> Isochrysis </I>をよく区別する化学分類学的特徴である可能性が示唆された。
  • Abe Ryohei, Sawada Ken, Nakamura Hideto, Araie Hiroya, Suzuki Iwane, Shiraiwa Yoshihiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2014  GEOCHEMICAL SOCIETY OF JAPAN
     
    アルケノン合成種であるハプト藻の乾燥粉末を真空下で加熱すると、アルケノンの熱分解により生成されると考えられる炭化水素が生成されたことから、ハプト藻のバイオ燃料への応用が検討されている。<I>E. huxleyi</I>の培養試料の熱分解実験により、ハプト藻が合成する脂質の分解過程を検討し、バイオ燃料生産への応用を検討した。<I>E. huxleyi</I>の細胞試料は、加熱処理時間に伴いアルケノンが減少し、48時間以上では消失した。アルケノン粉末のみの場合、構造変化により多くの分子量の等しい異性体が検出された。モンモリロナイト添加実験では、C<SUB>13</SUB>～C<SUB>21</SUB>アルカンが主要成分として検出され、粘土鉱物の触媒効果によりアルケノンのクラッキング反応が促進されることを示した。ハプト藻脂質の炭化水素への熱分解効率を粘土鉱物の添加で促進できることを証明し、バイオ燃料生産における有用な方法を提案する。
  • Abe Ryohei, Sawada Ken, Nakamura Hideto, Araie Hiroya, Suzuki Iwane, Shiraiwa Yoshihiro
    Annual Meeting of the Geological Society of Japan  2014  The Geological Society of Japan
  • Miyata Yuma, Sawada Ken, Nakamura Hideto, Takahashi Masamichi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2014  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上高等植物はクチンやスベリン、リグニンといった特殊な抵抗性高分子を発達させてきた。これらの抵抗性高分子はその構造や構成するモノマーの組成が植物の種類や器官、成長段階などによって異なることが知られている。本研究では、白亜紀の植物組織の化石を用いアルカリ加水分解性脂質を分析し、古代堆積物中における抵抗性高分子の保存過程やその構成分子組成による化学分類を検討した。試料は白亜紀コニアシアンの双葉層群芦沢層から産出した小型化石を用いた。試料は遊離態成分を抽出後、その残渣をKOH/メタノールでアルカリ加水分解を行った。分解抽出された成分をGC/MSで分析・定量した。一部の非炭化試料からは典型的なクチン酸が顕著に検出され、白亜紀のような古代堆積物においても生体が持つクチン酸がよく保存されることがわかった。クチン酸の異性体組成は現生の植物を使った研究とも調和的であり、白亜紀の植物化石においても強力な化学分類指標として応用可能であることが立証された。
  • Miyata Yuma, Nakamura Hideto, Sawada Ken, Takahashi Masamiti
    Annual Meeting of the Geological Society of Japan  2014  The Geological Society of Japan
  • Ando Takuto, Sawada Ken, Nishi Hiroshi, Takashima Reishi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2013  GEOCHEMICAL SOCIETY OF JAPAN
     
    中期白亜紀は高海水準で非常に温暖な時代であり，有機物に富む黒色頁岩の堆積から幾度も海洋無酸素事変（Oceanic Anoxic Event; OAE）が起こったと推測されている。OAE1b（115～110Ma）は，テチス海を中心とした地域的なOAEであったとされ，Aptian/Albian境界を挟んで長期に渡って複数の黒色頁岩層が確認される。特に最盛期であるKilian層準・Paquier層準の黒色頁岩中からはメタン生成アーキア由来のPMI（2, 6, 10, 15, 19-ペンタメチルイコサン）などが検出されることから，「アーキアの海（Archaeal ocean）」が広がっていたとされている。本研究では，OAE1b層準の詳細なバイオマーカー分析を行い，アリルイソプレノイドに着目して起源を推察し，層準内におけるそれらの濃度変化から当時の海洋生態系の復元を試みた。
  • Miyata Yuma, Sawada Ken, Nakamura Hideto, Ikeda Kei
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2013  GEOCHEMICAL SOCIETY OF JAPAN
     
    白亜紀のような古代の堆積物中には陸上高等植物に由来する有機物片が普遍的に存在している．これらは主に植物体を構成するリグニンやクチンといった抵抗性高分子から構成され，化学的に安定で微生物分解や続成作用に抵抗性を持つため選択的に保存されたものである．これ等の有機化合物は分類群や生育環境によってその組成が特徴的に変化するため，化学分類指標や古環境指標などへの応用が期待されているが，地質時代の堆積物で検討した例は少ない．演者らの研究グループでは，白亜紀の陸上植物化石の化学分析により，抵抗性高分子を構成しているエステル結合態の飽和脂肪酸ユニットの組成が部位により異なることを明らかにし，化学分類指標を提案している（Ikeda et al., submitted）．本研究では，様々な植物組織が含まれる海成堆積物中の植物由来の不溶性有機物（ケロジェン）に応用し，古植生や陸域古環境の復元に適用できるかを検討した．
  • Nakamura Hideto, Sawada Ken, Araie Hiroya, Suzuki Iwane, Shiraiwa Yoshihiro
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2013  GEOCHEMICAL SOCIETY OF JAPAN
     
    アルケノンは海洋表層水温の指標として用いられるが、一部の海域や内陸湖において4不飽和アルケノンの割合（%C<SUB>37:4</SUB>）の増加と低塩分の関連性が指摘されてきた。本研究では、塩分がハプト藻のアルケノン組成に与える影響を確かめるため、4不飽和アルケノンに富む沿岸種 <I>Chrysotila lamellosa</I> を異なる塩分条件下（15-45 g/L）で培養し、アルケノン組成を解析した。<BR>アルケノン不飽和指数および、%K<SUB>37:4</SUB>は塩分によらずほぼ一定の値をとった。このことから、環境試料で報告される%C<SUB>37:4</SUB>と塩分の関係は、塩分変動に対する主なアルケノン生産種の個別の生理学的応答よりも、塩分変化と連動した他のアルケノン生産種の寄与を反映していると考えられる。
  • Kanoh Chisato, Sawada Ken, Nakamura Hideto, Shiraiwa Yoshihiro, Suzuki Iwane, Araie Hiroya
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2013  GEOCHEMICAL SOCIETY OF JAPAN
     
    ハプト藻は海洋における主要な基礎生産者であり、世界中の海洋において繁栄している。本研究では、ハプト藻イソクリシス目4種と、円石藻目8種の培養試料を用い、極性脂質画分を検出した。イソクリシス目ではC27ステロールであるCholesterolとC28ステロールのBrassicasterolが、円石藻目ではCholesterol、Brassicasterolに加えて23, 24-dimethylcholesta-5-en-3β-ol(C29)、Stigmasterol(C29)が検出され、ステロイド組成は目レベルで大きく異なる。また、<I>C. lamellosa</I>と<I>Cruciplacolithus neoheilis</I>株のみからC30ステロールが検出された。本研究では、ハプト藻のステロイド組成の種間の多様性を考察するとともに、限られた株から検出されたC30ステロールに着目してその意義を考察した。
  • 中村英人, 沢田健, 高嶋礼詩
    堆積学研究  2012/12
  • 中村英人, 沢田健, 高嶋礼詩
    日本堆積学会大会プログラム・講演要旨  2012/06
  • 中村英人, 沢田健, 池田慧, 高橋正道
    日本古生物学会年会講演予稿集  2012/06
  • 安藤卓人, 沢田健, 岡野和貴, 小刀禰宅朗, 横山龍, 西弘嗣, 高嶋礼詩
    日本堆積学会大会プログラム・講演要旨  2012/06
  • 安藤卓人, 沢田健, 西弘嗣, 高嶋礼詩
    日本古生物学会年会講演予稿集  2012/06
  • Ando Takuto, Sawada Ken, Nishi Hiroshi, Takashima Reishi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2012  GEOCHEMICAL SOCIETY OF JAPAN
     
    中期白亜紀の海洋では，無酸素水塊が拡大し有機物の大量埋積が起きたと考えられ，黒色頁岩の堆積によって示されるこれらの事変は「海洋無酸素事変（OAE）」と呼ばれている。OAE2は中期白亜紀で最も海洋の無酸素化が進んだイベントであり，汎世界的に黒色頁岩の堆積が認められている。OAE2の黒色頁岩からはシアノバクテリアや嫌気性光合成細菌由来のバイオマーカーが検出されることから，これらの基礎生産者が支配的な'Cyanobacterial ocean'であったと考えられてきた。しかし，最近の演者らの研究から，南仏のOAE2期においては，渦鞭毛藻の海洋生産への寄与を表すTDSI'（Triaromatic dinosterane index）が中期白亜紀のOAE層準中で最も高くなることが明らかになり，渦鞭毛藻の寄与もOAE2時に高まった可能性が示されている。本研究では，OAE2層準試料において詳細にバイオマーカー分析し，海洋環境変動や生物応答を復元することで当時の海洋生態系変動の詳細な検討を行った。
  • Miyata Yuma, Sawada Ken, Nakamura Hideto
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2012  GEOCHEMICAL SOCIETY OF JAPAN
     
    〕白亜紀のような古代の堆積物中には陸上高等植物に由来する有機物片が普遍的に存在している．これらは主に植物体を構成するリグニンやクチンといった抵抗性高分子から構成され，化学的に安定で微生物分解や続成作用に抵抗性を持つため選択的に保存されたものである．演者らの研究グループでは，白亜紀の陸上植物化石の化学分析により，抵抗性高分子を構成しているエステル結合態の飽和脂肪酸ユニットの組成が部位により異なることを明らかにし，化学分類指標を提案している（Ikeda et al.， submitted）．本研究では，様々な植物組織が含まれる海成堆積物中の植物由来の不溶性有機物（ケロジェン）に応用し，古植生や陸域古環境の復元に適用できるかを検討した．
  • Yamamoto Shinya, Sawada Ken, Nakamura Hideto, Kobayashi Madoka, Kawamura Kimitaka
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2012  GEOCHEMICAL SOCIETY OF JAPAN
     
    本研究では，新生代の気候変動に伴う熱帯－亜熱帯域の陸域環境変化を明らかにするために，赤道太平洋の堆積物中（IODP Sites U1331?U1338）の長鎖脂肪酸の安定炭素同位体比(δ<SUP>13</SUP>C)を測定した。その結果，陸上植物ワックスに由来する炭素数28と30の直鎖脂肪酸（C<SUB>28</SUB>， C<SUB>30</SUB>脂肪酸）のδ<SUP>13</SUP>C値は，約40～20 Maにかけて約5‰の漸移的な減少傾向を示したが，13Ma以降は一転増加に転じ，現在にかけて約10‰の増加傾向にあった。また，C<SUB>28</SUB>， C<SUB>30</SUB>脂肪酸のδ<SUP>13</SUP>C変動には，13Ma以降3回（1.6Ma， 6.5Ma， 9.5Ma）の短期的な増加イベントが認められ，南アメリカの熱帯－亜熱帯域が，中新世中期以降，複数の乾燥化イベントを繰り返しつつ，徐々に乾燥化に向かい，C4植物が増加していったことが示唆された。
  • Nakamura Hideto, Sawada Ken, Kanou Chisato, Shiraiwa Yoshihiro, Suzuki Iwane, Araie Hiroya
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2012  GEOCHEMICAL SOCIETY OF JAPAN
     
    アルケノンはハプト藻の一部の種が生産する長鎖不飽和アルキルケトンであり，生育温度に応じて不飽和度が変化する性質を利用して古水温指標として応用されてきたが，その生合成経路や生理学的な機能は未解明である。アルケノン合成種からは炭化水素である長鎖アルケンも報告され，その構造から生化学的にアルケノンと関連性の高い化合物であると考えられている。本研究ではアルケノン合成種である <I>Emiliania huxleyi， Gephylocapsa oceanica， Isochrysis galbana， Chrysotila lamellose</I> に加えて， <I>Pleurochrysis carterae</I>などのアルケノン非合成種8種のアルケノンおよび長鎖アルケン分析の結果を報告し，長鎖アルケンの先行研究をレビューしながらその地球化学的な応用の可能性を議論する。
  • Kanou Chisato, Sawada Ken, Nakamura Hideto, Shiraiwa Yoshihiro, Suzuki Iwane, Araie Hiroya
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2012  GEOCHEMICAL SOCIETY OF JAPAN
     
    ハプト藻は海洋における主要な基礎生産者であり、ほとんどの藻種は石灰質殻である円石(coccolith)を形成することが知られる。 本研究では、ハプト藻アルケノン合成種と、<Pleurochrysis carterae/>などのアルケノン非合成種8種の培養試料を用い、極性脂質画分を検出した。その結果、アルケノン合成種ではCholesterol(C<27SUB>)とBrassicasterol(C<28SUB>)が、アルケノン非合成種ではCholesterol、Brassicasterolに加えてStigmasterol(C<29SUB>)が検出され、ステロイド組成に大きな違いが見られた。また、<E. huxleyi/>， <G. oceanica/>， <I. galbana/>については同種間で生育条件の違う株によるステロイド組成の比較も行った。本講演ではハプト藻ステロイド組成の変化要因と、これらのバイオマーカーとしての適用性について考察する。
  • Ando Takuto, Sawada Ken, Okano Kazuki, Nishi Hiroshi, Takashima Reishi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2011  一般社団法人日本地球化学会
     
    中期白亜紀OAEに関する従来の研究では，海洋表層の基礎生産において，シアノバクテリアなどの特異的な生物の基礎生産における寄与について説明されてきた．一方，最近の演者らの研究によると，OAE中，必ずしもそれらの生物のみが基礎生産を担っていた訳ではないということが分かってきた．本研究では，当時の主要な基礎生産者のうち，特に渦鞭毛藻に着目し，そのバイオマーカーを用いて，OAE1aとOAE1bにおける，渦鞭毛藻の基礎生産への寄与の評価を試みた．渦鞭毛藻由来のバイオマーカーとしては，ジノステランが用いられるが，白亜系OAE試料のような続成が進んだ試料からの検出・同定が難しいため，芳香族画分でおもなピークとして検出される芳香族ジノステロイドに注目し，それらを用いた指標を検討し，各OAEにおける海洋生態系の違いを示した．
  • Nakamura Hideto, Sawada Ken, Kano Chisato, Shiraiwa Yoshihiro, Suzuki Iwane
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2011  GEOCHEMICAL SOCIETY OF JAPAN
     
    <I>Emiliania Huxleyi</I> をはじめハプト藻綱イソクリシス目に属する4種の微細藻類は炭素数37-40からなる長鎖不飽和アルキルケトン（アルケノン）を合成し，その不飽和比が生育温度に規定されるためアルケノン不飽和指数（UK37 , UK' 37）が設定され，古海洋・古気候研究において古水温指標として応用されている。アルケノン組成や水素安定同位体比を用いた塩分指標も提案されている。地球化学的指標としての応用が進む一方で，アルケノンの合成経路や生理学的機能についてはかなりの部分が未解明であり，現在，生合成経路の解明にむけた植物生理・分子生物学的研究が始まろうとしている。本講演では，アルケノンの生理学的研究のこれまでと，生合成の解明に期待される地球化学的視点について述べ，予察的成果を報告する。
  • Ikeda Kei, Sawada Ken, Takahashi Masamichi, Nakamura Hideto
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2011  GEOCHEMICAL SOCIETY OF JAPAN
     
    植物化石体や植物由来の堆積有機物の化学分類に用いられる、炭化水素やイソプレノイドなどの脂質やクチンやスベリンといった抵抗性高分子であるが、化石記録の希薄さから、続成作用を受けた地質時代の植物化石中でその化学組成がどのように保存されているのか、また保存の度合いがどういった要素・要因で異なるのかわかっていない。そこで本研究では、北海道穂別町に位置する函淵層群富内層から産出した植物化石を用い、白亜紀植物化石中の有機化合物組成について分析し、その多様性について考察した。抵抗性高分子のエステル結合態ユニットとして検出された飽和脂肪酸とn-アルカノールについて、植物部位の同定、さらには植生指標となりうるような傾向を発見した。多変量解析の結果とともに、部位や産出場所による影響と考えられる起源について考察する。
  • Sawada Ken, Nakamura Hideto, Arai Takaaki
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2010  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上高等植物の表皮や樹皮などの疎水的で硬い組織を構成する高分子量有機物は，抵抗性高分子と呼ばれる。抵抗性高分子は細胞壁や植物体に物理的強度を付与したり，微生物や昆虫の作用に対して植物体に抵抗性を与えるなどの働きをもつ。このような有機物は、植物体が堆積した後の微生物分解や続成作用に対しても抵抗性があり，古代堆積物中でもよく保存されている。演者らの研究グループでは，植物化石の抵抗性高分子の有機・生化学分析から，古植物の分類や植物生理，環境応答を復元する方法，さらに古植生あるいは生息した当時の古環境・古気候を復元する方法を開発・検討している。本講演では，これまでの研究成果をまとめて，現時点で考えられている植物化石や堆積物中の高等植物起源の抵抗性高分子の地球化学的特徴と地球科学的指標としての潜在性，さらに今後の研究の展望について紹介する。
  • Nakamura Hideto, Sawada Ken, Takahashi Masamichi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2010  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上古植生復元は化石記録に基づいて行われてきたが，中生代などの古い時代においては被子植物の出現と初期進化過程などをはじめ，未解明な部分が多く残されている。陸上植物の生体テルペノイドに由来するテルペノイドバイオマーカーは大まかに被子植物や裸子植物などの起源分類群と関連づけられるため，演者らはテルペノイドバイオマーカーを用いた古植生指標，特に被子植物植生指標を検討するため，中生代以降の被子・裸子・シダ植物化石の詳細なテルペノイド組成分析を行った。植物由来テルペノイドの続成過程は芳香族化が卓越し，芳香族化合物を用いた被子/裸子植物植生指標ar-AGIが分類群の違いをよく反映する指標として有望であることが示された。さらに，他の分類群に特有の化合物についても探索を行い報告する。
  • 中村英人, 沢田健, 高嶋礼詩
    日本古生物学会年会講演予稿集  2009/06
  • Ochiai Soichiro, Sawada Ken, Nakamura Hideto, Tsukagoshi Minoru, Akimoto Shin-ichi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2009  GEOCHEMICAL SOCIETY OF JAPAN
     
    昆虫などによって植物体に形成されるゴールの化石の化学的同定を行なうために，化石ゴールから特有のバイオマーカーや化合物の組成分布を探索した。また，化石における指標の保存を検討するため，現生のゴールも分析して比較した。試料は，中期更新統，大阪層群で産出した枝ゴール化石（被子植物のイスノキにアブラムシが形成した）と，化石とほぼ同一種の現生植物の葉，葉ゴール，枝ゴール試料である。化石ゴールの遊離態成分ではn-アルカン，バクテリア由来のホパン，被子植物バイオマーカーのオレアネンなどが検出された。化石ゴールの加水分解成分は，おもに植物の表皮に由来するクチン酸であった。化石と現生の枝ゴールのみに，2種類のクマール酸が見出された。クマール酸は，枝ゴールを同定する候補化合物となることを提示できる。また，化石ゴールの熱分解成分からは，没食子酸に類似するポリフェノール化合物を見出した。
  • Nakamura Hideto, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2009  GEOCHEMICAL SOCIETY OF JAPAN
     
    近年，堆積物や植物化石中から検出される高等植物テルペノイドバイオマーカーを用いた化学分類や古植生情報の研究が行われている．被子植物由来のオレアノイド，裸子植物（針葉樹）由来のジテルペノイドなどが典型的に知られている．演者らは白亜紀における被子植物に焦点をあてて堆積岩中の被子・裸子由来バイオマーカーを用いた植生指標を検討し，芳香族オレアノイドを用いた新指標の有用性が示唆された．しかし絶滅分類群など，化石試料を用いた基礎データが乏しい．また，白亜紀以前からのオレアナンの検出が被子植物と絶滅分類群との類縁関係を示唆するという報告もある．本公演では，絶滅分類群を含めた10種の植物化石のバイオマーカー分析の結果をまとめて，芳香族被子植物バイオマーカー指標への応用や，化学分類学的意義について議論する．
  • Nakamura Hideto, Sawada Ken, Takashima Reishi
    日本地質学会学術大会講演要旨  2008/09  The Geological Society of Japan
  • Okano Kazuki, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2008  一般社団法人日本地球化学会
     
    白亜紀には、世界中の海洋が同時期に無酸素化した海洋無酸素事変（OAE）が数回起こったと考えられている。本研究では、南東フランスのボコンチアン堆積盆におけるOAE1aおよびOAE1bの黒色頁岩試料を用いてバイオマーカー分析を行った。OAE1aではシアノバクテリア由来の2-メチルホパンが顕著に検出され、その濃度が上位に向かって増加する傾向が見られた。これは、海洋の無酸素化に伴う脱窒や嫌気的メタン酸化の活発化によってシアノバクテリアが卓越しやすい環境が形成されたことに起因する可能性が考えられる。一方OAE1bではアーキア由来のバイオマーカーであるPMIやTMIが検出された。しかし、これらのバイオマーカーはKilianより上位では高濃度で検出されるものの、それより下位の黒色頁岩層からは検出されず、一般に言われるOAE1bにおけるアーキアの卓越がKilian以降のものである可能性が考えられ、その原因については考察中である。
  • Okano Kazuki, Sawada Ken, Kotone Takuro, Nishi Hiroshi
    Annual Meeting of the Geological Society of Japan  2008  一般社団法人 日本地質学会
  • Nakatsuka Takeshi, Ohnishi Keiko, Sawada Ken, Nakamura Hideto, Tsukagoshi Minoru
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2008  GEOCHEMICAL SOCIETY OF JAPAN
     
    岐阜県多治見市の後期中新世の地層（11-10Ma）から産出した木材化石から年輪毎にセルロースを抽出し、その酸素（炭素）同位体比の経年（季節）変動を測定した。酸素同位体比の時系列を、本州中部の現生木のそれと比較したところ、同位体比の絶対値、変動範囲、変動の周期性（3？6年周期が卓越）の全てにおいて、ほぼ同じ傾向を示した。本州中部の樹木年輪セルロースの酸素同位体比は、現在、夏季の相対湿度を反映しており、その変動にはENSOの周期性が大きく影響している。それ故、今回の結果は、後期中新世においても、ENSOが本州中部の夏季水循環を支配していたこと、更に言えば、11？10Maの時点で既にENSOのダイナミクスが確立されていた可能性を、示唆するものである。
  • Nakamura Hideto, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2008  GEOCHEMICAL SOCIETY OF JAPAN
     
    陸上植物はクチンやスベリン，リグニンなどの化学的に安定で強固な抵抗性高分子をもつ．陸上植物由来の抵抗性高分子は続成過程において選択的に保存されるため古代堆積物中においてもよく保存され，巨大な炭素リザーバーである堆積物内有機物の重要なソースとなっている．また，抵抗性高分子の構成要素である単量体（モノマー）の組成は起源となる植物の分類群により異なることが知られていて，起源植物の分類学的情報を与える指標としての応用が考えられるが，化石について検討された例はほとんどない．本研究では化石中における有機物の保存の状態や抵抗性高分子の分類群による差異の有無などを確かめるため，有機物を豊富に含む炭質の植物化石を用いて加水分解により得られるエステル結合態成分を分析した．本講演では，植物化石の抵抗性高分子を用いた化学分類や続成変化の検討について報告する．
  • Okano Kazuki, Sawada Ken, Takashima Reishi, Nishi Hiroshi
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2006  GEOCHEMICAL SOCIETY OF JAPAN
     
    海洋無酸素事変 (OAE) は海洋中に無酸素環境が広がる全球的なイベントであり、海洋の生態系に大きな被害を与え
  • Nakamura Hideto, Sawada Ken
    Abstracts of Annual Meeting of the Geochemical Society of Japan  2006  GEOCHEMICAL SOCIETY OF JAPAN
     
    中生代のような古代堆積物中において，陸上高等植物に由来する有機物片が普遍的に含まれている。それらは植物体の抵抗性（難分解性）高分子から由来し，生体情報を比較的よく保存している。また，高等植物に由来する低分子量分子，いわゆるバイオマーカーも構造が一部変化しているが同定される。本研究では，北海道大夕張地域に分布する下部白亜系（Albian）蝦夷層群に含まれる植物片化石を用いて，化石中の抵抗性高分子を加水分解し，得られた有機化合物の組成分布を解析した。また，同試料に含まれる遊離態成分のバイオマーカー分析も行った。バイオマーカーとして，裸子植物がもつジテルペノイド由来の炭化水素がおもに検出された。抵抗性高分子やバイオマーカーの分析から，白亜紀前期における被子/裸子植物比などの古植物相の復元について検討した。
  • Examination of depositional environment of turbidites in the middle Miocene Kawabata Formation based on the compositions of kerogen and biomarker
    Okano Kazuki, Sawada Ken
    Annual Meeting of the Geological Society of Japan  2005  The Geological Society of Japan
  • SHINMURA Tatsuya, SAWADA Ken, SUZUKI Noriyuki, SHIBA Masahiro
    Annual Meeting of the Geological Society of Japan  2003  The Geological Society of Japan
  • Marine environmental change revealed from the long-chain alkenone analysis in the late Quaternary sediments of the northwest North Pacific off Japan  [Not invited]
    沢田 健, 半田 暢彦
    日本地球化学会1995年会  1995/11
  • SAWADA Ken, HANDA Nobuhiko
    Annual Meeting of the Geological Society of Japan  1995  The Geological Society of Japan
  • SAWADA Ken, HANDA Nobuhiko
    Annual Meeting of the Geological Society of Japan  1994  The Geological Society of Japan
  • Density separation of macerals from various kerogens and their carbon isotope composition : An example of the Takafu district in the northern Fossa Magna region  [Not invited]
    沢田 健, 秋山 雅彦
    日本地質学会学術大会講演要旨 1993年 一般社団法人 日本地質学会  1993/04

Association Memberships

  • JAPAN GEOSCIENCE UNION   American Geophysical Union   日本有機地球化学会   日本地質学会   日本地球化学会   European Association of Organic Geochemists   日本古生物学会   The Japanese Association of Organic Geochemists   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/04 -2026/03 
    Author : 沢田 健, 桑田 晃, 力石 嘉人, 入野 智久, 加藤 悠爾
     
    本研究では、深海掘削および陸上調査によって得られた新第三紀堆積物から、藻類および陸上植物の分子化石（バイオマーカー）、藻類微化石、生物源シリカを分析し、新生代の北太平洋におけるグローバルな海洋ー陸域間の生物地球化学的循環と生態系の連鎖（リンケージ）、環境気候システムとの関連性を解明する。海洋・陸域生態系が駆動する長時間スケールの物質循環システムの解明という観点から、海洋基礎生産と陸源有機物の海洋への輸送量の変動の体系的で定量性の高い復元を目指す。さらに、新しい古環境復元法を確立するため、新規の藻類バイオマーカーの探索とその解析法、陸上植物バイオマーカーの分子内同位体比解析法を開発する。2022年度における主な研究成果は次のとおりである。 1. 北部北太平洋アラスカ湾掘削コア（U1417）のバイオマーカー分析を行い、珪藻、ハプト藻、渦鞭毛藻、真正眼点藻などに由来するバイオマーカーを検出し、低分解能で大まかではあるが過去1000万年間の海洋基礎生産変動を復元した。また、ハプト藻由来の長鎖アルケノンおよび真正眼点藻由来の長鎖アルキルジオールを用いた古水温計によって海洋表層水温の変動を復元した。これらの水温の変動パターンは概ねよく一致し、全体的には中新世以降の全球的な寒冷化傾向を示すことがわかった。 2. 北海道中南部の日高町などに分布する中新統荷菜層における泥質堆積岩から、陸上セクションからは極稀な長鎖アルケノンが検出されることを発見した。そのアルケノン古水温計を用いて中期～後期中新世における体系的な海洋表層水温と海洋基礎生産の変動を復元した。 3. 陸源有機物において陸上植物だけでなく菌類のような生物のバイオマーカーにも着目し、特に地衣類の生体試料を用いて、新規のバイオマーカーを検討した。その結果、ファルネンなどのテルペノイドがそのバイオマーカーになり得ることを明らかにした。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/04 -2026/03 
    Author : 沢田 健, 桑田 晃, 力石 嘉人, 入野 智久, 加藤 悠爾
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2021/04 -2025/03 
    Author : 高嶋 礼詩, 黒田 潤一郎, 西 弘嗣, 沢田 健, 林 圭一, 折橋 裕二, 星 博幸
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2020/04 -2024/03 
    Author : 西 弘嗣, 高嶋 礼詩, 沢田 健, 柴田 正輝
     
    本年度は下部白亜系に焦点をあて、蝦夷層群以外にも野外調査と試料の採集を実施した。下部白亜系下部では、福島県南相馬市に露出する相馬中村層群と宮城県気仙沼市大島の大島層群で柱状図の作成と泥岩、凝灰岩試料の採集を実施した。有機炭素の炭素同位体比を測定した結果、両地層からLate Valanginian Event層準を特徴づける炭素同位体比曲線のピークを両層群から見出すことができた。北海道の蝦夷層群下部の惣芦別川層～シューパロ川層でもルートマップの作製および泥岩・凝灰岩試料の採集を実施した。泥岩試料については高解像度での採集を行い、炭素同位体比の測定を実施している。凝灰岩試料については、放射年代の測定を行い、下部白亜系の年代モデルを構築が可能となった。 有機地球科学分析では、比較研究のため米国のGreat Valley Sequence (GVS)のOAE2時の地層で陸上植物に由来する芳香族テルペノイドを用いた古植生解析を行った。被子/裸子植生比は、OAE層準では1st build-upなどにおいて一時的に減少傾向を示すものの、OAE層準を通して徐々に増大し回復期以降で減少することが明らかとなった。さらに、蝦夷層群佐久層から菌類バイオマーカーの探索と群集組成を評価する指標の開発を行った。羽幌川層では陸源ケロジェン・花粉分析を行い、被子植物花粉/裸子植物花粉個数比を明らかにした。恐竜化石では、植物食恐竜の中で特殊化した摂食方法を獲得した鳥脚類に注目し、この時期に生じた温暖化による植物相変化との関連性を考察した。アプチアン期以前、イグアノドンに代表される原始的なグループは、欧州や北米に生息していたが、アジア地域ではオーテリビアン期の立川層以外では知られていない。アプチアン期からアルビアン期になると、ハドロサウルス上科がアジアで多様化した。しかし、手取層群北谷層では、進化的な種と原始的な種が共存していたことがわかった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2017/04 -2020/03 
    Author : Kuwata Akira
     
    Diatom is the most diversified and successful microalgal group in modern oceans, fixing about the same amount of carbon dioxide as tropical rainforests. Parmales is a silicified pico-phytoplankton group. Recent our success of isolation of Parmales from the Oyashio water in the Western Subarctic Pacific and characterizing of these isolated strains revealed that Parmales belong to Heterokonta and share a common ancestor with diatoms and may play a key role in understanding their origin and evolutionary success. We have studied on Parmales using ecological, physiological, genomic and biogeochemical approaches and analyzed their genomes, silica cell wall formation process, life cycle and specific biomarkers (molecular fossils) and compared biological characters between Parmales and diatoms.
  • 文部科学省：科学研究費補助金(基盤研究(B))
    Date (from‐to) : 2018 -2020 
    Author : 沢田 健
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2018/03 
    Author : Kuwata Akira, KAWACHI Masanobu
     
    Parmales are an unknown small marine phytoplankton group with a silicified cell wa ll. Based on similarities in cell wall structure, Parmales has been proposed as a close relative of diatom s, the most successful microalgal group in modern oceans, and may play a key role in understanding their o rigin of silica cell wall and early evolution, which have not yet been clearly established. Recently, we i solated the first ever culture of Parmales in the Oyashio region of Japan. Molecular phylogenetic analysis of this culture indicated that Parmales was within the bolidophycean clade of autotrophic naked flagellates and a sister group of diatoms. We have studied on Parmales using ecological, physiological, genomic and biogeochemical approaches and analyzed their silica cell wall formation and mitosis process, global oceanic distribution , life cycle, genome , life cycle and specific biomarkers (molecular fossils).
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/04 -2017/03 
    Author : Suto Itsuki
     
    This study has demonstrated the linkage among the development of North American ice sheet, the erosion history on land, and the changes of microfossils during the last one million years using continuous sediment materials from the Gulf of Alaska (IODP Sites U1417, U1418 and U1419). Common presence of planktic foraminifers in subject cores permits to establish the orbital-scale oxygen isotope stratigraphy during last 1.0 million years ago in the Gulf of Alaska. The climate-ice sheet interactions were also investigated using a number of proxies including the diatom and radiolarian assemblages, the geochemical characteristics, and the physical properties of the sediments.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014 -2016 
    Author : Sawada Ken, IGARASHI Yaeko
     
    The objective of this study is to reconstruct variations in paleovegetation and terrestrial paleoenvironment by analyses of terrestrial plant-derived biomarkers and pollen/spore in sediment cores from northeastern Atlantic Ocean off the Iberian Peninsula (U1385) and the Japan Sea off the southwestern coast of Hokkaido (U1423) collected by the International Ocean Drilling Program (IODP). We reconstructed the paleovegetation variations during 4.3 million years and centurial-scale variations during the marine isotope stages (MIS) 12 - 10 in U1423 and U1385 sites, respectively. In particular, the paleovegetation variations reconstructed by the indicators for diterpenoids derived from Taxodiaceae/Cupressaceae and Pinaceae are synchronous to the global climatic variations such as warm/cool conditions with glacial/interglacial or centurial scales, confirming high applicability of the terpenoid proxy for reconstructing paleovegetation from deep sea sediment.
  • 海洋ハプト藻類のアルケノン合成経路の解明と基盤技術の開発
    JST：CREST
    Date (from‐to) : 2010 -2015 
    Author : 白岩善博
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2012 -2014 
    Author : TAKAHASHI Masamichi, HISADA Ken-ichiro, SAWADA Ken
     
    The purpose of research purpose is to recover Early Cretaceous age fossil plants from Mongolia. The focus is on mesofossils, small dispersed fossil flowers, fruits, cones, and seeds. Mesofossils are new type of plant fossils that have well preserved three dimensional structure. We have performed field trips in Tevshiin Govi, Tugrug, Shivee-Ovoo and Shine Khudag localities during 2012-2013.The fossiliferous layers belong to the Tevshiin Govi Formation, a sequence of conglomerates, sandstones, and siltstones, as well as thick coal and lignite seams, that were deposited in a terrestrial and fluvio-lacustrine system. They also contain a varied assemblage of plant remains, including copious leaves, stems, wood, roots, and reproductive structures such as cones, seeds, cupules. The goal of the research is to document seed plant diversity in central Mongolia during the Early Cretaceous.
  • 未知の藻類：パルマ藻が解き明かす海洋を支える珪藻の進化
    一般財団法人 キャノン財団：キャノン財団研究助成金
    Date (from‐to) : 2011 -2014 
    Author : 桑田 晃
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2013 
    Author : HASEGAWA Takashi, SAWADA Ken
     
    Cretaceous Cenomanian/Turonian boundary is known as a period of Oceanic Anoxic Event 2 (OAE2). During OAE2, large amount of organic matter deposited over extended sea bottom of the global oceans, and considerable climatic change associated with the disturbance of carbon cycles are under debate. From the Yezo Group in Hokkaido, stratigraphic studies with exclusively high resolution suggested that strong environmental perturbation happened within duration of twenty thousand years. We focused on that event (NSP) and studied biomarkers (organic molecular fossils), especially compound-specific carbon isotope values on biomarkers derived from terrestrial higher plants. Our results showed short term climatic change prevailed just before NSP over terrestrial East Asia during OAE2 interval.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2013 
    Author : KUWATA Akira, SATO Naoki, SAIYO Kenji, YOSHIKAWA Shinya, SAWADA Ken, ICHINOMIYA Mutsuo, KAWACHI Masanobu, OHKI Kaori, NAKAMURA Youji
     
    Parmales are an unknown small marine phytoplankton group with a silicified cell wall. Based on similarities in cell wall structure, Parmales has been proposed as a close relative of diatoms, the most successful microalgal group in modern oceans, and may play a key role in understanding their origin of silica cell wall and early evolution, which have not yet been clearly established. Recently, we isolated the first ever culture of Parmales in the Oyashio region of Japan. Molecular phylogenetic analysis of this culture indicated that Parmales was within the bolidophycean clade of autotrophic naked flagellates and a sister group of diatoms. We have studied on Parmales using ecological, physiological, genomic and biogeochemical approaches and analyzed their phylogenetic relationship between Bolidophycea and diatoms, chloroplast and mitochondria genomes, silica cell wall formation process, population dynamics in the Oyashio region, life cycle and specific biomarkers (molecular fossils).
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2013 
    Author : SAWADA Ken, TAKASHIMA Reishi
     
    The objective of this study is to reconstruct long time scale variations in paleovegetation and terrestrial paleoenvironment by analyses of terrestrial plant-derived biomarkers and kerogens in sedimentary rocks from the Cretaceous Yezo Group, Hokkaido, Japan. In particular, we found rapid changes in angiosperm / gymnosperm vegetation ratio and coniferous vegetation evaluated by analysis of terrestrial plant terpenoid biomarkers. Moreover, we suggest that composition of long chain n-alkanols released from resistant macromolecule in kerogen can be useful as an indicator of deciduous broad leaf plant vegetation. Variation in the paleovegetation using the long chain n-alkanols released from kerogen is almost synchronous to that in angiosperm / gymnosperm vegetation using terrestrial plant biomarkers, confirming high applicability of the released n-alkanol proxy for reconstructing paleovegetation from ancient sediment.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2010 -2012 
    Author : Hiroshi NISHI, 高嶋 礼詩, Ken SAWADA, Hodaka KAWAHATA, Reishi TAKASHIMA
     
    Expansion of anoxic environments and extinction of marine biota occurred in the Tethys Sea and the Atlantic Ocean during the earliest Albian period, mid-Cretaceous (113 million years ago). In order to understand the trigger and mechanism of this event, we analyzed microfossil assemblages, organic and inorganic geochemistry and clay mineralogy of the black shale which were deposited during this event. Our analyses demonstrate that the expansions of anoxic environment were triggered by increased continental run-off which was caused by extremely humid climate in response to the mid-Cretaceous global warming. Increased run-off may have caused surface ocean eutrophication and elevation of primary productivity, and resulted in expansion of anoxia.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(C))
    Date (from‐to) : 2009 -2011 
    Author : Hiroshi NISHI, 沢田 健, 高嶋 礼詩, Reishi TAKASHIMA, Ken SAWADA
     
    I established detailed biostratigraphy of planktonic foraminifera and dinoflagerata systs in the Aptian-Maastrichtian sequence of the Yezo and Nemuro Groups exposed in Hokkaido, Japan. Based on above biostratigraphic correlations, I integrated carbon and strontium isotope stratigraphy and 12 U-Pb and 40Ar/39Ar radiometric dating of tuff beds This integrated stratigraphy has enabled to high resolution international stratigraphic correlations.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(C))
    Date (from‐to) : 2008 -2010 
    Author : Ken SAWADA
     
    A research representative developed analytical methods by using isoprenoid quinones and the related compounds in sediment for reconstructing variations in productivity and assemblages of microorganisms in past time. From the results, it was suggested that free and kerogen-bound tocopherols, in which structure are resemble to isoprenoid quinones, could be useful as marine algal biomarker in present and ancient (the Neogene and Cretaceous) sediments, respectively. Phylloquinone bound in kerogen might be derived from cyanobacteria and can be useful as an indicator of its productivity in limited geological samples. In addition, it was pointed out that free sedimentary aromatic quinone, which is thought to be a lichen biomarker, have a potential for reconstructing its productivity and input/sedimentation in marine environment.
  • Fundamental study on algal lipid with reference to application to bio-oil resource
    JST Basic Research Programs (Core Research for Evolutional Science and Technology :CREST)
    Date (from‐to) : 2010
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : SUZUKI Noriyuki, SAWADA Ken, WATANABE Tsuyoshi
     
    高等植物バイオマーカーの安定水素同位体比と菌類バイオマーカーの存在度に注目して地質時代における陸域の水循環を評価する方法を提案した. 新生代始新世・漸新世の一連の堆積岩に適用した結果,同時期の中緯度陸域は著しく多雨湿潤であり,顕著な基礎生産と炭素固定が行われていたと考えられる. 新生代始新世から現在までの長期的な地球気温の低下は草本質植物の進化拡大や大陸基礎生産による生物フォーシングが重要な役割を果たしたと考えられる.
  • 文部科学省：科学研究費補助金(若手研究(A))
    Date (from‐to) : 2006 -2007 
    Author : 沢田 健
     
    白亜紀の陸域における気候変動と陸域生態系の進化,特に被子植物の進化・拡散とその影響による陸域生態系の変化を復元することを目的として,北海道などの白亜系堆積岩や大型植物化石を対象として古生物学・生物地球化学の研究を進めた。本研究は,古代植物に由来するバイオマーカーと抵抗性高分子に着目して、それらを用いて古生態・古気候記録を解読することが特徴である。研究の進め方として,(1)北海道白亜系の陸城古気候変動の復元と,(2)古代植物のバイオマーカー・抵抗性高分子の分析方法の開発等の基礎研究の2つのアプローチから行なった。平成19年度の研究成果は以下のとおりである。1.北海道中央部の大夕張,三笠,苫前地域に分布する地層から堆積岩および植物化石片を採集した。採集層準は,空知層群最上部(Aptian)から蝦夷層群佐久層上部(Turonian)にわたり,それらを試料としてバイオマーカー分析を行った。測定には,本科研費で設置されたガスクロマトグラフ質量分析計(GC/MS)を用いた。その結果,Aptian層準から被子植物バイオマーカーを検出した。これは日本では最古の被子植物の記録となる。また,Aptian〜Turonianにおける北海道の被子/裸子植物比などの陸上古植生の変動を復元した。2.北海道などの白亜紀から古第三紀(北大博物館収蔵)の葉・材化石を用いて,植物化石の抵抗性高分子の基礎研究を行った。化石を加水分解して得られた化学部位(分子ユニット)をGC/MS測定から同定・定量し,その組成分布を調べた。それらの結果から,植物化石の化学分類や化石の保存度の評価などへの適用性について検討した。
  • 文部科学省：科学研究費補助金(若手研究(B))
    Date (from‐to) : 2004 -2005 
    Author : 沢田 健
     
    白亜紀における植物の進化とそれによる陸域環境の変化を復元することを目的として,北海道白亜系の堆積岩および天型植物化石を対象に古生物学・生物地球化学的研究を進めた.本研究は、丁古代植物に由来する化石ポリマーに着目して,それから古生態・古環境記録を解読することが特徴であり,研究の進め方も,(1)北海道白亜系の陸域古環境変動の復元と,(2)古代植物の化石ポリマー分析方法の開発等の基礎研究,の2つのアプローチから行なっている.平成17年度に行なった研究およびその成果は以下のとおりである.1.北海道大夕張地域に分布する蝦夷累層群シューパロー川層(白亜紀前期Albian相当)の地質調査と露頭の地層からの砂岩,泥岩および大型植物化石を採集した.2.本科研費で平成16年度に設置された蛍光顕微解析装置で,堆積岩中から分離した植物化石に由来する有機物破片を蛍光特性から分類した.また,砂岩試料から植物由来有機物破片を効率的に分離する遠心比重分離法を開発・検討した.3.比較的大型の木片化石をアルカリ加水分解することによって,エステル結合した化石ポリマーを分離した.その化石ポリマーを分析し,クチンやリグニンを構成するポリマーに由来する分子ユニットを数種類同定した.特に,クチンポリマーの脂肪酸分子ユニットの炭素数分布情報が,植物化右の化学分類に適用できることがわかった.また,テルペノイドのようなバイオマーカーも遊離態成分として同定され,化学分類や古環境復元に使えることを確認した.4.砂岩中に含まれる植物片を遠心比重分離してすべて回収した.その試料のバイオマーカー分析の結果,北海道の白亜系Albianに堆積した陸上植物は,裸子植物が優占的で被子植物は含まれないことが判明した.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2003 -2005 
    Author : Hisatake OKADA, 鈴木 徳行, 北里 洋, Hodaka KAWAHATA, Hiroshi NISHI, Naohiko OHKOUCHI, Ken SAWADA, Tatsuhiko SAKAMOTO
     
    This research group (Leader : Hisatake Okada) had started in 1999 a field survey and sampling project in Southern France using the Grant-in Aid for Scientific Research (No. 11691113). The project was designed as a precursory study for one of IODP (Integrated Ocean Drilling Program)'s main target, the "Paleoenvironment under Extreme Climates". The team had studied extensively the OAE1b interval of Mid-Cretaceous Warm Event, and had obtained a massive columnar section containing Paquier interval, and also had conducted several test drilling at the upper level of OAE1b interval.In this new research project (Grant-in Aid for Scientific Research No. 15253007) designed as the second project to study the paleoceanography of Mid-Cretaceous OAE sequence in Southern France, we have planed to obtain high quality cores from OAE1a and OAE 1b intervals. We have hired a professional company FORACO for this task and have succeeded to recover a 60m core from Goguel (OAE1a) level at 10km north of Barrem Village and also 15m cores from Killian (OAE1b) level at St.Andre. These were the first cores ever recovered from these intervals. In order to conduct high-quality analysis for these cores, we have developed new techniques : a technique to fix the whole core by a special type of resin without any disturbance of the fractured portions and a technique of precise micro drilling to obtain samples at one mm intervals.In addition to elaborate non-destructive analysis for the whole cores, various micropaleontological, geochemical and sedimentological analysis has been conducted. As a result of these analysis it is now clear that two types of oceanic conditions existed during the formation of black shales in the OAE1a event : a condition with total water column becoming anoxic resulting a devastation to marine bioshere, and the other in which anoxic water did not reached to photic zone causing a limited effect to marine biota. It is also evident that during the Killian level of OAE1b event four cycles of anoxic fluctuations occurred. The cause of this fluctuations can be deduced to fluctuation of primary production level resulted by changing amount of terrestrial nutrient supply.
  • Molecular paleontology and paleobiology of resistant macromolecule in plant fossil
    Date (from‐to) : 2003
  • 自然界に存在する巨大分子の地球化学的研究
    北海道大学理学研究科：理学未来潮流グラント
    Date (from‐to) : 2001/11 -2002/03 
    Author : 沢田 健
  • Biogeochemical studies on terrestrial ecosystem evolution, with respect to its effect in earth's environment
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 2000
  • Biogeochemical studies on geomacromolecule in sediment and fossil
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 2000
  • Paleoenvironmental and paleoclimatological reconstructions by biomarkers in sediment and fossil.
    Date (from‐to) : 1996

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