D'Hondt, S.

Horikoshi, K.

Inagaki, F.

Jørgensen, B.

Nealson, K.

Suzuki, M.

English

MPG.PuRe

Goldschmidt Conference Abstracts 2003 A171Cosmogenic 10Be production duringlow sea-level periods of ice ages inunderwater rocks from theTugaru Strait, JapanM. IMAMURA 1, K. J. KIM2,3 AND R. FINKEL41National Museum of Japanese History, Sakura, Chiba285-8502, Japan, imamura@rekihaku.ac.jp2Institute of Geological and Nuclear Sciences, Ltd., LowerHutt, New Zealand, Present: 3Institute of Meteoritics,University of New Mexico, Albuquerque, NM,87131,USA, kkim@unm.edu4Center for Accelerator Mass Spectrometry, LawrenceLivermore National Laboratory, Livermore, CA 94550,USA, finkel1@llnl.govIntroductionThe formation of land bridge during ice age is one of thekey issues in understanding post-glacial movement of humanbeing in the world. The land bridges between Japan and theEurasian continent including Korea and Far East Russia areimportant in studying the migration of people in the Japaneseislands, and of origination and spread of Paleolithic andNeolithic culture in East Asia. Our preliminary study isdesigned to determine the feasibility of using cosmogenicnuclides as a dating tool in the investigation of land bridgesbetween the continent and Japan during the past glacial ages.ResultsCosmogenic nuclide production of 10Be and 26Al wasinvestigated using underwater rock samples obtained from theTsugaru Strait between Honshu (Aomori) and Hokkaido(Hakodate), the two main islands of Japan. Sedimentary rocksamples from depth (water + rock) range between 3,760 g cm-2and 6,140 g cm- 2 were obtained. The 10Be concentrationsobtained from this depth range were determined to be from 8 x104 and 8 x 103 atoms/g SiO2. The 10Be results are muchgreater than those of the steady state underground productionat the relevant depths, indicating the effect of pre-exposure byneutron spallation during the past glacial period. Especially, asample having a shallow rock dpeth, not the current waterdepth, indicated relatively high 10Be concentration. Thisconfirms that pre-exposure by neutron spallation with respectto sea level change can be detected by measuring cosmogenicnuclide concentration from underwater rocks.  The measured10Be data were simulated using a model calculation, which hasbeen developed by parameters of sea level change, uplift rate,and erosion rate of this study. This model could be an essentialtool in understanding cosmogenic nuclide productionunderwater for exposure dating applications.ConclusionsThe data of our preliminary study confirm that theinvestigation of land bridges of the world can be feasible usingunderwater production of cosmogenic nuclides, and this studywill provide new guidance in further investigation of landbridge studies using cosmogenic nuclides.Acknowledgement: This study was supported in part by JSPSGrant-in-Aid (#12874064).Subseafloor microbial diversity in thePeru Margin (ODP Leg. 201)FUMIO INAGAKI 1, MASAE SUZUKI1, KENNETH H.NEALSON1,2, KOKI HORIKOSHI1, STEVEN L. D’HONDT3,BO B. JØRGENSEN4, AND ODP LEG. 201 SHIPBOARDSCIENTIFIC PARTY1Subground Animalcule Retrieval (SUGAR) Project, FrontierResearch System for Extremophiles, Japan MarineScience & Technology Center, Yokosuka, Japan(inagaki@jamstec.go.jp)2Department of Earth Sciences, University of SouthCalifornia, Los Angeles, USA (knealson@usc.edu)3Graduate School of Oceanography, University of RhodeIsland, Narragansett, USA (dhondt@gso.uri.edu)4Department of Biogeochemistry, Max-Planck-Institute ofMarine Microbiology, Bremen, Germany (bjoergen@mpi-bremen.de)The subseafloor environment has been proposed to be thelargest biosphere on Earth, as based on estimates of cells inmarine sediment cores recovered by the Ocean DrillingProgram (ODP). However, it is not well-known what kinds ofmicroorganisms are present, how do their distributions relatewith geological settings, and how do their metabolic activitiesimpact the global geochemical cycles. The ODP Leg. 201 tookplace in the eastern equatorial Pacific and Peru coastal marginin 2002, and was the first expedition in ODP history targetedmainly on microbiology and biogeochemistry in thesubseafloor biosphere.In this presentation, we show the vertical profile data ofthe results from culture-independent molecular ecologicalsurveys in ODP sediment core columns collected from the twodrilling sites, 1227 and 1230, located on the land slope of theaccretionary wedge in the Peru Trench. The sediment coresrecovered from Site 1230 contained high organic carbon andmethane, whereas those from Site 1227 contained lowconcentrations of these chemical components. Bulkprokaryotic nucleic acids were extacted and purified fromeach sediment, and 16S rRNA genes (rDNA) were amplifiedby PCR using domain specific primers. The analyses of rDNAsequences of clone libraries, quantitative-PCR for archaealand bacterial rDNA, and T-RFLP fingerprint analysis revealedthe previously unknown vertical distribution and diversity ofArchaea and Bacteria in two geologically discrete subseafloorenvironments. On the basis of the results from molecularmicrobiology and biogeochemistry of ODP Leg. 201, theecological significance of subseafloor microbial life will bediscussed.

Subseafloor microbial diversity in the Peru Margin (ODP Leg. 201)

http://hdl.handle.net/21.11116/0000-0007-9397-8

Subseafloor microbial diversity in the Peru Margin (ODP Leg. 201)

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