georefid:2004-047317SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=2004-047317<gco:CharacterString>Diatom biostratigraphy of the middle Miocene marine sequence of the Ayukawa section in the Fujioka area, Gunma Prefecture, central Japan, with special reference to the correlation between the diatom biohorizon D55 and an (super 40) Ar- (super 39) Ar age</gco:CharacterString>2002-01-01publicationgeorefid:2004-047317Suto, ItsukiUniversity of Tsukuba, Institute of Geoscience, Ibaraki, JapanauthorTakahashi, MasakiGeological Survey of Japan, JapanauthorYanagisawa, YukioauthorNippon Chishitsugaku Gakkai, Tokyo, JapanpublisherdocumentHardcopyChishitsugaku Zasshi = Journal of the Geological Society of Japan108 (11)746-760Marine diatoms were examined for the 245 meter-thick Middle Miocene sequence (the Haraichi and Itahana Formations) exposed along the Ayukawa River in the Fujioka area. Gunma Prefecture, central Japan. The sequence is correlative with the Denticulopsis praedimorpha Zone (NPD 5B) and the Thalassiosira yabei Zone (NPD 5C) of Yanagisawa and Akiba (1998). The last common occurrence (LCO) of D. praedimorpha (D55), a biohorizon which defines the NPD 5B/5C boundary, is recognized between 1 and 3 meters above the Baba Tuff Bed in the upper Haraichi Formation. The numerical age of the biohorizon D55 can be regarded as same as the (super 40) Ar- (super 39) Ar age of the Baba Tuff Bed (11.28+ or -0.08 Ma), because of a high accumulation rate (ca. 35-39 cm/1,000 yr.). This age is about 0.2 Ma younger than the magnetostratigraphically estimated age for D55 at ODP Site 887 and 884 in the high latitude North Pacific. The direct relationship between the D55 biohorizon with high-resolution radiometric age should give important constraints on refining a global geologic time scale for the Miocene interval.completedStratigraphyalgaeAr/ArAsiaAyukawa JapanBaba TuffCenozoiccentral JapancorrelationDenticulopsisdiatomsFar EastFujioka JapanGumma JapanHaraichi FormationHonshuJapanKoizumiaLeg 145microfossilsmiddle MioceneMioceneNeogeneNitzschiaOcean Drilling ProgramODP Site 887Plantaesequence stratigraphyTertiaryThalassiosiraTomioka Groupurn:org.iodp:exp:145urnlargerWorkCitationcampaignurn:org.iodp:exp:145:site:887urnlargerWorkCitationstudyurn:org.iodp:exp:145urnlargerWorkCitationcampaignJapanesegeoscientificInformation139.0200139.030035.000035.1000