Fossil diatom assemblages for the past 280,000 years from the BIW08-B core in Lake Biwa, Japan

• Nagayasu Koichi

  Department of Mountain and Environmental Sciences, Interdisciplinary Graduate School of Science and Technology, Shinshu University

• Kumon Fujio

  Department of Environmental Sciences, Faculty of Science, Shinshu University

• Takemura Keiji

  Institute for Geothermal Sciences, Graduate School of Science, Kyoto University

Bibliographic Information

Other Title

• 琵琶湖堆積物コアBIW08-Bにおける過去28万年間の珪藻化石群集変動
• ビワコ タイセキブツ コア BIW08-B ニ オケル カコ 28マンネンカン ノ ケイソウ カセキ グンシュウ ヘンドウ

Abstract

The authors have performed diatom analysis at 50- cm intervals (ca. 1,500-year intervals) for the BIW08-B core taken from Lake Biwa in 2008. The core is 100.30m long, and is composed mainly of homogenous silty clay except for its basal part where sandy sediments are dominant. Based on the relationship between their known ages and the depths of widespread marker tephra beds identified in the core, depth of sediment can be converted into sedimentation age. Sedimentation rate was calculated to be as much as 30-40cm/ka.<BR>The following 7 diatom assemblages have been identified in the core. Zone 1 : 〜99.51m (〜276ka) ; diatom composition is similar to the present assemblage characterized by dominant Stephanodiscus suzukii. Zone 2 : 99.51-65.01m (276-203ka) ; diatoms are scarce in number, and benthonic diatoms such as Achnanthes spp., Opephora spp. and Staurosila spp. are relatively abundant. Zone 3: 65.01-61.02m (203-192ka); Aulacoseira nipponica is predominant. Zone 4: 61.02-47.02m (192-153ka) ; diatom test number is decreased and Stephanodiscus sp. becomes predominant instead of Aul. nipponica. Zone 5 : 47.02-28.41m (153-100ka) ; diatoms become slightly abundant and S. suzukii is predominant. Zone 6 : 28.41-21.01m (100-74ka) ; diatom abundance is subtly decreased, Aul. nipponica becomes dominant, and S. suzukii is decreased. Zone 7 : 21.01-0.21m (74-0.6ka) ; both S. suzukii and Aul. nipponica are dominant and abundance varies quasiperiodially.<BR>The diatom assemblage for 276 to 203ka seems to correspond with a delta advance from the Echi River. The successive changes in diatom assemblages of the BIW08-B core since 203ka as clarified here are very similar to those of the Takashima-oki core, and represent temporal diatom changes in the offshore areas throughout Lake Biwa. These changes in diatoms might be controlled by precipitation associated with the East Asian summer monsoon.

Journal

• The Quaternary Research (Daiyonki-Kenkyu)

  The Quaternary Research (Daiyonki-Kenkyu) 53 (6), 297-309, 2014

  Japan Association for Quaternary Research

Keywords

• late Quaternary
• Lake Biwa
• BIW08-B core
• diatom analysis
• Echi River
• East Asian monsoon

Details

• CRID: 1390001206497630592
• NII Article ID: 130005088895
• NII Book ID: AN0034136X
• DOI: 10.4116/jaqua.53.279
• ISSN: 18818129
• ISSN: 04182642
• NDL BIB ID: 025950449
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I025950449
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed