Environmental Change in Coastal Lowlands around the Lake Hamana during the Middle to Late Holocene

• Yoshiki SATO

  Graduate Student, Kyushu University

• Osamu FUJIWARA

  Active Fault and Earthquake Research Center, National Institute of Advanced Industrial Science and Technology

• Eisuke ONO

  Faculty of Education, Niigata University

• Masatomo UMITSU

  Department of Geography, Nara University

Bibliographic Information

Other Title

• 浜名湖沿岸の沖積低地における完新世中期以降の環境変化
• ハマナコ エンガン ノ チュウセキ テイチ ニ オケル カンシンセイ チュウキ イコウ ノ カンキョウ ヘンカ

Abstract

Analyses of the sediment cores around the Lake Hamana, a coastal lake along the Pacific coast of central Japan, indicated stepwise environmental change from a shallow marine (intertidal zone of a bay) to a freshwater pond or marsh, which occurred during the middle to late Holocene. We carried out an array coring survey using a handy geoslicer and hand corer in two lowlands, the Rokken-gawa lowland and the Miyakodagawa lowland. Drilling cores collected by the local government and private companies were also analyzed. The depositional environment of the cored section was estimated from the depositional facies with the help of diatom and molluscan assemblages and electric conductivity. The timing of the environmental changes was estimated from 16 radiocarbon ages determined using the AMS method. The following three steps of environmental change were recognized in both lowlands: 1) 5,000–6,000 to 3,800 calBP, gradual environmental change from a muddy intertidal zone or shallow bay to a brackish lagoon or freshwater marsh; 2) 3,500–3,800 calBP, temporal expansion of the seawater invasion into the Lake Hamana resulting in the formation of a brackish marsh; and 3) 3,400–3,500 calBP, rapid environmental change from the brackish marsh to a freshwater pond or marsh. The environmental change in the lowlands around 3,400–3,500 calBP was synchronous with the environmental change from brackish to fresh water in central Lake Hamana, which was reconstructed from the analyses of sediment cores in a previous study. We infer that the environmental change reflects a rapid decrease in seawater invasion into the Lake Hamana, which was related to the development of sandbars sheltering the Lake Hamana from the Pacific Ocean.

Journal

• Geographical review of Japan series A

  Geographical review of Japan series A 84 (3), 258-273, 2011

  The Association of Japanese Geographers

Keywords

• environmental change
• diatom assemblage
• electric conductivity
• the Lake Hamana
• Holocene

Details

• CRID: 1390001205300714752
• NII Article ID: 10029579762
• NII Book ID: AA11591990
• DOI: 10.4157/grj.84.258
• ISSN: 21851751
• ISSN: 18834388
• NDL BIB ID: 11115548
• Web Site: http://id.ndl.go.jp/bib/11115548
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I11115548
• Web Site: https://www.jstage.jst.go.jp/article/grj/84/3/84_258/_pdf
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed