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Holocene sedimentary history of some coastal plains in Hokkaido, Japan V. Sedimentary history of Kushu Lake and Akkeshi
Author(s) -
Kumano Shigeru,
Ihira Masashi,
Kuromi Mitsuhiro,
Maeda Yasuo,
Matsumoto Eiji,
Nakamura Toshio,
Matsushima Yoshiaki,
Sato Hiroshi,
Matsuda Isao
Publication year - 1990
Publication title -
ecological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.628
H-Index - 68
eISSN - 1440-1703
pISSN - 0912-3814
DOI - 10.1007/bf02347004
Subject(s) - holocene , bay , marine transgression , geology , sedimentary rock , oceanography , diatom , shore , quaternary , paleontology , structural basin
Diatom assemblages of sediments obtained from Kushu Lake and Akkeshi were analyzed in order to clarify the local Holocene sedimentary history. The results revealed the following: 1) Sometime before about 9000 yr B.P., Kushu Lake was originally a freshwater environment. 2) The first marine diatom zone (MD 1 Zone) was deposited on the bottom of the paleo‐Kushu Bay between 8500 and 6000 yr B.P. 3) This site changed to become the bottom of the paleo‐Kushu Lagoon around 6000 yr B.P. owing to the formation of a bay‐mouth bar across the paleo‐Kushu Bay and the first Holocene regression resulted in a freshwater lake at about 4500 yr B.P. 4) At this time, the Akkeshi site changed from a sublittoral shore in a drowned valley to a peat moor. 5) The second Holocene transgression at about 3000 yr B.P. was detected at the Akkeshi site. 6) At Kushu Lake site the occurrence of Mastogloia elliptica between 7000 and 5000 yr B.P. suggested the influx of the Tsushima warm current into the Japan Sea.