Late Miocene-mid-Pliocene tectonically induced formation of the semi-closed Japan Sea, inferred from seawater Nd isotopes

Yukiko Kozaka, Keiji Horikawa, Yoshihiro Asahara, Hiroshi Amakawa, Yusuke Okazaki

研究成果: ジャーナルへの寄稿記事

2 引用 (Scopus)

抄録

The Japan Sea in the western North Pacific was connected to the deep Pacific via deep seaways before it became a semi-closed marginal sea. However, the timing of the semi-closure and its cause(s) remain debatable. To further constrain the timing, for the first time we analyzed Nd isotopic compositions of fossil fish teeth and fish debris deposited in the Japan Sea (Integrated Ocean Drilling Program [IODP] Site U1425, ~2000 m water depth) over the past 10 m.y. Neodymium isotope values (-4.5 to -3.2 εNd) in the Japan Sea prior to 4.5 Ma illustrate that the deep Japan Sea was composed of an admixture of less-radiogenic Lower Circumpolar Deep Water (avg. -4.3 εNd) and more-radiogenic North Pacific Deep Water (avg. -2.2 εNd), potentially with inflow from the Okhotsk Sea. At 4.5 Ma, εNd values fell to -5.5 εNd within a span of 140 k.y., suggesting that the deep-water communication between the Japan Sea and the North Pacific rapidly declined. We argue that active mountain building in the northern Japan arc, initiated by accelerated Pacific plate motion from the late Miocene to mid-Pliocene, caused the shallowing/narrowing of the Japan Sea- Pacific seaways and rapidly made the Japan Sea semi-closed at 4.5 Ma. As a result, the Japan Sea circulation patterns were realigned; a cyclonic circulation was developed and drew less-radiogenic Amur River-influenced Okhotsk Sea water into the Japan Sea.

元の言語英語
ページ(範囲)903-906
ページ数4
ジャーナルGeology
46
発行部数10
DOI
出版物ステータス出版済み - 10 1 2018

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Pliocene
Miocene
isotope
seawater
deep water
neodymium isotope
marginal sea
sea
plate motion
Pacific plate
fish
Ocean Drilling Program
tooth
deep sea
water depth
inflow
isotopic composition
communication
fossil
mountain

All Science Journal Classification (ASJC) codes

  • Geology

これを引用

Late Miocene-mid-Pliocene tectonically induced formation of the semi-closed Japan Sea, inferred from seawater Nd isotopes. / Kozaka, Yukiko; Horikawa, Keiji; Asahara, Yoshihiro; Amakawa, Hiroshi; Okazaki, Yusuke.

:: Geology, 巻 46, 番号 10, 01.10.2018, p. 903-906.

研究成果: ジャーナルへの寄稿記事

Kozaka, Yukiko ; Horikawa, Keiji ; Asahara, Yoshihiro ; Amakawa, Hiroshi ; Okazaki, Yusuke. / Late Miocene-mid-Pliocene tectonically induced formation of the semi-closed Japan Sea, inferred from seawater Nd isotopes. :: Geology. 2018 ; 巻 46, 番号 10. pp. 903-906.
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abstract = "The Japan Sea in the western North Pacific was connected to the deep Pacific via deep seaways before it became a semi-closed marginal sea. However, the timing of the semi-closure and its cause(s) remain debatable. To further constrain the timing, for the first time we analyzed Nd isotopic compositions of fossil fish teeth and fish debris deposited in the Japan Sea (Integrated Ocean Drilling Program [IODP] Site U1425, ~2000 m water depth) over the past 10 m.y. Neodymium isotope values (-4.5 to -3.2 εNd) in the Japan Sea prior to 4.5 Ma illustrate that the deep Japan Sea was composed of an admixture of less-radiogenic Lower Circumpolar Deep Water (avg. -4.3 εNd) and more-radiogenic North Pacific Deep Water (avg. -2.2 εNd), potentially with inflow from the Okhotsk Sea. At 4.5 Ma, εNd values fell to -5.5 εNd within a span of 140 k.y., suggesting that the deep-water communication between the Japan Sea and the North Pacific rapidly declined. We argue that active mountain building in the northern Japan arc, initiated by accelerated Pacific plate motion from the late Miocene to mid-Pliocene, caused the shallowing/narrowing of the Japan Sea- Pacific seaways and rapidly made the Japan Sea semi-closed at 4.5 Ma. As a result, the Japan Sea circulation patterns were realigned; a cyclonic circulation was developed and drew less-radiogenic Amur River-influenced Okhotsk Sea water into the Japan Sea.",
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