Japan Geoscience Union Meeting 2014

Presentation information

Oral

Symbol B (Biogeosciences) » B-PT Paleontology

[B-PT25_2PM1] Biotic history and its relation to the Earth history

Fri. May 2, 2014 2:15 PM - 4:00 PM 416 (4F)

Convener:*Isao Motoyama(Department of Earth and Environmental Sciences, Yamagata University), Takao Ubukata(Institute of Geosciences, Faculty of Science, Shizuoka University), Chair:Takao Ubukata(Institute of Geosciences, Faculty of Science, Shizuoka University), Isao Motoyama(Department of Earth and Environmental Sciences, Yamagata University)

2:45 PM - 3:00 PM

[BPT25-03] Neodymium isotopic signature for deep/intermediate water formation in the late Cretaceous northwestern Pacific

*Kazuyoshi MORIYA1, Mathieu MOIROUD2, Emmanuelle PUCEAT2, Yannick DONNADIEU3, Germain BAYON4, Jean-francois DECONINCK2, Maud BOYET5 (1.Dep. Earth Sci., Kanazawa Univ., 2.UMR CNRS Lab. Biogeosciences, Univ. Bourgogne, 3.UMR CEA/CNRS Lab. Sci. Climat Environ., CE Saclay, 4.IFREMER,Unite Recherche Geosciences Marines, 5.UMR CNRS Labo. Magmas Volcans, Univ. Blaise Pascal)

Keywords:Cretaceous, Ocean circulation, Neodymium isotopes, North Pacific, Deep water, Intermediate Water

The Cretaceous is known to be one of the archetypal greenhouse periods, and intensively studied for evaluating the climate sensitively in the high pCO2 region. The meridional sea surface temperature distribution, secular changes in sea surface and deep water temperatures have also been discussed globally. In addition to the thermal structure, analyses of ocean circulations on the basis of neodymium isotope signatures become more popular especially in the Atlantic Ocean. On the other hand, the ocean circulation in the Pacific Ocean is still uncertain, because of fundamental lack of deep sea sediments in the Pacific. In this study, instead of deep sea sediments, fore arc basin sediments have been utilized for discussing the ocean circulation in the late Cretaceous (late Turonian through early Campanian) northwestern Pacific.Neodymium isotopic signatures in fish remains obtained from clayey sediments in the Yezo Group show highly radiogenic values of −1 to −2 ε-unit. These values are significantly higher than those in the Atlantic and the equatorial Pacific. This result indicates the presence of highly radiogenic intermediate/deep water formation in the northwestern Pacific, because it is expected that the radiogenic neodymium has been delivered from volcanic arcs in the northwestern Pacific. This results is also supported by climate models showing the potential deep water formation in the late Cretaceous northwestern Pacific.