JpGU-AGU Joint Meeting 2017

Presentation information

[EJ] Oral

B (Biogeosciences) » B-PT Paleontology

[B-PT05] [EJ] Decoding the history of Earth: From Hadean to Modern

Wed. May 24, 2017 10:45 AM - 12:15 PM 201B (International Conference Hall 2F)

convener:Tsuyoshi Komiya(Department of Earth Science & Astronomy Graduate School of Arts and Sciences The University of Tokyo), Yasuhiro Kato(Department of Systems Innovation, Graduate School of Engineering, University of Tokyo), Katsuhiko Suzuki(Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology), Chairperson:Tsuyoshi Komiya(Department of Earth Science & Astronomy Graduate School of Arts and Sciences The University of Tokyo)

11:30 AM - 11:45 AM

[BPT05-22] A chemostratigraphic correlation of deep-sea pelagic clays in the North Pacific Ocean: Insights from the ODP Sites 1149 and 1179

*Kazuhide Mimura1, Katsushi Yamamoto1, Kentaro Nakamura1, Kazutaka Yasukawa1,2, Junichiro Ohta3,1, Koichiro Fujinaga2,1, Shiki Machida3,1, Yasuhiro Kato1,2,3 (1.School of Engineering, the University of Tokyo, 2.ORCeNG, Chiba Institute of Technology, 3.JAMSTEC)

Keywords:pelagic clay, chemostratigraphy, REY-rich mud, North Pacific Ocean, ODP Site 1149, ODP Site 1179

Pelagic clay, referred to as red clay, is one of the common types of seafloor sediment, especially in the Pacific Ocean floor [1]. It is known that the pelagic clay deposits at remote areas in the ocean with considerably slow sedimentation rates of only 0.1-0.5 cm/kyr. Recently, this type of sediment is also recognized as a new deep-sea mineral resource. In 2011, Kato et al. [2] reported that some parts of the deep-sea pelagic clay in the Pacific Ocean contain high concentrations of rare-earth elements and yttrium (REY). They defined the pelagic clay containing more than 400 ppm of total REY as “REY-rich mud” and concluded that this sediment could be a prospective resource for the critical elements.
Pelagic clay is, however, not so well studied as other types of sediments, such as carbonate and neritic sediments, probably due to the lack of visible features and little availability of microfossils to determine its depositional age. Therefore, detailed stratigraphy of the pelagic clay layers including REY-rich mud is not well understood, although it deposited throughout the Cenozoic era [3]. To clarify the stratigraphy of the pelagic clay layers including REY-rich mud, analyses of long and fully recovered deep-sea sediment cores are needed. Here we focused on the ODP Sites 1149 and 1179 in the North Pacific Ocean, both of which were recovered continuously from seafloor to basement rock.
In this study, we provide the results of bulk chemical analyses of sediment samples from the ODP cores. By comparing the multi-elemental compositions of these cores and those of GPC3-LL44 [4], we constructed a general chemostratigraphy of pelagic clay layers in the North Pacific Ocean. We also quantified the relative contributions of each geochemical end-member causing the chemostratigraphic variations of the pelagic clay layers. Based on the results, we discuss the deposition processes of pelagic clays including REY-rich mud in the North Pacific Ocean.

[1] Dutkiewicz et al. (2015) Geology 43, 795-798.
[2] Kato et al. (2011) Nature Geoscience 4, 535-539.
[3] Yasukawa et al. (2016) Scientific Reports 6, 29603.
[4] Kyte et al. (1993) Geochemica et Cosmochimica Acta 57, 1719-1740.