17:15 〜 18:45
[MIS12-P31] Secular changes in intermediate water flow at Campbell Plateau, south of New Zealand during the Eocene and early Oligocene
The changes in ocean circulations during the Eocene and early Oligocene were controlled by large-scale tectonic events, such as the openings of the Drake Passage between the Pacific and Atlantic, and the Tasman Gateway between the Indian and Pacific [1,2]. These two events resulted in the formation of eastward water circulations called “Antarctic Circumpolar Current” (ACC) and global scale cooling. Bijl et al. (2013) revealed the onset of shallow seawater exchange, flowing from the Pacific to Indian Ocean, around the Tasman Gateway at 49 Ma [3]. Moreover, Scher et al. (2015) reported that deep water flow from the Indian to Pacific Ocean related to the ACC, started at approximately 30 Ma [2]. However, a long-term Paleogene record of intermediate water flow in the high-latitude Pacific is limited and sparse (i.e., Huck et al., 2017 [4]).
To discuss past oceanic circulations, previous research reconstructed seawater Nd isotopic ratios, archived in foraminifers, fish teeth, and carbonate fractions [5]. Seawater Nd isotopic ratios vary in each oceanic basin, because neodymium has a shorter residence time (~500 years) than oceanic circulations (~2000 years), and different regional values reflecting local Nd source materials [6]. Therefore, seawater Nd isotopic ratios in the archive materials contain information on the source of water mass at the timing of their depositions. In addition, rare earth element concentrations of deep-sea sediments are generally controlled by source material changes, which could record depositional environments [7].
Here, we show Nd isotopic ratios and rare earth element compositions of carbonate fractions and bulk sediments at International Ocean Discovery Program (IODP) Site U1553. These geochemical features constrain source materials and intermediate water flow paths in the high-latitude Pacific Ocean during the Eocene and early Oligocene.
[1] Scher and Martin (2004) Earth and Planetary Science Letters 228 (2004) 391–405. [2] Scher et al. (2015) Nature, 523, 580–583. [3] Bijl et al. (2013) Proc. Natl. Acad. Sci. U.S.A. 110, 9645–9650. [4] Huck et al. (2017) Paleoceanography 32, 674–691. [5] Tachikawa et al. (2017) Chem. Geol. 457, 131–148. [6] Tachikawa et al. (2003). J. Geophys. Res. 108, 3254. [7] Tanaka et al. (2022) Geochemistry, Geophys. Geosystems 23, e2021GC009729.
To discuss past oceanic circulations, previous research reconstructed seawater Nd isotopic ratios, archived in foraminifers, fish teeth, and carbonate fractions [5]. Seawater Nd isotopic ratios vary in each oceanic basin, because neodymium has a shorter residence time (~500 years) than oceanic circulations (~2000 years), and different regional values reflecting local Nd source materials [6]. Therefore, seawater Nd isotopic ratios in the archive materials contain information on the source of water mass at the timing of their depositions. In addition, rare earth element concentrations of deep-sea sediments are generally controlled by source material changes, which could record depositional environments [7].
Here, we show Nd isotopic ratios and rare earth element compositions of carbonate fractions and bulk sediments at International Ocean Discovery Program (IODP) Site U1553. These geochemical features constrain source materials and intermediate water flow paths in the high-latitude Pacific Ocean during the Eocene and early Oligocene.
[1] Scher and Martin (2004) Earth and Planetary Science Letters 228 (2004) 391–405. [2] Scher et al. (2015) Nature, 523, 580–583. [3] Bijl et al. (2013) Proc. Natl. Acad. Sci. U.S.A. 110, 9645–9650. [4] Huck et al. (2017) Paleoceanography 32, 674–691. [5] Tachikawa et al. (2017) Chem. Geol. 457, 131–148. [6] Tachikawa et al. (2003). J. Geophys. Res. 108, 3254. [7] Tanaka et al. (2022) Geochemistry, Geophys. Geosystems 23, e2021GC009729.