15:00 〜 15:15
[MIS28-06] 膠着質底生有孔虫を用いた北西太平洋における白亜紀後期のレアアース泥堆積環境に関する研究
キーワード：膠着質底生有孔虫、遠洋性粘土、レアアース泥、微化石、太平洋、白亜紀
Deep-sea sediments highly enriched in rare-earth elements and yttrium (REY), called REY-rich mud, are widely distributed in the Pacific Ocean [1]. Notably, very high-grade REY-rich mud lies around Minamitorishima Island in the western North Pacific Ocean, and it is expected to be a promising new resource for REY [2]. Some radiolarian fossils in the uppermost part of the chert imply that the REY-rich mud around Minamitorishima Island started to deposit in the Late Cretaceous [3,4].
Pelagic clay including REY-rich mud has deposited very slowly over a long period of time, and thus, are expected to have recorded the history of pelagic environment. However, the water depth greater than the carbonate compensation depth (CCD) and generally low surface productivity hampered preserving calcareous and siliceous fossils, making it difficult to decipher the environmental changes in the pelagic realm.
Here, we focused on a certain type of benthic foraminifers called deep-water agglutinated foraminifers (DWAF). DWAF have agglutinative shells of aluminosilicates that do not dissolve even at depths below the CCD [4] and consist of various species such as those highly dependent on biological production or tolerant of oligotrophic environments [5]. Therefore, it is expected that investigation of DWAF assemblage will provide a new insight into the depositional environments of REY-rich mud. In the presentation, based on the production and species composition of DWAF, we will discuss the environmental conditions during the time of deposition of REY-rich mud around Minamitorishima Island in the Late Cretaceous.
[1] Kato et al. (2011) Nature Geoscience 4, 535-539. [2] Takaya et al. (2018) Scientific Reports 8, 5763. [3] Wightman and Kuhnt (1992) Proc. ODP, Scientific Results 129, 247-264. [4] Nakamura et al. (2016) Geochemical Journal 50, 605-619. [5] Kaminski and Gradstein (2005) Grzybowski Foundation Special Publication 10, 547
Pelagic clay including REY-rich mud has deposited very slowly over a long period of time, and thus, are expected to have recorded the history of pelagic environment. However, the water depth greater than the carbonate compensation depth (CCD) and generally low surface productivity hampered preserving calcareous and siliceous fossils, making it difficult to decipher the environmental changes in the pelagic realm.
Here, we focused on a certain type of benthic foraminifers called deep-water agglutinated foraminifers (DWAF). DWAF have agglutinative shells of aluminosilicates that do not dissolve even at depths below the CCD [4] and consist of various species such as those highly dependent on biological production or tolerant of oligotrophic environments [5]. Therefore, it is expected that investigation of DWAF assemblage will provide a new insight into the depositional environments of REY-rich mud. In the presentation, based on the production and species composition of DWAF, we will discuss the environmental conditions during the time of deposition of REY-rich mud around Minamitorishima Island in the Late Cretaceous.
[1] Kato et al. (2011) Nature Geoscience 4, 535-539. [2] Takaya et al. (2018) Scientific Reports 8, 5763. [3] Wightman and Kuhnt (1992) Proc. ODP, Scientific Results 129, 247-264. [4] Nakamura et al. (2016) Geochemical Journal 50, 605-619. [5] Kaminski and Gradstein (2005) Grzybowski Foundation Special Publication 10, 547