5:15 PM - 7:15 PM
[SCG55-P11] Carbonate Dissolution Variations Over the Past 500,000 Years on the Southwestern Slope of Tamu Massif, Shatsky Rise
Keywords:Shatsky Rise, Carbonate Compensation Depth, Carbon cycle, Glacial interglacial cycle
The carbon cycle is closely related to past climate changes. During the Quaternary period (2.58 million years ago to the present), glacial-interglacial cycles were accompanied by fluctuations in global mean temperature and atmospheric CO2 concentrations[1]. The difference in atmospheric CO2 concentrations between the glacial and interglacial periods reached 90 p.p.m.v., but its mechanism has long been debated as the "glacial carbon reservoir problem" [2]. The deep ocean is the largest carbon reservoir (38000 GtC) in the Earth's surface system, and it is one of the potential reservoirs of the massive carbon during the glacial periods. From this perspective, many studies have investigated bulk carbonate, foraminifera, and calcareous nannofossil dissolutions in the deep-sea sediments during the last 500 kyrs to 1 myrs [3-7]. However, previous research on the Pacific Ocean mainly focused on the equatorial area.
Here, this study aims to reconstruct the variations in carbonate compensation depth (CCD) over the last 500 kyrs, by using the four piston cores (KH-24-1 PC01-PC04) collected from the southwestern slope of Tamu Massif, Shatsky Rise. These core samples were collected from depths across the carbonate compensation depth (CCD) in the present day. The major lithology in PC01 is nannofossil ooze, whereas PC03 and PC04 are mainly composed of pelagic clay. Alternating layers of nannofossil ooze and pelagic clay were observed in PC02. This study correlated the four cores using paleomagnetic intensity, L*a*b* color values, and XRF core scanning results. The dating results suggest that carbonate was well-preserved during glacial periods, whereas dissolved more extensively during interglacial periods. Furthermore, we confirmed that CCD in the study area was relatively stable, but carbonate critical depth (CCrD; the depth with 10% of bulk carbonate content) showed a variation of approximately 900 m. The carbonate dissolution could be related to the changes in bioproductivity and deep ocean circulations.
[1]Petit et al. (1999) Nature, 399(6735), 429-436. [2] Okazaki(2015) Geochemistry, 49(3), 131-152. [3] Wu and Berger, (1991) Marine Geology, 96(3-4), 193-209. [4] Kimoto et al., (2003) Marine Micropaleontology, 47(3-4), 227-251. [5] Zhang et al., (2007) Marine Micropaleontology, 64(3-4), 121-140. [6] Farrell and Prell, (1989) Paleoceanography, 4(4), 447-466. [7] Murray et al., (2000) Paleoceanography, 15(6), 570-592.
Here, this study aims to reconstruct the variations in carbonate compensation depth (CCD) over the last 500 kyrs, by using the four piston cores (KH-24-1 PC01-PC04) collected from the southwestern slope of Tamu Massif, Shatsky Rise. These core samples were collected from depths across the carbonate compensation depth (CCD) in the present day. The major lithology in PC01 is nannofossil ooze, whereas PC03 and PC04 are mainly composed of pelagic clay. Alternating layers of nannofossil ooze and pelagic clay were observed in PC02. This study correlated the four cores using paleomagnetic intensity, L*a*b* color values, and XRF core scanning results. The dating results suggest that carbonate was well-preserved during glacial periods, whereas dissolved more extensively during interglacial periods. Furthermore, we confirmed that CCD in the study area was relatively stable, but carbonate critical depth (CCrD; the depth with 10% of bulk carbonate content) showed a variation of approximately 900 m. The carbonate dissolution could be related to the changes in bioproductivity and deep ocean circulations.
[1]Petit et al. (1999) Nature, 399(6735), 429-436. [2] Okazaki(2015) Geochemistry, 49(3), 131-152. [3] Wu and Berger, (1991) Marine Geology, 96(3-4), 193-209. [4] Kimoto et al., (2003) Marine Micropaleontology, 47(3-4), 227-251. [5] Zhang et al., (2007) Marine Micropaleontology, 64(3-4), 121-140. [6] Farrell and Prell, (1989) Paleoceanography, 4(4), 447-466. [7] Murray et al., (2000) Paleoceanography, 15(6), 570-592.