17:15 〜 18:45
[BPT02-P11] A simple analysis to reconstruct the basic information of foraminifera and ice-rafted debris using image analysis.
キーワード：IODP、EXP395、ice-rafted debris、Planktonic foraminifera
The planktonic foraminifera Neogloborotalia pachyderma (Ehrenberg), a dominant species in high latitude regions, is well studied as the paleo proxy. Also, the genetic knowledge is well accumulated. Previous studies indicated the synchronous size change of N. pachyderma between the North Atlantic and Pacific from the middle Pleistocene to the Present. This unique size distribution is a clue to understanding the evolution of the planktonic foraminifera and the relationship between body size and the environment.
The ice-rafted debris (IRD) is an established proxy to reconstruct the ice-sheet history and is found from the sediment particle over 63 µm sieve. The mesh size is common with the process for foraminiferal analysis. Therefore, we aimed to develop a simple method to reconstruct the abundance of planktonic foraminifera and IRD which are powerful proxies to understand the paleoclimate in the high latitude region. The reason why we tried to make it simple is that we are assuming this method will be conducted as routine in the early part of the process with a low cost.
We used the sediment core samples drilled by the International Ocean Discovery Program Expedition 395C Site U1562 Hole A at the North Atlantic. Expeditions 395C (5th June–6th August 2021) and 395 (12th June–12th August 2023) are designed (1) to test contrasting hypotheses for the formation of VSRs, (2) to understand temporal changes in ocean circulation and explore connections with plume activity, and (3) to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and varying sediment thickness and crustal architecture. We succeeded in obtaining the entire sediment package from three drifts (Eric, Björn, and Gardar).
Site U1562 is located in the east of Björn drift and has a relatively stable sedimentation rate. Samples were freeze-dried, washed on the sieve with an open diameter of 63 µm, separated, and analyzed. The images of all particles scattered on the tray are obtained by the digital microscope automatically. By image analysis, we succeed in measuring the count (abundance), maximum diameter, area, perimeter, circularity, and color.
The temporal size record of planktonic foraminifera from the Pleistocene to the Present showed a harmonic trend with previous studies in the North Atlantic, and the trend of giantism reflected the improvement of the trophic condition.
The ice-rafted debris (IRD) is an established proxy to reconstruct the ice-sheet history and is found from the sediment particle over 63 µm sieve. The mesh size is common with the process for foraminiferal analysis. Therefore, we aimed to develop a simple method to reconstruct the abundance of planktonic foraminifera and IRD which are powerful proxies to understand the paleoclimate in the high latitude region. The reason why we tried to make it simple is that we are assuming this method will be conducted as routine in the early part of the process with a low cost.
We used the sediment core samples drilled by the International Ocean Discovery Program Expedition 395C Site U1562 Hole A at the North Atlantic. Expeditions 395C (5th June–6th August 2021) and 395 (12th June–12th August 2023) are designed (1) to test contrasting hypotheses for the formation of VSRs, (2) to understand temporal changes in ocean circulation and explore connections with plume activity, and (3) to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and varying sediment thickness and crustal architecture. We succeeded in obtaining the entire sediment package from three drifts (Eric, Björn, and Gardar).
Site U1562 is located in the east of Björn drift and has a relatively stable sedimentation rate. Samples were freeze-dried, washed on the sieve with an open diameter of 63 µm, separated, and analyzed. The images of all particles scattered on the tray are obtained by the digital microscope automatically. By image analysis, we succeed in measuring the count (abundance), maximum diameter, area, perimeter, circularity, and color.
The temporal size record of planktonic foraminifera from the Pleistocene to the Present showed a harmonic trend with previous studies in the North Atlantic, and the trend of giantism reflected the improvement of the trophic condition.