Japan Geoscience Union Meeting 2023

Presentation information

[E] Online Poster

B (Biogeosciences ) » B-PT Paleontology

[B-PT03] Biomineralization and Geochemistry of Proxies

Thu. May 25, 2023 1:45 PM - 3:15 PM Online Poster Zoom Room (11) (Online Poster)

convener:Takashi Toyofuku(Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Hiroshi Kitazato(Tokyo University of Marine Science and Technology (TUMSAT)), Jelle Bijma(Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung), Kotaro Hirose(Institute of Natural and Environmental Sciences, University of Hyogo)


On-site poster schedule(2023/5/26 17:15-18:45)

1:45 PM - 3:15 PM

[BPT03-P04] Three-dimensional parameters (volume and density) of planktonic foraminiferal fossils in the core as potential paleoenvironmental proxies

*Shunichi Kinoshita1, Quan Wang2, Azumi Kuroyanagi3, Masafumi MURAYAMA4, Yurika Ujiie5, Hodaka Kawahata6 (1.Department of Geology and Paleontology, National Museum of Nature and Science, 2.Atmosphere Ocean Research Institute, the University of Tokyo, 3.Tohoku University Museum, The Center for Academic Resources and Archives, Tohoku University, 4.Faculty of Agriculture and Marine Science, Kochi University, 5.Center for Advanced Marine Core Research, Kochi University, 6.School of Creative Science and Engineering, the Faculty of Science and Engineering, Waseda University)

Keywords:planktic foraminifers, paleoenvironmental proxy, micro X-ray computed tomography

Various marine organisms, such as corals, coccoliths, and foraminifers, use carbonate ions in the surrounding seawater for their skeleton and shell production. There is some evidence that carbonate saturation affects foraminiferal shells, and foraminiferal shell production is known to be sensitive to increases in pCO2. Size-normalized weights of foraminiferal shells have been used to estimate surface carbonate systems. However, it is unclear which parameters of foraminiferal shells are reflected in the size-normalized weights. Whether it is due to shell thickness, shell density, or both is considered obscure. Therefore, the relationship between foraminiferal shell parameters and environmental parameters, especially with three-dimensional parameters such as shell volume (which may reflect mean shell thickness) and density, is still unclear.
In this study, we measured the shell size-normalized weight, shell volume, and shell density of the planktic foraminifera Globigerinoides ruber (white) in core MD98-2196 and discussed the relationship between these shell parameters and environmental parameters (pCO2 and SST). Furthermore, it was also aimed to explore the possibility that each shell parameter could be a proxy for estimating paleoenvironmental conditions. By using high-resolution micro X-ray computed tomography, it was possible to precisely and quantitatively measuring the three-dimensional parameters. The results suggest that shell size-normalized weight and shell volume may be negatively correlated with marine environmental parameters (pCO2and SST). It was also found that these two parameters might be more influenced by pCO2 than by SST. On the other hand, shell density did not show any change from 3-100 ka, thus it is expected to maintain a constant value. Therefore, the variation in size-normalized weight likely reflects the mass of the shell, and no effect of quality (i.e., density) was observed. Furthermore, the results suggest that shell volume could be used as an environmental proxy in addition to the conventionally used size-normalized weight. On the other hand, shell density was controlled nearly constant, so future work is required to determine what environmental parameters are contributing to the response of foraminifers to changes in shell density during foraminiferal shell building.