15:30 〜 15:48
[BPT01-07] Long term size changes of the Middle Miocene planktonic foraminifera in the western equatorial Pacific
キーワード：体サイズ、浮遊性有孔虫、リリパット効果、コープの法則、中期中新世
Planktonic foraminifera is an oceanic free-floating single celled protozoa. In the modern ocean, it is classified into approximately 50 species. The oldest planktonic foraminiferal fossil records are appeared from the Jurassic. Carbonate shells of planktonic foraminifera are well preserved into marine sediments especially from ocean drilled cores. The successive and rich appearance of the fossils provide good paleoenvironmental proxies with high special-temporal resolution by chemical and morphological analyses.
In this study, we focused “size” of planktonic foraminiferal shell to consider evolution models about size such as “Lilliput Effect” and “Giantism”. These models have a potential to make clear what the relationship between organism response and environmental fluctuation. The size analysis of planktonic foraminifera has a significant potential for investigation of “Lilliput Effect” and “Giantism” because a size analysis to investigate these evolution models require a lot of individuals of single taxon. Another reason should be pointed out that planktonic foraminifera shows accretion growth by adding a new chamber on its penultimate chamber, therefore the size of planktonic foraminifera well reflects the ontogenic pattern.
Our study is composed of two parts as described bellow:
1. This study aims to reconstruct the temporal size change of Paragloborotalia siakensis (LeRoy) during Middle Miocene in the western equatorial Pacific. The core samples we used in this study were drilled at ODP Site 807. The successive sediments well preserved foraminiferal shells, and recorded the transition from the relatively warm face (MMCO: Mid-Miocene Climatic Optimum) to the colder mode Mi-3 with the expansion of the Eastern Antarctica Ice Sheet.
2. In order to consider the model about “Dwarfing” and “Giantism” of P. siakensis in equatorial Pacific, we compared the size change at ODP Site 807 with those of IODP Sites U1337 and U1338 drilled at the eastern equatorial Pacific.
In this study, we focused “size” of planktonic foraminiferal shell to consider evolution models about size such as “Lilliput Effect” and “Giantism”. These models have a potential to make clear what the relationship between organism response and environmental fluctuation. The size analysis of planktonic foraminifera has a significant potential for investigation of “Lilliput Effect” and “Giantism” because a size analysis to investigate these evolution models require a lot of individuals of single taxon. Another reason should be pointed out that planktonic foraminifera shows accretion growth by adding a new chamber on its penultimate chamber, therefore the size of planktonic foraminifera well reflects the ontogenic pattern.
Our study is composed of two parts as described bellow:
1. This study aims to reconstruct the temporal size change of Paragloborotalia siakensis (LeRoy) during Middle Miocene in the western equatorial Pacific. The core samples we used in this study were drilled at ODP Site 807. The successive sediments well preserved foraminiferal shells, and recorded the transition from the relatively warm face (MMCO: Mid-Miocene Climatic Optimum) to the colder mode Mi-3 with the expansion of the Eastern Antarctica Ice Sheet.
2. In order to consider the model about “Dwarfing” and “Giantism” of P. siakensis in equatorial Pacific, we compared the size change at ODP Site 807 with those of IODP Sites U1337 and U1338 drilled at the eastern equatorial Pacific.