日本地球惑星科学連合2015年大会

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セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS32] 地球掘削科学

2015年5月24日(日) 18:15 〜 19:30 コンベンションホール (2F)

コンビーナ:*斎藤 実篤(独立行政法人海洋研究開発機構)、道林 克禎(静岡大学理学研究科地球科学専攻)、廣野 哲朗(大阪大学 大学院 理学研究科 宇宙地球科学専攻)、梅津 慶太(独立行政法人海洋研究開発機構)

18:15 〜 19:30

[MIS32-P02] Last glacial to deglacial biotic changes on the Great Barrier Reef from offshore boreholes

*Marc HUMBLET1Jody M. WEBSTER2Juan carlos BRAGA3Yasufumi IRYU4Don C. POTTS5Yusuke YOKOYAMA6Tezer M. ESAT7Stewart FALLON8William G. THOMPSON9Alexander L. THOMAS10 (1.Dep. of Earth and Planetary Sc., Nagoya Univ.、2.Geocoastal Research Group, Univ. of Sydney、3.Dep. de Estrat. y Paleont., Univ. de Granada、4.Inst. of Geol. and Paleont., Tohoku Univ.、5.Dep. of Ecol. & Evol. Bio., Univ. of California、6.AORI, Univ. of Tokyo、7.ANSTO, Inst. for Env. Res., Australia、8.Res. Sch. of Earth Sc., Austral. Nation. Univ.、9.Lamont-Doherty Earth Observatory, USA、10.School of GeoSciences, Univ. of Edinburgh)

キーワード:IODP Expedition 325, Great Barrier Reef, Coralgal assemblages, Sea level changes, Glacial, Deglacial

IODP Expedition 325 drilled 34 boreholes into submerged reef structures along the shelf edge of the Great Barrier Reef (GBR). The boreholes were drilled between 42 and 167 mbsl at 17 sites along four transects at three geographic locations (Hydrographers Passage, Noggin Pass, and Ribbon Reef). The last glacial to deglacial reef sequence (~8 ka to ~27 ka) varies in thickness from ~5.5 m to ~34 m and consists primarily of coralgal boundstone with various proportions of microbialite. We use a detailed chronostratigraphic scheme based on numerous C14 and U-Th ages to discuss the evolution of the coralgal communities since the last glaciation. Exp. 325 cores show that different phases of sea level change promoted different shallow reef-building coral species at the study sites. The onset of the deglacial (16-19 ka) is characterized by a peak abundance of Seriatopora and Tubipora whereas the following rapid sea level rise (<16 ka) is marked by the dominance of massive Isopora and Acropora with medium- to robust-size branches. The shift in composition of coral communities around 16 ka coincides with the flooding of a pre-LGM MIS2 reef terrace, an event which had a major influence on reef growth and reef composition. We discuss the impact of this event on coralgal communities in the GBR and its significance for Quaternary reef evolution in general.