Reconstruction of Quaternary paleoenvironment in the Indian and Western Pacific Oceans based upon floral analysis of calcareous nannofossils.

基于钙质超微化石的植物分析重建印度洋和西太平洋第四纪古环境。

• 批准号: 05454001
• 负责人: OKADA Hisatake
• 金额: $ 4.74万
• 依托单位: HOKKAIDO UNIVERSITY (1995)Yamagata University (1993-1994)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05454001/
• 关键词: Calcareous nannofossils; Paleoenvironment; Quaternary; Indian Ocean; Monsoon; オーストラリア西岸域; ルーウエン海流

Calcareous nannoflora in four cores, three from the tropical to temperate regions of the eastern Indian Ocean and one from off-coast of SE Australia, were analyzed to reconstruct Quaternary paleoceanographic history of the Indian and Western Pacific Oceans. Followings are the major results of this investigation.1) Relative abundances of three lower-photic taxa fluctuated synchronously, thus the stratigraphic change in Florisphaera profunda, which is generally the only species preserved in deep sea sediment, was proven to be an accurate indicator of the strata stability in euphotic water.2) The percentage abundance of F.profunda indicates a ca. 100 kyr cyclicity of the monsoonal strength corresponding to the orbital eccentricity, and the significant reduction in F.profunda abundance indicates significant weakening of the monsoon during the interglacial periods.3) Influence of the Leeuwin Current lessened greatly during the glacial periods, and the reduction in F.profunda abundance in two mid-latitude cores taken from off-coast of the western Australia indicates a lower lower-photic temperature which was resulted by an increased influence of the Western Australian Current.4) The Leeuwin Current flows continuously at the northern margin of the Southern Ocean for the last 14 kyr, and the complete disappearance of tropical taxa confirmed the disappearance of the current during the past glacial periods.

对4个岩心的钙质纳米植物区系进行了分析，其中3个岩心位于东印度洋热带至温带地区，1个岩心位于澳大利亚东南部近海，目的是重建印度洋和西太平洋第四纪古海洋学历史。以下是本次调查的主要结果。(1) 3个低光分类群的相对丰度同步波动，证明了深Florisphaera profunda的地层变化是深光水体中地层稳定性的准确指标，而深Florisphaera profunda通常是深海沉积物中唯一保存的物种。(2)深草丰度百分比反映了与轨道偏心率相对应的季风强度周期约为100 kyr，深草丰度的显著减少表明间冰期季风明显减弱。(3) Leeuwin洋流的影响在冰期显著减弱，在西澳大利亚近海的两个中纬度岩心中f.l profunda丰度的减少表明，由于西澳大利亚洋流的影响增强，南大洋北缘Leeuwin洋流在过去14 kyr中持续流动。热带分类群的完全消失证实了过去冰期洋流的消失。

项目成果

Okada,H. and Matsuoka,M.: "Lower-photic nannoflora as an indicator of the late Quatermary monsooual paleo-reccord in the tropical Indian Oceam." Proceedings of ODP and Marine Biosphere International Conference, Aberystwyth. (in press). (1996)

冈田，H.

Okada, H.and Matsuoka, M.: "Lower-photic nannoflora as an indicator of the late Quaternary monsoonal palaeo-record in the tropical Indian Ocean." Proceedings of the ODP and Marine Biosphaere International Conference. Aberystwyth. (in press). (1996)

Okada, H. 和 Matsuoka, M.：“低光纳米植物群作为热带印度洋第四纪晚期季风古记录的指标。”

Okada, H.and Wells, P.: "Late Quaternary nannofossil indicators of climate change in two deep-sea cores associated with the Leeuwin Current off Western Australia." Paleoceanogr. Paleoclimatol. Paleoecol.(in press). (1996)

Okada, H. 和 Wells, P.：“与西澳大利亚附近露文洋流相关的两个深海核心的气候变化的晚第四纪超微化石指标。”

Wells, P.and Okada, H.: "Holocene and Pleistocene glacial paleoceanography off southeastern Australia, based on foraminifera and nannofossils in Vema cored hole V18-222." Austral. Jour. Earth Sciences. Vol. 43/5 (in press). (1996)

Wells, P. 和 Okada, H.：“澳大利亚东南部的全新世和更新世冰川古海洋学，基于 Vema 取芯孔 V18-222 中的有孔虫和超微化石。”

Wells,P. and Okada,H: "Holocene and Pleistocene glacial Palerceanography off Southeastern Australia, based on foraminife ra and nannofossils in vema hole V18-222" Austral.Jour.Earth Science. (in press). (1996)

威尔斯，P.