Exploring the coupling between plate tectonic and climate evolution: Eocene–Oligocene chronology of the southwest Pacific

探索板块构造与气候演化之间的耦合：西南太平洋始新世渐新世年代学

• 批准号: 408178503
• 负责人: Dr. Edoardo Dallanave, Ph.D.
• 金额: --
• 依托单位: Fachgebiet Marine Geophysik
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/408178503?language=en
• 关键词: Exploring; coupling; between; plate; tectonic

International Ocean Discovery Program (IODP) Exp. 371 (Tasman Frontier Subduction Initiation and Paleogene Climate, 27th July to 26th Sept. 2017) drilled six new sites recovering a total of 2506 m of Cretaceous to Pleistocene sediments and volcanic rocks. The record of Exp. 371 is integrated with the sediments recovered onshore in the Cadart borehole, which consists of ~1900 m of Upper Cretaceous–upper Eocene sediments drilled in 1999 near Bourail (central New Caledonia). The main objective of Exp. 371 is dating the widespread middle Eocene convergent deformation, reverse faulting, and uplift recorded in the area by analyses of seismic reflectors. This event, interpreted as the precursor of the Tonga-Kermadec subduction initiation, may also coincide with the global Eocene climate turnover from the warming trend peaking with the early Eocene climate optimum (EECO) to the ensuing general middle–late Eocene cooling. Pacific Plate westward-dominated subduction beneath oceanic crust, instead of subduction only occurring beneath the continental crust of the American cordillera, might have caused a significant drop in pCO2 and thus global cooling.The first objectives of this project are 1) the construction of a magnetic-polarity-based chronological framework of the sediments recovered during IODP Exp. 371 and sediments of the Cadart borehole, 2) use this framework to date the tectonic evolution of the Southwest Pacific area as reflected by the lithological variations (e.g. variations in clay content, volcanic material, and presence/absence of sedimentary high-energy structures like slumps).Data from Exp. 371 will be used to evaluate the intensity of chemical weathering on land during times of global climate variations. Chemical weathering of silicate minerals, followed by deposition of marine carbonate, is the only long-term mechanism buffering the atmospheric pCO2, which in turn modulates the average global temperatures. Preliminary data from Site U1511 (Tasman abyssal plain) shows a relative enrichment in sedimentary hematite (originated from the Australian continent) during the early Eocene (i.e. during the EECO), followed by a decrease over the ensuing middle–late Eocene. Following the idea proposed by Dallanave et al. [2010, Geochem. Geophys. Geosyst. 11(7)], variations of detrital hematite trace efficiently the rates of chemical weathering at the sediment source area. Objective 3) of this proposal is monitoring in detail the hematite content variations of the sediments deposited on the Tasman abyssal plain over the Eocene, evaluating the intensity of chemical weathering on the Australian continent.The integrated dataset obtained in this project will depict a complete tectonic and climate evolution picture placed in a common time frame, giving the possibility to shed light on the connection between large-scale tectonics and global climate.

国际海洋发现计划（IODP） Exp. 371 （Tasman Frontier俯冲起始和古近系气候，2017年7月27日至9月26日）钻探了6个新地点，共回收了2506米的白垩纪至更新世沉积物和火山岩。Exp. 371的记录与Cadart钻孔在陆上回收的沉积物相结合，该钻孔包括1999年在Bourail（新喀里多尼亚中部）附近钻探的约1900 m的上白垩统-上始新统沉积物。Exp. 371的主要目的是通过分析地震反射体来确定该地区广泛的中始新世会聚变形、逆断层和隆起的年代。这一事件被解释为汤加-克马德克俯冲起始的前兆，也可能与全球始新世气候从早期始新世气候最佳（EECO）的变暖趋势达到峰值到随后的始新世中后期普遍降温的转变相吻合。太平洋板块向西主导的大洋地壳下的俯冲，而不是只发生在美洲科迪勒拉大陆地壳下的俯冲，可能会导致二氧化碳分压的显著下降，从而导致全球变冷。该项目的首要目标是：1)为IODP Exp. 371期间回收的沉积物和Cadart钻孔的沉积物建立一个基于磁极性的年代学框架；2)利用这个框架来确定西南太平洋地区的构造演化，这是由岩性变化（例如粘土含量、火山物质的变化以及沉积高能结构（如滑坡）的存在/缺失）所反映的。Exp. 371的数据将用于评估全球气候变化时期陆地化学风化的强度。硅酸盐矿物的化学风化作用，随后是海洋碳酸盐的沉积，是缓冲大气二氧化碳分压的唯一长期机制，二氧化碳分压反过来调节全球平均温度。U1511遗址（Tasman深海平原）的初步资料显示，在始新世早期（即EECO时期），沉积赤铁矿（源自澳大利亚大陆）相对富集，随后在始新世中晚期减少。根据Dallanave et al. [2010, Geochem.]地球物理学。地球系统，11(7)]，碎屑赤铁矿的变化有效地反映了沉积物源区的化学风化速率。目的3)详细监测塔斯曼深海平原始新世沉积的赤铁矿含量变化，评价澳大利亚大陆化学风化强度。本项目获得的综合数据集将描绘一个在共同时间框架内的完整的构造和气候演化图景，为揭示大尺度构造与全球气候之间的联系提供了可能。