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

国际海洋发现计划（IODP）371（塔斯曼前沿俯冲开始和古近纪气候，7月27日至9月26日。2017年）钻探了六个新地点，共回收了2506米的白垩纪至更新世沉积物和火山岩。Exp的记录。371与Cadart钻孔中陆上回收的沉积物相结合，Cadart钻孔包括1999年在布赖尔（新喀里多尼亚中部）附近钻探的约1900 m的上白垩纪-上始新世沉积物。Exp的主要目的。371号正在通过地震反射体分析确定该地区广泛的始新世中期会聚变形、逆断层和隆升的年代。这一事件，解释为汤加Kermadec俯冲开始的前兆，也可能与全球始新世气候周转从变暖趋势达到峰值与早始新世气候最佳（EECO），随后一般中晚始新世冷却。太平洋板块向西俯冲到大洋地壳之下，而不是只发生在美洲科迪勒拉大陆地壳之下，可能导致pCO 2的显著下降，从而导致全球变冷。371和Cadart钻孔的沉积物，2）使用该框架来确定西南太平洋地区的构造演化，如岩性变化所反映的（例如粘土含量的变化，火山物质，以及沉积高能结构如滑塌的存在/不存在）。371将用于评估全球气候变化期间陆地上化学风化的强度。硅酸盐矿物的化学风化，随后是海洋碳酸盐的沉积，是缓冲大气pCO 2的唯一长期机制，这反过来又调节了全球平均温度。来自站点U1511（塔斯曼深海平原）的初步数据显示，在始新世早期（即EECO期间）沉积赤铁矿（源自澳大利亚大陆）相对富集，随后在随后的始新世中晚期有所减少。根据Dallanave等人[2010，Geochem.地球物理学家。地球系统11（7）]，碎屑赤铁矿的变化有效地跟踪沉积物源区的化学风化速率。本项目的目标3）是详细监测始新世以来塔斯曼深海平原沉积物中赤铁矿含量的变化，评估澳大利亚大陆化学风化的强度。本项目所获得的综合数据集将描绘一幅置于共同时间框架内的完整的构造和气候演化图，这为阐明大规模构造与全球气候之间的联系提供了可能性。

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.