Early Cenozoic climate and tectonic evolution of the southwest Pacific Ocean

古新世-始新世世界被温暖的条件和没有永久的极地冰所支配。古新世晚期-始新世早期气候变暖急剧下降，达到早始新世气候最佳时期(EECO；~52-50 Ma)，随后在始新世中晚期出现降温趋势，最终将地球推向今天的极地冰川状态。早古近纪的长期气候历史也被几次短暂(约10^3-10^5年)的高温事件所打断。虽然北半球有许多露头和深海磁极性刻度记录，但南半球仍然缺乏足够数量的连续和刻度良好的地层记录，特别是在新生代早期热输运中发挥重要作用的南太平洋。鉴于新西兰南岛出露的晚古新世-中始新世海洋记录最近获得了高质量的古地磁结果，这里我们提议对出露在Tora(新西兰北岛东南部Wairarapa)的Pukemuri和Awhaiti溪段以及Koumac-Gomen地区(新喀里多尼亚Grande-Terre岛)出露的Pain de Sucre、Sommet Khian和Thonon剖面进行古地磁和岩石磁学研究。这些记录将通过对DSDP站点206-210(21段，西南太平洋)的磁性地层学分析加以整合。目标区段的磁极反转序列将用于与国际地磁极时间尺度的对比，从而确定一个可靠的沉积年龄模型。Koumac-Gomen剖面的成熟年代学将限制沉积杂岩的年龄，表明导致新喀里多尼亚俯冲的汇聚旋回的开始。钙质超微化石、有孔虫、放射虫生物地层学和碳稳定同位素地层学将由一个合作研究小组进行。这些结果将给出西南太平洋生物、物理(磁)性质和碳循环演化的完整和按时间校准的框架。这样的数据集将是理解古近纪早期气候动力学的根本步骤，也将作为改进有关地球未来气候变化的模型的基础。

The Paleocene-Eocene world was dominated by warm conditions and the absence of permanent polar ice. A late Paleocene-early Eocene climate warming plummeted with the early Eocene climatic optimum (EECO; ~52-50 Ma), which was followed by a cooling trend over the middle-late Eocene that eventually drove the Earth to the present-day polar glacial condition. The early Paleogene long-term climate history was also punctuated by several transient (~10^3-10^5 yr) hyperthermal events. While the Northern Hemisphere is well represented by many outcropping and deep-sea magnetic-polarity calibrated records, the Southern Hemisphere is still lacking of an adequate number of continuous and well-calibrated stratigraphic records, especially the south Pacific, which had a fundamental role in the early Cenozoic heating transport. Given the high quality paleomagnetic results recently obtained by the late Paleocene-middle Eocene marine records cropping out in the South Island of New Zealand, here we propose a paleomagnetic and rock-magnetic study of the Pukemuri and Awheaiti Streams sections cropping out in Tora (Southeast Wairarapa, North Island, New Zealand) and of the Pain de Sucre, Sommet Khian, and Thonon sections cropping out in the Koumac-Gomen area (Grande-Terre Island, New Caledonia). These records will be integrated by magnetostratigraphic analyses of the DSDP Sites 206-210 (Leg 21, southwest Pacific Ocean). The sequence of magnetic polarity reversals from the target sections will be used for correlation with the international geomagnetic polarity time scale, determining a robust age-model of sedimentation. A well-established chronology for the Koumac-Gomen section will constrain the age of the accretionary complex of sediments indicating the onset of the convergence cycle leading to the obduction of New Caledonia. Calcareous nannofossil, foraminifera, radiolarian biostratigraphy and carbon stable isotope stratigraphy will be performed by a team of collaborating research groups. The results will give a complete and chronologically calibrated framework of the biological, physical (magnetic) properties, and carbon cycle evolution of the southwest Pacific. Such a dataset would be a fundamental step forward to understand the climate dynamics of the early Paleogene and it will also serve as basis to improve the models about the future climate changes of the Earth.