IODP Survey of the "Shackleton Sites" on the Southwest Iberian Margin

我们对地球气候系统理解的进步将依赖于我们将来自海洋、冰芯和陆地序列的高分辨率沉积档案联系起来的能力，以及在新的地球系统建模方法的背景下解释这些记录的能力。世界上很少有地方能够充分详细和明确地了解海洋-冰-陆地的联系。IODP和更广泛的钻井界面临的一个挑战是，在适当的位置和适当的时间分辨率下，识别和恢复海洋、冰和陆地序列，以研究综合气候系统的过程。其中一个这样的地区是伊比利亚西南边缘，在那里已经证明，表面氧同位素记录可以精确地与格陵兰冰芯的温度变化（即d18O）相关联。相比之下，同一地核的底栖生物d18O信号与南极洲的温度记录相似。此外，狭窄的大陆架和靠近塔霍河导致陆地物质迅速输送到葡萄牙附近的深海环境，从而提供了大气变化的记录，并允许将海洋和冰芯记录与欧洲陆地序列进行对比。这是海洋中唯一一个这样的海洋-冰-陆地相关性得到明确证明的地方。因此，利用JOIDES分辨率（JR）钻井扩展伊比利亚边缘记录，以涵盖上新世-更新世冰期-间冰期旋回的全部范围是非常必要的。为此，以英国为首的一个由16名支持者组成的国际小组向IODP提交了771-Full提案。该提案得到了科学指导和评估小组（SSEP）的良好接受和审查，但IODP现场调查小组（SSP）确定了地震数据质量的主要不足之处：“小组对提交的数据的适用性提出了几个担忧，包括其适当性，既要对目标进行适当成像，也要考虑到现场位置。小组还讨论了2条高分辨率线路的必要性，并认为存在大块搬运沉积物（MTDs）或紧密断层的地方值得这2条高分辨率线路。“该提案要求25天的航行时间来收集满足SSP要求和建议所需的必要地震和沉积物数据。还提出了几个“独立”的科学目标，涉及伊比利亚西南边缘的现代水文和沉积过程，以及用于重建过去深水环流变化的古海洋学代用物的校准。这种增值科学将有效利用船舶时间，并提供解释由IODP获得的下核记录所需的关键信息。

Advances in our understanding of the Earth's climate system will rely on our ability to link high-resolution sedimentary archives from the oceans, ice-cores and terrestrial sequences, and to interpret these records in the context of novel Earth system modeling approaches. Few places exist in the world where sufficiently detailed and unambiguous marine-ice-terrestrial linkages are possible. One challenge for IODP, and the broader drilling community in general, is to identify and recover marine, ice and terrestrial sequences from appropriate locations and with adequate temporal resolution to study processes of the integrated climate system. One such region is the southwest Iberian Margin where it has been demonstrated that the surface oxygen isotopic record could be correlated precisely to temperature variations (i.e., d18O) in Greenland ice cores. By comparison, the benthic d18O signal in the same core resembled the temperature record from Antarctica. Moreover, the narrow continental shelf and proximity of the Tagus River results in the rapid delivery of terrestrial material to the deep-sea environment off Portugal, thereby providing a record of atmospheric changes and permitting correlation of marine and ice core records to European terrestrial sequences. This is the only place in the ocean where such marine-ice-terrestrial correlations have been demonstrated unambiguously. It is therefore highly desirable to extend the Iberian Margin record to encompass the full range of Plio-Pleistocene glacial-interglacial cycles by drilling with the JOIDES Resolution (JR).Towards this end, Proposal 771-Full was submitted to IODP by an international group of 16 proponents led by the UK. The proposal was well received and reviewed by the Science Steering and Evaluation Panel (SSEP), but the IODP Site Survey Panel (SSP) identified major inadequacies in the quality of the seismic data:"The panel raised several concerns on the suitability of the submitted data with regard to its appropriateness, both to image the target properly and with regard to the site location. The panel also discussed the need for 2 high-resolution lines and considered that places where Mass Transport Deposits (MTDs) or closely spaced faults were present deserved these 2 high-resolution lines."This proposal requests 25 days of ship time to collect the necessary seismic and sediment data needed to meet the SSP requirements and recommendations. Several "stand-alone" scientific objectives are also proposed related to the modern hydrography and sedimentary processes on the southwest Iberian Margin, and calibration of palaeoceanographic proxies used for reconstructing past changes in deep-water circulation. This value-added science will make effective use of ship time and contribute key information needed to interpret the downcore records to be obtained by IODP.