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

我们在了解地球气候系统方面的进展将取决于我们能否将来自海洋、冰芯和陆地序列的高分辨率沉积档案联系起来，并在新的地球系统建模方法的背景下解释这些记录。世界上很少有地方可以做到足够详细和明确的海洋-冰-陆地联系。IODP和更广泛的钻探界面临的一个挑战是，从适当的地点以足够的时间分辨率确定和恢复海洋、冰层和陆地序列，以研究综合气候系统的过程。其中一个这样的区域是伊比利亚西南部边缘，尼克·沙克尔顿在那里证明了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，同一岩心的海底d18O信号与南极洲的温度记录相似。此外，由于塔古斯河的狭窄大陆架和邻近区域，陆地物质得以迅速运往葡萄牙近海的深海环境，从而提供了大气变化的记录，并将海洋和冰芯记录与欧洲陆地序列进行了对比。这是海洋中唯一一个明确证明了海洋-冰-陆地相互关系的地方。因此，通过JOIDES决议(JR)钻探，将伊比利亚边缘记录扩展到涵盖上更新世冰川-间冰期旋回的全部范围是非常可取的。为此，以英国为首的一个由16个支持者组成的国际小组向IODP提交了771-FULL提案。科学指导和评估小组(SSEP)很好地接受并审查了这项建议，但IODP现场调查小组(SSP)发现了地震质量的主要不足之处：“专家小组对提交的数据的适当性提出了几点关注，无论是对目标进行适当的成像，还是关于场地位置。专家小组还讨论了是否需要两条高分辨率测线，并认为存在物质输运沉积(MTDS)或断层间距较近的地方理应拥有这两条高分辨率测线。还提出了与伊比利亚西南边缘现代水文学和沉积过程有关的几个“独立”科学目标，以及用于重建过去深水循环变化的古海洋学指标的校准。这一增值科学将有效利用船舶时间，为下岩心记录的解释做出根本性贡献。

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 Nick Shackleton 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:"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 project requests 20 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 make a fundamental contribution to the interpretation of downcore records.