Stable isotope ratios and abundances of selected foraminifera taxa from ODP Leg 172 sites

This data report describes the results of post-Leg 172 sampling of Sites 1054, 1055, and 1063 for two purposes: to investigate the climatic significance of red-colored intervals in the hemipelagic sediments cored during Leg 172 and to better understand the stratigraphy and chronology of Carolina Slope Sites 1054 and 1055. Gravity cores collected from the Carolina Slope on site survey cruise Knorr 140/2 show very high rates of sedimentation during the Holocene and lower rates during the last glacial maximum (LGM). Because of the high rates, many of the sediments in the recovered cores never reached the LGM. In other cores, it is possible that deglacial oscillations have been mistaken for the LGM. Although radiocarbon dating could solve that problem, some of the gravity cores are at or very close to the Ocean Drilling Program (ODP) sites, and it is useful to compare the isotope stratigraphies among them before proceeding with dating. Furthermore, some of the site survey cores have red-colored intervals and others do not, even though there is some indication they are time equivalent. Either the stratigraphy is wrong, diagenesis has affected the color of the sediment, or red sediment is carried to some sites but not to others that differ in depth by only a few hundred meters.

本数据报告阐述了第172航次后对1054、1055及1063站位开展采样工作的成果，本次采样旨在达成两项核心目标：一是探究第172航次所获半远洋沉积岩心中红色层段的气候指示意义；二是进一步明晰卡罗莱纳陆坡1054与1055站位的地层学与年代学特征。通过Knorr号140/2航次现场调查自卡罗莱纳陆坡采集的重力活塞岩心数据显示，全新世时期沉积速率极高，而末次冰盛期（Last Glacial Maximum, LGM）沉积速率显著偏低。受较高沉积速率影响，所获岩心中的多数沉积物从未抵达末次冰盛期地层。在其余岩心中，冰消期振荡信号有可能被误判为末次冰盛期沉积产物。尽管放射性碳定年技术可解决该识别难题，但部分重力活塞岩心恰好位于或紧邻海洋钻探计划（Ocean Drilling Program, ODP）站位，因此在启动定年工作前，先对各岩心的同位素地层学特征开展对比分析具有重要实用价值。此外，部分现场调查岩心存在红色层段，其余则无此类特征；尽管已有迹象表明这些岩心的沉积时代大致相当。该现象可能存在三种成因：地层划分存在误差、成岩作用改变了沉积物颜色，或是红色沉积物仅被搬运至部分站位，而对仅相距数百米的相邻站位却未产生影响。