Carbon isotopic fractionation of alkenones and Gephyrocapsa coccoliths over the Late Quaternary (Marine Isotope Stages 12 to 9) glacial-interglacial cycles at the western tropical Atlantic

Here we present εp measured on natural fossil samples across the glacial-interglacial (G-I) MIS 12 to MIS 9 (454-334 ka) interval at the western tropical Atlantic Ocean Drilling Program Site 925 together with a set of organic and inorganic geochemical, micropaleontological and morphometrical data from Gephyrocapsa coccolith on the same samples. Primary productivity and export production, potentially triggered by shifting growth rates and light level conditions, and the changes in Gephyrocapsa cellular dimensions are controlled by either proxies or direct measurements, allowing to parse out the load of non-CO2 effects on εp. We also determined oxygen and carbon stable isotope vital effects in the near monogeneric separated Gephyrocapsa coccoliths (respectively δ18O Gephyrocapsa-T. sacculifer and εcoccolith)

本研究报道了热带大西洋西部深海钻探计划（Ocean Drilling Program，ODP）925站位在454~334 ka（距今45.4万至33.4万年，对应冰期-间冰期（G-I）海洋同位素阶段（Marine Isotope Stage，MIS）12至MIS 9时段）的天然化石样品所测得的εp值，以及同一样品中桥石藻属（Gephyrocapsa）颗石的一系列有机、无机地球化学、微古生物学及形态计量学数据。潜在由生长速率与光照条件变化驱动的初级生产力及输出生产力，以及桥石藻细胞尺寸的改变，可通过代用指标或直接测量进行约束，由此得以厘清非CO₂效应对εp的影响权重。本研究还测定了近乎单属分离的桥石藻颗石中的氧、碳稳定同位素生命效应，二者分别对应桥石藻与T. sacculifer的δ¹⁸O差值，以及颗石εcoccolith值。