Öate Cretaceous to early Paleogene nutrient and paleoproductivity records of ODP Leg 171 sites@en

We evaluate phosphorus (P) and biogenic barium (bio-Ba) as nutrient burial and export productivity indicators for the Late Cretaceous and early Paleogene, combining these with calcium carbonate (CaCO3), organic carbon (C), and bulk CaCO3 C isotopes (d13C). Sample ages span 36-71 Ma (~1 sample/0.5 m.y.) for a depth transect of sites in the western North Atlantic (Blake Nose, Ocean Drilling Program Leg 171B, Sites 1052, 1051, and 1050). We use a multitracer approach including redox conditions to investigate export productivity surrounding the global Paleocene d13C maximum (~57 Ma). Reducing conditions render most of the bio-Ba record not useful for export productivity interpretations. P and organic C records indicate that regional nutrient and organic C burial were high at ~61 and ~69 Ma, and low during the Paleocene d13C maximum, a time of proposed global high relative organic C burial. Observed organic C burial changes at Blake Nose cannot explain this C isotope excursion.本研究以磷（P）与生源钡（bio-Ba）作为白垩纪晚期与古近纪早期的营养盐埋藏及输出生产力指标，结合碳酸钙（CaCO₃）、有机碳（C）以及总碳酸钙碳同位素（δ¹³C）开展分析。样品年龄跨度为36至71百万年（约每0.5百万年采集1个样品），采样覆盖西北大西洋布雷克海岭（Blake Nose）大洋钻探计划（Ocean Drilling Program）第171B航次的1052、1051及1050站位的深度断面。我们采用包含氧化还原条件在内的多示踪剂方法，探究古新世全球碳同位素最大值事件（~57 Ma）前后的输出生产力状况。还原环境导致绝大多数生源钡记录无法用于输出生产力的解译。磷与有机碳记录显示，区域营养盐与有机碳埋藏在约61百万年和约69百万年时处于高位，而在古新世全球碳同位素最大值事件期间处于低位——该事件被认为是全球相对有机碳埋藏量较高的时期。布雷克海岭观测到的有机碳埋藏变化无法解释此次碳同位素偏移事件。