The deep‐sea sedimentary record of Ocean Drilling Program Site 690 (Weddell Sea) has figured prominently in the study of an ancient (~56 Ma) global warming event referred to as the Paleocene‐Eocene Thermal Maximum (PETM). Yet discrepancies in the timing, amplitude, and structure of the isotopic excursions marking the PETM exist between the bulk‐carbonate and planktic foraminifer stable isotope (δ¹³C and δ¹⁸O) records of this reference section. A recent study invoked size‐dependent sediment mixing (SDSM) to reconcile the discrepancies between these parallel δ¹³C records. Here we report supplementary stable isotope data compiled from size‐segregated planktic foraminifer shells that further elucidate the effects of SDSM on the Site 690 PETM section. Our records reveal a stratigraphic sequence where the carbon (CIE) and oxygen (OIE) isotope excursions marking the onset of PETM conditions are first registered by larger shells, confirming that smaller‐sized pre‐CIE shells have been more intensely mixed and preferentially displaced up‐section into the overlying CIE interval. The size‐dependent manner in which the CIE and OIE are recorded by asymbiotic subbotinids indicates that the transitory loss of size‐dependent δ¹³C signatures in photosymbiotic taxa (acarininids) at Site 690 is an artifact of SDSM. Synthetic bulk‐carbonate δ¹³C records generated with two end‐member (pre‐CIE versus CIE materials) sediment‐mixing curves readily reproduce the series of “steps” seen in published bulk‐carbonate δ¹³C records of the CIE, suggesting that these fine‐scale features may also be artifacts of SDSM and varying rates of carbonate sedimentation.

中文翻译：

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延迟，差异和变形：ODP站点690（Weddell Sea）的大小相关沉积物混合和古新世始新世热最大值的深海记录

海洋钻探计划站点690（韦德尔海）的深海沉积记录在一项古老的（〜56 Ma）全球变暖事件（古新世-始新世最大热值（PETM））的研究中占有重要地位。然而，在所述定时，振幅和同位素游览标记PETM的结构差异的本体-碳酸酯和浮游有孔虫稳定同位素之间（δ存在¹³ C和δ ¹⁸ O）这个参考部分的记录。最近的一项研究调用尺寸相关沉积物混合（SDSM）调和这些平行δ之间的差异¹³C记录。在这里，我们报告了根据尺寸分隔的板状有孔虫壳汇编的补充稳定同位素数据，这些数据进一步阐明了SDSM对Site 690 PETM剖面的影响。我们的记录揭示了一个地层学层序，其中标志着PETM条件发生的碳（CIE）和氧（OIE）同位素偏移首先被较大的壳层记录，这证实较小尺寸的CIE之前的壳层已经更强烈地混合并优先向上偏移-进入上层CIE区间。其中CIE和OIE由非共生subbotinids记录的大小依赖的方式表明，依赖于大小的δ的瞬态损耗¹³在photosymbiotic类群（acarininids）在站点690Ç签名是SDSM的人工制品。合成的散装-碳酸酯δ ¹³Ç记录了与两个端构件产生（预CIE与CIE材料）沉淀混合曲线容易地再现一系列已公开的散装碳酸盐δ看到“台阶” ¹³的CIE的Ç记录，表明这些精细尺度特征可也可能是SDSM的产物和碳酸盐沉积速率的变化。