Ludfordian 中期 Lau 碳同位素偏移 (Lau CIE) 代表了显生宙中最大的正碳同位素偏移 (～9‰)，与许多海洋动物进化枝的生物多样性丧失相吻合。Lau CIE的两个主要解释是通过提高海洋生产力和保护驱动的缺氧扩大来增强有机碳埋藏。虽然这两种解释并不相互排斥，但 Lau CIE 的主要驱动力尚未受到限制。在这里，我们使用钡同位素（δ138巴) 沉积在整个 Lau CIE 的海相碳酸盐。我们的δ138巴来自科索夫部分（捷克共和国）的数据记录了与正向偏移相关的大的负偏移δ13C碳水化合物. 我们建议观察到的负转变δ138巴值低至-0.33‰可以最好地解释为由于在正常条件下的远洋重晶石溶解，同位素轻钡从更深的水域上涌。这一假设与钡浓度数据的结果以及硫酸盐质量平衡模型的结果一致，表明海水硫酸盐储层收缩，海水硫酸盐浓度从 Lau CIE 之前的几个 mM 范围降低到小于 100 μM。刘CIE。综上所述，证据表明两者之间存在强负相关δ138巴和δ13C碳水化合物表明浅水缺氧，而不是提高海洋生产力，是导致海水硫酸盐储层规模显着减小的 Lau CIE 的主要驱动因素。

"点击查看英文标题和摘要"

The mid-Ludfordian Lau carbon isotope excursion (Lau CIE) represents the largest positive carbon isotope excursion in the Phanerozoic (∼9‰), coincident with the biodiversity loss of many marine animal clades. Two main explanations for the Lau CIE are enhanced organic carbon burial via increased marine productivity and preservation-driven expansion of anoxia. While these two explanations are not mutually exclusive, the main driver of Lau CIE is yet to be constrained. Here, we resolve this longstanding debate using barium isotopes (δ138Ba) of marine carbonates deposited across the Lau CIE. Our δ138Ba data from the Kosov section (Czech Republic) record a large negative excursion in correlation to the positive shift in δ13Ccarb. We suggest that the observed negative shift in δ138Ba to values as low as −0.33‰ can be best interpreted as upwelling of isotopically light Ba from deeper waters due to pelagic barite dissolution under euxinic conditions. This hypothesis is consistent with results from barium concentration data as well as the results from the sulfate mass balance modeling that indicates a contraction in the seawater sulfate reservoir, with seawater sulfate concentrations decreasing from several mM ranges before the Lau CIE to less than 100 μM during Lau CIE. Taken together, evidence for a strong negative correlation between δ138Ba and δ13Ccarb suggests that shallow water anoxia, rather than enhanced marine productivity, was a primary driver of the Lau CIE that resulted in a notable decrease in the size of seawater sulfate reservoir.