The late Cambrian Steptoean positive carbon isotope excursion (SPICE) represents a major perturbation to the global carbon cycle and was associated with trilobite extinctions and expansion of anoxic and/or euxinic water masses during episodes of eustatic sea-level change. We present a new Re-Os age together with Os and Nd isotope stratigraphy and major- and trace-element data from the Alum Shale Formation (Scania, Sweden). The Re-Os age of 494.6 ± 2.9 Ma is from the interval of peak δ13Corg values, providing the first radiometric age constraint for this Cambrian carbon isotope excursion, interpreted as a possible pre-Mesozoic ocean anoxia event, and the timing of biomere-level extinctions. The Os isotope chemostratigraphic profile can be explained by an increase in terrigenous weathering prior to the SPICE, potentially driven by sea-level fall, and in agreement with enhanced nutrient supply, primary productivity, and organic matter burial as the driver of the SPICE event. Post-SPICE, the Os isotopes become increasingly unradiogenic; however, invariant εNd(t) values argue against a change in provenance and instead support a decrease in the continental weathering flux, possibly related to eustatic sea-level rise.

中文翻译：

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寒武纪 SPICE 事件的 Re-Os 年代学：从放射性同位素对euxinia 和增强大陆风化的洞察

晚寒武纪 Steptoean 正碳同位素偏移 (SPICE) 代表了对全球碳循环的主要扰动，并且与海平面变化期间三叶虫灭绝和缺氧和/或常温水团的扩张有关。我们提出了一个新的 Re-Os 年龄以及 Os 和 Nd 同位素地层学以及来自明矾页岩组（斯堪尼亚，瑞典）的主量和微量元素数据。Re-Os 年龄 494.6 ± 2.9 Ma 来自 δ13Corg 峰值区间，为这次寒武纪碳同位素偏移提供了第一个辐射年龄限制，被解释为可能的中生代前海洋缺氧事件，以及生物群水平的时间灭绝。Os同位素化学地层剖面可以用SPICE之前的陆源风化增加来解释，这可能是由海平面下降驱动的，并且与作为 SPICE 事件驱动因素的增强的养分供应、初级生产力和有机物质掩埋一致。在 SPICE 之后，Os 同位素变得越来越不具放射性；然而，不变的 εNd(t) 值反对出处的变化，而是支持大陆风化通量的减少，这可能与海平面上升有关。