A global Ediacaran-Cambrian Age Model of 130 geological successions, with radiometric ages (zircon U-Pb CA-ID-TIMS), carbon (δ13Ccarb) and strontium (87Sr/86Sr) isotope data (NERC Grant NE/T008458/1)

We present new age models for the Ediacaran-Cambrian which lacks a robust global temporal framework. This interval marks the radiation of animals, but there are major uncertainties in the evolutionary dynamics of this critical radiation and its relationship to changes in palaeoenvironmental changes. Here we present global data from 130 successions that enable us to create four new possible global age models (A to D) for the interval 551–517 million years ago (Ma). These models comprise composite carbonate carbon isotope (δ13Ccarb) curves, which are anchored to radiometric ages and consistent with strontium isotope chemostratigraphy, and are used to calibrate metazoan distribution in space and time. These models differ most prominently in the temporal position of the basal Cambrian negative δ13Ccarb excursion (BACE). Two age models (A and B) place the BACE within the Ediacaran, and yield an age of ~538.8 Ma for the Ediacaran-Cambrian boundary; however models C and D appear to be the most parsimonious and may support a recalibration of the boundary age by up to 3 Myr younger. All age models reveal a previously underappreciated degree of variability in the terminal Ediacaran, incorporating notable positive and negative excursions that precede the BACE. Nothwithstanding remaining uncertainties in chemostratigraphic correlation, all models support a pre-BACE first appearance of Cambrian-type shelly fossils in Siberia and possibly South China, and show that the Ediacaran-Cambrian transition was a protracted interval represented by a series of successive radiations. Data were compiled by Fred Bowyer, with support from Andrey Yu. Zhuravlev, Rachel Wood, Maoyan Zhu, Graham Shields, Ying Zhou, Chuang Yang, Simon Poulton, Dan Condon, Andrew Curtis.

本研究提出适用于埃迪卡拉纪-寒武纪时期的新模型，该时期缺乏一个稳健的全球时间框架。这一时期标志着动物的辐射演化，但关于这一关键辐射的演化动态及其与古环境变化的关联存在重大不确定性。在此，我们呈现了130个连续地层全球数据，这些数据使我们能够为距今约5.51亿至5.17亿年前（百万年）的时段构建四个新的可能全球年龄模型（A至D）。这些模型包括与放射性年龄锚定的复合碳酸盐碳同位素（δ13Ccarb）曲线，与锶同位素化学地层学一致，并用于校准无脊椎动物在时空中的分布。这些模型在寒武纪基础层负δ13Ccarb突跃（BACE）的时间位置上最为显著不同。模型A和B将BACE定位在埃迪卡拉纪内，并得出埃迪卡拉纪-寒武纪边界约538.8百万年的年龄；然而，模型C和D看起来更为简约，可能支持将边界年龄重新校准至年轻约30万年。所有年龄模型均揭示了之前未被充分认识的埃迪卡拉纪末期变化程度，包括在BACE之前发生的显著的正负突跃。尽管在化学地层学相关性方面仍存在不确定性，但所有模型均支持在BACE之前西伯利亚和可能的中国南部首次出现寒武纪型壳体化石，并表明埃迪卡拉纪-寒武纪过渡是一个漫长的时期，由一系列连续的辐射事件所代表。数据由Fred Bowyer汇编，在Andrey Yu. Zhuravlev、Rachel Wood、Maoyan Zhu、Graham Shields、Ying Zhou、Chuang Yang、Simon Poulton、Dan Condon和Andrew Curtis的支持下完成。