Boron, carbonate carbon and oxygen isotope analyses of samples from the Yangtze Platform (China), Congo craton (Namibia), and Karatau microcontinent (Kazakhstan) of the Marinoan glaciation

Boron isotope patterns preserved in cap carbonates deposited in the aftermath of the younger Cryogenian (Marinoan, ca. 635 Ma) glaciation confirm a temporary ocean acidification event on the continental margin of the southern Congo craton, Namibia. To test the significance of this acidification event and reconstruct Earth's global seawater pH states at the Cryogenian-Ediacaran transition, we present a new boron isotope data set recorded in cap carbonates deposited on the Yangtze Platform in south China and on the Karatau microcontinent in Kazakhstan. Our compiled d11B data reveal similar ocean pH patterns for all investigated cratons and confirm the presence of a global and synchronous ocean acidification event during the Marinoan deglacial period, compatible with elevated postglacial pCO2 concentrations. Differences in the details of the ocean acidification event point to regional distinctions in the buffering capacity of Ediacaran seawater.保存在新元古代成冰纪晚期（马里诺冰期，约6.35亿年）冰期之后沉积的盖帽碳酸盐岩（cap carbonates）中的硼同位素（boron isotope）分布特征，证实了纳米比亚南部刚果克拉通（Congo craton）大陆边缘曾发生过一次短暂的海洋酸化事件。为验证此次酸化事件的科学意义，并重建成冰纪-埃迪卡拉纪（Cryogenian-Ediacaran）过渡时期全球海水pH状态，本研究报道了一组新的硼同位素数据集，其采集自中国南方扬子地台（Yangtze Platform）与哈萨克斯坦卡拉套微大陆（Karatau microcontinent）上沉积的盖帽碳酸盐岩。本研究整合的δ¹¹B比值数据显示，所有被研究克拉通均呈现出相似的海洋pH变化模式，证实了马里诺冰期冰消期存在一次全球性同步的海洋酸化事件，该事件与冰期后升高的二氧化碳分压（pCO₂）浓度相吻合。此次海洋酸化事件在细节上的差异，则表明埃迪卡拉纪海水的缓冲能力存在区域差异。