The evolution of the global carbon and silicon cycles is thought to have contributed to the long-term stability of Earth’s climate^1,2,3. Many questions remain, however, regarding the feedback mechanisms at play, and there are limited quantitative constraints on the sources and sinks of these elements in Earth’s surface environments^{4,5,6,7,8,9,10,11,12}. Here we argue that the lithium-isotope record can be used to track the processes controlling the long-term carbon and silicon cycles. By analysing more than 600 shallow-water marine carbonate samples from more than 100 stratigraphic units, we construct a new carbonate-based lithium-isotope record spanning the past 3 billion years. The data suggest an increase in the carbonate lithium-isotope values over time, which we propose was driven by long-term changes in the lithium-isotopic conditions of sea water, rather than by changes in the sedimentary alterations of older samples. Using a mass-balance modelling approach, we propose that the observed trend in lithium-isotope values reflects a transition from Precambrian carbon and silicon cycles to those characteristic of the modern. We speculate that this transition was linked to a gradual shift to a biologically controlled marine silicon cycle and the evolutionary radiation of land plants^13,14.

全球碳和硅循环的演变被认为有助于地球气候的长期稳定^1,2,3。然而，关于反馈机制的作用仍有许多问题，而且地球表面环境中这些元素的源和汇的数量限制有限^{4,5,6,7,8,9,10,11,12}. 在这里，我们认为锂同位素记录可用于追踪控制长期碳和硅循环的过程。通过分析来自 100 多个地层单元的 600 多个浅水海相碳酸盐岩样品，我们构建了跨越过去 30 亿年的新碳酸盐基锂同位素记录。数据表明碳酸盐锂同位素值随时间增加，我们认为这是由海水锂同位素条件的长期变化驱动的，而不是由旧样品的沉积蚀变变化驱动的。使用质量平衡建模方法，我们提出观察到的锂同位素值趋势反映了从前寒武纪碳和硅循环到现代特征的转变。^13,14。