In the Precambrian, reverse weathering—a process consuming oceanic silica, metal cations and alkalinity to form marine clays—was a key control of the long-term carbon cycle. However, the appearance of marine silicifiers decreased the importance of this process in regulating climate in the Phanerozoic eon. Here, we present seawater lithium and strontium isotope records derived from bulk carbonates and fossil brachiopods spanning the Permian to Early Triassic, an interval of pronounced climatic fluctuations and widespread extinctions. We show that the lithium isotope composition of seawater remained constant for most of the Permian until a sharp decrease in the Late Permian (~254 Myr ago) with low seawater Li isotope values (~10‰) persisting throughout the Early Triassic. Based on box modelling, changes in chemical weathering and hydrothermal fluxes are unable to explain the abrupt decline in seawater Li isotopes. Rather, increased lithium output fluxes through enhanced reverse weathering are required to produce the low Li isotope values of the Late Permian and Early Triassic (253–247 Myr ago). Increased reverse weathering rates could explain the failure of chemical weathering to draw down atmospheric CO₂ levels during the Early Triassic, leading to protracted biotic recovery from the Permian–Triassic mass extinction.

在前寒武纪，逆风化——一个消耗海洋二氧化硅、金属阳离子和碱度形成海洋粘土的过程——是长期碳循环的关键控制因素。然而，海洋硅化物的出现降低了这一过程在显生宙调节气候中的重要性。在这里，我们展示了从二叠纪到早三叠世的散装碳酸盐和腕足动物化石中提取的海水锂和锶同位素记录，这是一段明显的气候波动和广泛灭绝的时期。我们表明，在二叠纪的大部分时间里，海水的锂同位素组成保持不变，直到二叠纪晚期（~254 Myr 前）急剧下降，海水锂同位素值低（~10‰）在整个早三叠世持续存在。基于盒子建模，化学风化和热液通量的变化无法解释海水锂同位素的突然下降。相反，需要通过增强的反向风化来增加锂输出通量，以产生晚二叠世和早三叠世（253-247 Myr 前）的低 Li 同位素值。增加的逆风化率可以解释化学风化未能吸收大气中的二氧化碳_{早三叠世期间的2 个}水平，导致从二叠纪-三叠纪大规模灭绝中长时间的生物恢复。