A simple process-based model of the Li, Mg, Ca, Sr and alkalinity cycles in the ocean has been developed with the aim of better understanding the information contained in the evolution of Cenozoic seawater chemistry. In the model, changes in seawater chemistry are forced by changing climatic (temperature) and tectonic (ocean crust accretion rate and continental weatherability) conditions. These drive time-varying element and isotope fluxes from continental and seafloor weathering, mid-ocean ridge hydrothermal systems and sedimentation. Inverse modelling reveals that a range of model parameter values can simultaneously reproduce the key features of the Cenozoic history of seawater chemistry for all species considered. In addition to Cenozoic cooling, a decrease in the rate of ocean crust accretion and/or an increase in continental weatherability are required to fit the data. However, paleoseawater compositions do not allow the relative roles of these tectonic forcings to be determined. While other processes (e.g., changes in surface lithology) may have played a role in generating the observed variations in seawater chemical and isotopic composition, they are not required to explain the general tends in the data. The increase in Mg/Ca over the Cenozoic in acceptable models is largely driven by a decrease in the Ca/alkalinity of the net continental, diagenetic and hydrothermal fluxes, and not by an increase in the Ca/alkalinity of the carbonate mineral sink. Thus, the increase in seawater Mg/Ca over the Cenozoic is readily explained without any decrease in dolomite formation. Notably, all acceptable models have a stronger temperaturedependence of seafloor than continental weathering. This means that climatically driven changes in chemical fluxes in the model come dominantly from seafloor, not continental, weathering.

为了更好地理解新生代海水化学演化所包含的信息，已经开发了一个基于过程的简单的海洋中锂、镁、钙、锶和碱度循环的模型。在该模型中，海水化学的变化是受气候（温度）和构造（海洋地壳增生率和大陆耐候性）条件变化的影响。这些驱动来自大陆和海底风化、大洋中脊热液系统和沉积的时变元素和同位素通量。逆向建模表明，一系列模型参数值可以同时再现所有物种新生代海水化学历史的关键特征。除了新生代降温，为了拟合数据，需要降低洋壳的增生率和/或增加大陆的耐候性。然而，古海水成分不允许确定这些构造强迫的相对作用。虽然其他过程（例如，地表岩性变化）可能在产生所观察到的海水化学和同位素组成变化方面发挥了作用，但它们不需要解释数据中的一般趋势。在可接受的模型中，新生代 Mg/Ca 的增加主要是由于净大陆、成岩和热液通量的 Ca/碱度降低，而不是碳酸盐矿物汇的 Ca/碱度增加。因此，很容易解释新生代海水 Mg/Ca 的增加，而白云石形成没有任何减少。尤其，所有可接受的模型都比大陆风化对海底温度的依赖性更强。这意味着模型中化学通量的气候驱动变化主要来自海底，而不是大陆风化。