The accuracy of ages produced by the U-Pb speleothem chronometer is influenced by initial disequilibrium effects resulting from weathering and transit of water through the epikarst. If some residual disequilibrium remains at the time of measurement, corrections can be made. However, once the system reaches equilibrium, the initial state has to be estimated thus propagating significant uncertainty into the age calculation. As an alternative approach, here we explore the possibility of calculating [²³⁴U/²³⁸U]_i initial values by forcing concordance in the ²³⁸U to ²⁰⁶Pb and ²³⁵U to ²⁰⁷ Pb decay schemes.

Whether this method can be successfully implemented relies heavily on the quality of the linear regression enacted, particularly with respect to the ²³⁵U-²⁰⁷ Pb decay scheme. We therefore also explore the effect of ²⁰⁸Pb-based normalisation in order to optimise isochron construction. An unexpected consequence of this analysis is the observation that ²⁰⁸Pb/²⁰⁴Pb ratios may aid in the identification of heterogeneous initial Pb isotopic compositions in speleothems. Both methods have the potential to generate improved isochron fits which ultimately produce improved disequilibrium corrected speleothem ages. Initial disequilibrium values obtained in this way can be applied to other samples where disequilibrium information is unavailable.

U-Pb潜能计时码表产生的年龄精度受风化和水通过表层岩溶的初始不平衡影响。如果在测量时残留一些不平衡，则可以进行校正。但是，一旦系统达到平衡，就必须估计初始状态，从而将很大的不确定性传播到年龄计算中。作为一种替代方法，这里我们探索通过在²³⁸ U至²⁰⁶ Pb和²³⁵ U至²⁰⁷  Pb衰减方案中强制采用一致来计算[ ²³⁴ U / ²³⁸ U] _i初始值的可能性。

这种方法能否成功实施，在很大程度上取决于所制定的线性回归的质量，尤其是在²³⁵ U- ²⁰⁷  Pb衰减方案方面。因此，我们还探索了基于²⁰⁸ Pb的归一化的效果，以优化等时线构造。该分析的意外结果是观察到²⁰⁸ Pb / ²⁰⁴铅的比率可能有助于鉴定脾肿物中异质的初始铅同位素组成。两种方法都有可能产生改进的等时拟合，最终产生改进的不平衡校正的脾​​动脉年龄。以这种方式获得的初始不平衡值可以应用于其他不平衡信息不可用的样本。