Assessing the fidelity of conodont apatite for seawater ⁸⁷Sr/⁸⁶Sr reconstruction in the context of the Guadalupian-Lopingian transition

We provide high-resolution conodont-based ⁸⁷Sr/⁸⁶Sr data from the Fengshan section (South China), the Standard Auxiliary Boundary Stratotype (SABS) for the base of the Lopingian, and compare them with bulk carbonate samples employing both weak-acid and sequential leaching protocols to explicitly assess the effects of diagenetic alteration and Sr loss. Our results demonstrate that bulk carbonate archives, even after sequential leaching, commonly yield more radiogenic and more variable ⁸⁷Sr/⁸⁶Sr values than coeval conodont apatite, highlighting diagenetic influences on bulk carbonates. In contrast, conodont-derived ⁸⁷Sr/⁸⁶Sr values show reduced scatter and closely match independently constrained brachiopod records, supporting their reliability as a conservative archive of seawater ⁸⁷Sr/⁸⁶Sr signal.