High-resolution trace-element records in land snail shells as proxies for weather-scale environmental variability

Land snail shells represent a rapidly accumulating, high-resolution terrestrial archive with unique potential for reconstructing past weather-scale environmental changes. To date, studies relied exclusively on the oxygen isotopes in shells, leaving the potential of other proxies (i.e., trace-element ratios) largely unexplored. Here, we present the first in-situ, high-resolution profiles of Na/Ca, Mg/Ca, Sr/Ca, Ba/Ca, and Mn/Ca from modern Cathaica fasciola shells collected from the Chinese Loess Plateau. Na/Ca, Sr/Ca, and Ba/Ca exhibit consistent covariation, likely reflecting shared lattice-substitution behavior and transport pathways, whereas Mg/Ca and Mn/Ca may be more influenced by organic mediation and local calcification dynamics. Trace-element incorporation may be jointly controlled by biological processes and environmental forcing, including growth rate, calcification dynamics and hydro-chemical variability. Weather-scale rainfall events may be associated with transient shifts in soil-solution chemistry that are reflected in the shells as short-term excursions. The frequency of trace-element excursions broadly matches the counts of rainfall occurrence, suggesting a possible link between shell geochemistry and weather-scale hydrological variability. During a “once-in-a-millennium” rainstorm, snail shell Mg/Ca and Mn/Ca exhibited a pronounced spike and a sustained anomaly, respectively, highlighting their sensitivity to extreme events, whereas Na/Ca, Sr/Ca, and Ba/Ca show more reproducible covariation among samples and may be better suited for reconstructing the frequency of weather-scale rainfall event. These results provide preliminary evidence that trace-element in land snail shells may hold potential for tracking environmental variability at weather timescales, though the underlying mechanisms are complex and warrant further study.