Ubiquitous karst hydrological control on speleothem oxygen isotope variability in a global study

Karst hydrology exerts a key influence on oxygen isotopic compositions in cave speleothems, according to a global analysis of in-cave differences. The effect of flowpaths through fractures could affect speleothem-based reconstructions of past hydroclimates. Speleothem oxygen isotopic (delta O-18) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem delta O-18 to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem delta O-18 values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater delta O-18 variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem delta O-18 records.

Automated summary

Karst hydrology has a significant impact on the oxygen isotopic compositions of cave speleothems, and global analysis suggests that inconsistencies in speleothem-based reconstructions of past hydroclimates are common worldwide. The influence of fractures on flowpaths is identified as the primary driver of within-cave speleothem and dripwater oxygen isotopic variability.