Oxygen and carbon isotopic analysis in terrestrial snail shells: from methodology to interpretations

Mollusc shells are among the most common fossil remains in Quaternary sediments. Classical palaeoenvironmental reconstructions are based on mollusc assemblages and the ecological preferences of the species. These approaches can be complemented by stable isotope analysis, which adds information on the environmental conditions under which the organisms lived. Oxygen isotope values in land snail shells are mainly used to estimate the isotopic composition of precipitation and can also provide temperature estimates. The carbon isotope values reflect the diet and the dominant vegetation type (e.g., C3 vs. C4 plants) in their surroundings. Despite decades of study, the processes controlling the incorporation of stable oxygen and carbon isotopes into land snail shells are still not fully understood, especially the relative influence of environmental versus biological factors. This understanding is essential for an accurate interpretation of the isotopic data. This paper reviews research on stable isotope analysis of land snail shells. It summarises methodologies, sampling strategies, and sample preparation techniques for oxygen and carbon isotope measurements. It also discusses applications of isotopic data in palaeoclimatic and palaeoenvironmental reconstructions using modern and fossil shells, highlights interpretative limitations, and examines biological and environmental factors that influence isotopic signatures.