Abstract: The secondary carbonate formed during the soil formation process (pedogenic carbonate) is a crucial material in
paleoclimate studies. In previous research, it has been widely used to reconstruct atmospheric CO₂ concentrations, paleoaltimetry, the evolution of regional paleovegetation (C₃, C₄ plants), precipitation, and temperature. However, like most other paleoclimate indicators, proxies based on pedogenic carbonate (such as stable carbon and oxygen isotopes, trace elements, etc.) are influenced by multiple climate factors, resulting in ambiguity. Therefore, obtaining reliable paleoenvironmental information requires the integration of multiple indicators. With the recent development of isotope testing methods, in addition to the traditional ¹⁸O/¹⁶O, triple oxygen isotope analysis (¹⁷O/¹⁶O) has been increasingly applied in paleoclimatology. Pedogenic carbonates inherit the oxygen isotope signal of soil water. Combined with the carbonate-clumped isotope temperature, the ¹⁷O anomaly of soil water can be reconstructed. The soil-water-Δ′¹⁷O is mainly controlled by the evaporation process, thus providing information about past humidity. This article provides a detailed introduction to the theoretical basis of pedogenic carbonate triple oxygen isotopes. It quantitatively discusses the impact of various climate factors on pedogenic carbonate triple oxygen isotopes using existing soil water triple oxygen isotope models.

Key words: triple oxygen isotopes, pedogenic carbonate, paleoclimate, relative humidity