Soru

In speleothem paleoclimatology, the isotopic composition of calcite stalagmites provides high-resolution continental climate records. The ratio of oxygen-18 to oxygen-16 ($\delta^{18}\text{O}$) in cave calcite has historically been interpreted as a direct proxy for regional paleotemperature, predicated on the temperature-dependent equilibrium fractionation during calcite precipitation. However, recent hydrochemical analyses in semi-arid karst systems indicate that kinetic fractionation during rapid drip-water degassing often obscures this thermodynamic relationship. When drip rates decrease—such as during prolonged droughts—carbon dioxide outgasses rapidly from the thin water film covering the stalagmite tip prior to calcite precipitation. This kinetic outgassing preferentially removes lighter carbon-12 and oxygen-16 isotopes into the cave atmosphere, driving both $\delta^{18}\text{O}$ and $\delta^{13}\text{C}$ in the precipitated calcite toward markedly heavier values, entirely independent of ambient exterior temperature shifts. Consequently, in water-stressed regimes, simultaneous isotopic enrichment in $\delta^{18}\text{O}$ and $\delta^{13}\text{C}$ serves primarily as an indicator of diminished drip frequency and heightened cave ventilation rather than cooler surface temperatures. Moreover, because carbon isotopes are also influenced by overlying soil microbial respiration and vegetation density (which diminish during arid intervals and decrease light carbon inputs from decaying organic matter), uncoupling hydrologic kinetic effects from biological soil processes requires measuring auxiliary geochemical tracers, such as strontium-to-calcium ($\text{Sr}/\text{Ca}$) ratios resulting from prior calcite precipitation along the infiltration pathway.

Based on the passage, which of the following statements can be logically inferred? (Select all that apply)