Clumped and stable isotopes of land snail shells on the Chinese Loess Plateau and their climatic implications

Abstract

We report stable (δ¹³C_(shell), δ¹⁸O_(shell)) and clumped isotope (Δ₄₇) compositions of modern and last glacial fossil snail shell carbonates from the Luochuan and Weinan sections on the central and southern Chinese Loess Plateau (CLP). Our study reveals that the average Δ₄₇ temperature (T₄₇) of modern snails is consistent with monitored temperatures during the snail growing season at the studied locations and is ~10 °C higher than that of fossil snails from glacial time. Moreover, the average δ¹³C_(shell) of modern snails is more depleted than that of fossils. We argue that the δ¹³C_(shell) cannot record changes in plant communities (i.e., the C3/C4 ratio) on the CLP and may mainly indicate arid conditions with depleted values reflecting reduced aridity. Additionally, the reconstructed snail body water δ¹⁸O (δ¹⁸O_(water)) of modern snails is more enriched than δ¹⁸O in modern growing season precipitation and δ¹⁸O_(water) of fossils. This contrast may be related to the high degree of evaporative enrichment of environmental water ¹⁸O in the body/ingested by modern snails under warm conditions. Therefore, we suggest that using δ¹⁸O_(shell) to directly reconstruct the oxygen isotopes of precipitation is difficult and that higher δ¹⁸O_(shell) and δ¹⁸O_(water) values probably indicate higher environmental temperature/stronger evaporative enrichment on glacial-interglacial timescales on the CLP.

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