Land snail shell morphology as a new Paleomonsoon proxy

Area of Science:

• Paleoclimatology
• Biogeology
• Quaternary Science

Background:

• Reconstructing Asian summer monsoon (ASM) variations is crucial for understanding climate dynamics.
• Existing proxies like loess and speleothems show conflicting periodicities, hindering understanding of ASM forcing mechanisms.
• Physicochemical proxies in loess are complex due to pedogenesis and sedimentation rates, necessitating new, sensitive climate indicators.

Purpose of the Study:

• To evaluate land snail shell morphology as a novel proxy for reconstructing monsoonal climate variability.
• To investigate the potential of fossil land snail shells (Cathaica orithyia) as a sensitive indicator of past humidity and aridity.
• To compare new shell morphology-based climate records with existing Asian summer monsoon records.

Main Methods:

• Analysis of fossil land snail shell morphology, specifically aperture variations.
• Stratigraphic investigation of Cathaica orithyia shells from the Chinese Loess Plateau over the past 470,000 years.
• Comparison of shell morphology data with established paleoclimate records (speleothem δ18O, loess proxies) to identify dominant periodicities.

Main Results:

• Land snail shell morphology exhibits distinct cyclicity, aligning with orbital forcing periods.
• The shell morphology record shows precessional (23 kyr), obliquity (41 kyr), and eccentricity (100 and 400 kyr) cycles.
• A strong precessional signal in shell morphology suggests its dominance in driving ASM variations.

Conclusions:

• Land snail shell morphology is a reliable proxy for reconstructing past humidity and aridity, influenced by multiple climate factors.
• The Asian summer monsoon is likely forced by multiple orbital periodicities, with precession playing a predominant role.
• Biological proxies like snail shell morphology offer enhanced sensitivity and a more comprehensive response to climate change compared to traditional proxies.