Karst environment evolution processes over the past 14 ka inferred from the geochemical composition of a 650‐cm peat record in southwestern China

Abstract

Reconstructing the hydroclimatic history of the karst region in southwestern China (SWC) since the last deglaciation is crucial for understanding the dynamics and evolution of the Asian monsoon and its influence on the chemical weathering of carbonate rocks. Numerous studies have reconstructed paleoenvironmental variability in this region using archives such as lacustrine sediments and stalagmites. However, studies utilizing peat archives that span this period remain limited, and the use of geochemical elements in such settings is underutilized. This study presents a comprehensive element dataset derived from non‐destructive X‐ray fluorescence core scanning of a 650‐cm‐long peat core collected from the southwestern Guizhou Plateau in SWC. Based on an age‐depth model established with 12 AMS 14 C dates, our findings indicate that geochemical proxies, including the Si/Ti, Ti/K, Zr/Rb, and Rb/Sr ratios, reflected in principal component 1 (PC1), primarily reflect exogenous elemental influx. Furthermore, arboreal pollen percentage correlates positively with PC1, suggesting that PC1 serves as a proxy for precipitation and associated catchment weathering processes. In contrast, the PC2 score covaries with yellowness (b*), tracking the growth and accumulation of peatland vegetation. These findings demonstrate the utility of elements and chroma from peat archives for interpreting environmental shifts in this karst region. The record reveals three distinct intervals since 14 000 cal. a BP: (i) from 14 000 to 4500 cal. a BP, generally humid punctuated by intermittent millennial‐scale dry events; (ii) from 4500 to 3600 cal. a BP, there was a shift in sedimentation patterns and a transition towards a drier climate marked by high instability; and (iii) from 3600 to 1400 cal. a BP, was a dry period characterized by minimal exogenous input but enhanced peatland vegetation biomass. Comparisons with regional and global records suggest that these hydroclimatic shifts in SWC were primarily modulated by Indian Summer Monsoon intensity, driven by the meridional migration of the Intertropical Convergence Zone (ITCZ) and El Niño–Southern Oscillation (ENSO) variability. This study provides valuable insights into the climatic and vegetation history of SWC, enhancing our understanding of the paleoenvironmental significance of elemental compositions in karst peat archives.

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