The Al/Ti ratio of the bulk sediments in Lake Luyang of Weihe Basin and its climatic significance implications

The elemental geochemical signatures preserved in lacustrine sediments offer key insights into sediment source-to-sink dynamics and paleoenvironmental evolution. In this study, we examine the Al/Ti ratio from the upper 221 m (spanning ca. 977 ka) of the LYH1 sediment core (34°48'43.49″N, 109°31'53.59″E) recovered from Lake Luyang in the Weihe Basin, Central China. By integrating highresolution Xray fluorescence (XRF) corescanning data, grainsize distributions, carbonate content, and multivariate statistical analyses, we systematically assess the paleoclimatic significance of the Al/Ti ratio and its potential as a proxy for hydrological changes in a semiarid to semihumid transitional region. Our results indicate that variations in the Al/Ti ratio are mainly controlled by terrigenous detrital input, which reflects changes in precipitation and hydrodynamic conditions. During relatively humid phases, increased rainfall strengthened fluvial discharge, transporting greater amounts of coarse-grained, Ti-enriched heavy minerals into the lake and thus lowering the Al/Ti ratio. Conversely, under drier conditions, diminished runoff limited the delivery of coarse sediment, leading to higher Al/Ti ratios due to the relative enrichment of fine-grained, Al-bearing clay minerals. Notably, episodic flood events during otherwise arid intervals could also introduce coarse particles, temporarily reducing the Al/Ti ratio and underscoring the complexity of hydroclimatic signals in lacustrine archives. Statistical analyses, including correlation and factor analysis, confirm that Al and Ti are predominantly of terrigenous origin, with Al concentrated in the fine fraction and Ti in coarse detrital minerals. The Al/Ti ratio shows strong coherence with other hydrodynamic and climatic proxies from the same core, such as the >62.5 μm/ To evaluate the regional and global relevance of the Al/Ti record, we compared the LYH1 data with well-established paleoclimate sequences, including the Luochuan loess magnetic susceptibility and grainsize records from the Chinese Loess Plateau, as well as the global benthic δ18O stack (LR04). The Al/Ti minima align with interglacial intervals, soil-development phases in loess-paleosol profiles, and lighter δ18O values, indicating that Lake Luyang sediments sensitively record orbitalscale climatic oscillations linked to East Asian monsoon variability. However, certain discrepancies, particularly during glacial stages (e. g., MIS 20), suggest that localized extreme precipitation events or reduced chemical weathering under cold-dry conditions can modulate the geochemical response, highlighting the need for careful interpretation in complex lacustrine settings.