High-resolution elemental compositions of fluvial deposits in the Eastern Henan Basin and its implications for climatic variability over the last 3.5 Ma

Plio-Pleistocene climate variability in East Asia has been studied intensively using Chinese loess deposits and marine records from the South China Sea. However, long-term climate trends since the late Pliocene remain controversial due to the different sensitivity of proxy indicators to temperature and precipitation changes. Here, we present high-resolution elemental compositions of two high-quality fluvial sequences in the Eastern Henan Basin that reflect significant hydroclimate fluctuations over the last ∼3.5 Ma. Multivariate statistical analysis of ten elements (Si, K, Ca, Ti, Mn, Fe, Rb, Sr, Zr, and Ba) showed that the first principal component (PC1) includes detrital elements of Si, K, Ti, Mn, Fe, and Rb demonstrating significant fluctuations similar to the Ti/K ratio. The second principal component (PC2) includes Ca, Sr, and Ba, whose fluctuations match well with the Ca/K ratio. Combining the sedimentary facies and grain size analysis, we concluded that PC1 mainly reflects the hydrodynamics related to the summer monsoon while PC2 is associated with the dry-wet alternation induced by temperature and precipitation. Variations of PC1, PC2, and climate-sensitive elemental ratios demonstrated a multi-stage climatic evolutionary pattern, shifting from relatively humid climate conditions during the late Pliocene (3.5–2.8 Ma) to relatively dry conditions during the early Pleistocene (2.8–0.9 Ma), followed by the latest humid climate after 0.9 Ma. Our elemental results suggested that the hydroclimate changes of the Eastern Henan basin are mainly affected by the stepwise evolution of the East Asian summer monsoon.