Differential paleoelevation changes in North China during the late Mesozoic: Evidence from stable isotopes and clumped isotopes

Abstract

The modern elevation of China decreases from the Tibetan plateau in the west to near sea level in the east across several topographic steps. A pronounced topographic step occurs in North China (NC), separating the plateaus and high mountains (elevations generally >1000 m) that dominate western NC from the plains and low mountain landscapes (elevations generally <500 m) of eastern NC. The topographic step in NC shapes modern climate and vegetation gradients and may have affected paleoenvironments and ecosystems in deep time. However, few studies have been conducted to explore paleoenvironmental and paleoelevation changes in NC, and thus the timing of its establishment is unclear. In this study, we use δ18O, δ13C and clumped isotope values of Middle Jurassic and Early Cretaceous paleosol carbonates from representative basins in western and eastern NC to constrain paleoenvironmental and paleoelevation changes during the late Mesozoic. Our δ13C and clumped isotope results suggest that the Ordos Basin of western NC maintained high paleoelevation (>1.5 km) during the Middle Jurassic-late Early Cretaceous, while the Hefei Basin of eastern NC experienced significant elevation reduction by the Early Cretaceous. Combined with paleogeographic, geophysical, and paleoecological evidence, these findings suggest that the lowering of eastern NC may have formed a topographic step across NC by Aptian time. This topographic change may have affected paleoclimate patterns and caused a climatic transition from dry to humid in eastern NC during this period. Broader topographic and environmental change may have occurred in Eastern China during the Early Cretaceous.