Astronomical forcing of the hydrological cycle in the Weihe Basin (North China) during the middle to late Eocene

The middle to late Eocene marked a key transition from greenhouse to coolhouse. However, a lack of highresolution and temporally well-constrained continental records hinders our understanding of the driving mechanisms of climate change during this period. In this study, we combined magnetostratigraphy and cyclostratigraphy to establish a high-resolution astronomical time scale spanning the middle to late Eocene (-42.4 Ma to -35.3 Ma) through a 214-m succession of the continental Honghe Formation in the Weihe Basin, North China. Our results show that variability in the hydroclimate of the Weihe Basin at this time was dominated by eccentricity (-405 kyr and -100 kyr) and obliquity (-1.15 Myr and -173 kyr) forcing. Meridional insolation gradient variations controlled by obliquity, and low-latitude summer insolation via eccentricity modulation of precession jointly controlled paleolake evolution in the basin during the -42.4 Ma to -35.3 Ma interval, rather than being controlled by eccentricity or obliquity as previously inferred. Our study provides new insights into the driving mechanisms of orbital-scale hydroclimate evolution in continental lake basins during the ice-free middle to late Eocene.

Automated summary

In this study, a high-resolution astronomical time scale spanning the middle to late Eocene was established using magnetostratigraphy and cyclostratigraphy. The results showed that hydroclimate variability in the Weihe Basin during this period was mainly controlled by eccentricity and obliquity forcing. The findings provide new insights into the driving mechanisms of orbital-scale hydroclimate evolution during the ice-free middle to late Eocene in continental lake basins.