Astronomically forced climate variability across the Eocene−Oligocene transition from a low latitude terrestrial record (Lühe Basin, South China)

Across the late Eocene to early Oligocene, Earth’s climate underwent a dramatic shift from Greenhouse to Icehouse, known as the Eocene−Oligocene transition (EOT). This globally synchronous climatic event is well-documented in marine records. However, there is a relative paucity of terrestrial records, particularly at low latitudes. In this study, we present a continuous and high-resolution terrestrial record across the EOT from the low-latitude Lühe Basin, Yunnan Province, South China. Combined with published magnetostratigraphy and 40Ar/39Ar dating of volcanic ashes in the Lühe Basin, we have constrained this record with a robust astronomical timescale. Our results, combined with previously published data from the region, reveal that the Lühe Basin experienced significant environmental and climate changes, from humid/warm to semi-humid/cool conditions, across the EOT. Cyclostratigraphic analysis of high-resolution elemental data reveal a significant switch in orbital forcing, from dominant eccentricity before ca. 34 Ma to combined eccentricity-obliquity-precession cycles after ca. 34 Ma. Atmospheric CO2 decline and subsequent Antarctic glaciation may have been a contributing factor in driving this orbital transition.