Eustatic change across the Paleocene-Eocene Thermal Maximum in the epicontinental Tarim seaway

The Paleocene-Eocene Thermal Maximum (PETM) offers an excellent opportunity to study the ecological and environmental responses to global warming. Discussing the so far poorly constrained amplitude and mechanisms of sea-level changes during the PETM is the principal goal of the present study from the epicontinental Tarim seaway. A negative carbon isotope excursion precisely constrains the stratigraphic position of the PETM event within the Qimugen Formation. Microfacies data show that tidal and lagoonal carbonates or sandstone characterizing the Tarim seaway in the pre-PETM stage were gradually replaced by open-marine to middle-ramp marlstones at PETM onset, by outer-ramp mudrocks in the syn-PETM stage, and eventually by middle-ramp carbonates in the post-PETM stage. A deepening paleo-water depth trend documents a transgressive sequence leading to maximum flooding during PETM peak. The content of planktonic foraminifera in Qimugen Formation sediments deposited below storm wave base indicates a minimum paleo-water depth of 20–50 m. Regional and global comparisons of sea-level curves suggest that this sea level rise documented in the Tarim epicontinental seaway during the PETM is a largely eustatic consequence of global warming, inducing extensive melting of high-mountain glaciers and thermal expansion of sea water.