Sea level, biotic and carbon-isotope response to the Paleocene-Eocene thermal maximum in Tibetan Himalayan platform carbonates

During the Paleocene-Eocene Thermal Maximum (PETM, similar to 56 Ma), a large, negative carbon-isotope excursion (CIE) testifies to a massive perturbation of the global carbon cycle. Shallow-marine settings are crucial to understand the environmental and ecological changes associated with the PETM and the connection between continental and open-marine environments. Detailed sedimentological, paleontological, and geochemical analysis of a quasi-continuous succession of shallow-marine carbonates in the Tethys Himalaya of southern Tibet indicates that a relative rise in sea level coincided with PETM onset, continued through PETM core, and terminated with a regression at PETM recovery. At PETM onset, corresponding to the SBZ4/SBZ5 boundary, no obvious impact on biota and specifically on larger benthic foraminifera (LBF) is observed. The major biotic change occurs later on at PETM recovery, corresponding to the SBZ5/SBZ6 boundary. Our data suggest that relative sea level, rather than temperature, exerted the main control on benthic biota during the PETM. Although the delta C-13(org) values of organic matter are similar in the deep sea and shallow-marine continental margins, the delta C-13(carb) value of bulk carbonates are significantly C-13-depleted, which we attribute to environmental change driven by relative sea-level fluctuations.