Paleoenvironment reconstruction of the eastern Tethys Sea during the Pre-Onset Excursion

The Paleocene Eocene Thermal Maximum (PETM) is an event characterized by its significant negative carbon isotope excursion and is relatively well documented globally. Less well studied is the rapid warming event prior to the PETM known as the Pre-Onset Excursion (POE) at sub-millennial timescales, despite its potential in triggering or enhancing the subsequent PETM warming. Shallow marine environments especially those in low latitudes remain poorly documented despite their significant contributions for heat and moisture transport. Here we report a robust, high precision record from a well-preserved shallow marine section in the Tarim basin of the eastern Tethys Sea. While the POE’s impact is often unacknowledged due its rapid recovery, this study shows a drastically warped environment in terms ocean redox and nutrient conditions. The environmental perturbations occurred during the POE does not recover as readily as the PETM. Stable isotopes, major/trace elemental compositions and magnetic susceptibility data from a well–preserved sedimentary archive have allowed for a detailed reconstruction of the environmental changes occurred rapidly that are analogous to those that will be faced in our future climate condition. These paleoenvironmental proxies (ocean redox conditions, nutrient conditions and continental weathering) reflect substantial perturbations to the hydrologic cycle, ocean redox, and productivity of the eastern Tethys region. These changes likely laid the groundwork for the anomalously impactful PETM.