Global Phanerozoic sea levels from paleogeographic flooding maps

The validity of sea level estimates based on stratigraphic correlations has been debated since the 1990 s as relative sea level curves differ between sites due to local tectonics, different deposition rates and changes in dynamic topography. Here, we offer a new eustatic (global) sea level curve for the past 520 million years (Myrs) based on observations of global flooding. We use paleogeographic reconstructions to measure the area of today's exposed land that was flooded in the past (modern-land flooding). We then apply the modern global hypsometric slope to reconstruct the sea level history. We find minimum sea levels (comparable to today's level) towards the end of Pangea (210 Ma) and peak levels (-280 m higher than today) at 80 Ma when Pangea was widely dispersed. A first-order supercontinent cycle of 250 mil-lion years (Myrs) is recognized but we also document a second-order cycle of 37 Myrs that was previ-ously thought to be undetectable using the hypsometric method. The hypsometric slope is critical for reconstructing past sea levels, and steepening the hypsometric slope during Pangea assembly implies dramatically larger sea level fluctuations. Our new sea level curve shares strong similarities with strati -graphic constraints and correlates with seafloor production proxies throughout the Phanerozoic. Measurements of global flooding represent averages across great continental extents, making them less sensitive than stratigraphic analyses to regional-scale vertical land motion, such as from dynamic topog-raphy and hence more reliable for estimating eustatic sea level. This method can also help to identify local deviations caused by regional uplift or subsidence and serves to constrain geodynamic mechanisms for sea level change. Our new sea level reconstruction usefully tracks global variations in Phanerozoic eustatic sea level, but also opens opportunities to estimate such variations in deeper time.(c) 2022 The Author(s). Published by Elsevier B.V. on behalf of International Association for Gondwana Research. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/ 4.0/).

Automated summary

This study provides a new global sea level curve for the past 520 million years based on global flooding observations and paleogeographic reconstructions. The results show minimum sea levels at the end of Pangea and peak levels when Pangea was widely dispersed. The study also reveals a first-order supercontinent cycle and a previously undetectable second-order cycle, emphasizing the critical role of hypsometric slope in reconstructing past sea levels.