Assessing the Reliability of Early Marine Cements in Recording Changes in Seawater Redox Conditions Across the Late-Devonian Mass Extinction

The Late-Devonian Mass Extinction (LDME) extinguished up to 40% of all marine species, with evidence suggesting marine anoxia was the primary cause. This study performs rare earth element analysis of early marine cements from reefal limestones from Australia and Scotland to show that these cements capture a marine anoxic signature across the LDME for the first time, directly implicating marine anoxia and by extension, the rise of land plants, as the cause of the LDME. This work also demonstrates that early marine cements serve as reliable proxies for recording changes in seawater redox conditions over whole-rock analysis.