Nature Geoscience:Periodic changes in the Cretaceous ocean and climate caused by marine redox see-saw

发布时间:2019-08-25 放大 缩小


Periodic changes in sediment composition are usually ascribed to insolation forcing controlled by Earth’s orbital parameters. During the Cretaceous Thermal Maximum at 97–91?Myr ago (Ma), a 37–50-kyr-long cycle that is generally believed to reflect obliquity forcing dominates the sediment record. Here, we use a numerical ocean model to show that a cycle of this length can be generated by marine biogeochemical processes without applying orbital forcing. According to our model, the restricted proto-North Atlantic and Tethys basins were poorly ventilated and oscillated between iron-rich and sulfidic (euxinic) states. The Panthalassa Basin was fertilized by dissolved iron originating from the proto-North Atlantic. Hence, it was less oxygenated while the proto-North Atlantic was in an iron-rich state and better oxygenated during euxinic periods in the proto-North Atlantic. This redox see-saw was strong enough to create significant changes in atmospheric \(p_{\mathrm {CO}_2}\). We conclude that most of the variability in the mid-Cretaceous ocean–atmosphere system can be ascribed to the internal redox see-saw and its response to external orbital forcing.