Interactions between the Earth Sphere and its constraint on the progress of anoxic-oxic in the Cretaceous Ocean

The Cretaceous is an important period in which occurred many geological events, especially the OAEs (Oceanic Anoxic Events) characterized by black shales, and theoxic process characterized by CORBs (Cretaceous Oceanic Red Beds). This paper describes the causative mechanism which explains how the oceanic environment changed from anoxic to oxic in Cretaceous. Two typical events show different results that caused by interactionsoftheEarthSpheres. Here we propose that the rise of atmospheric CO₂ occurred because the enhanced submarine volcanism-was abruptly and permanently diminished during the Cretaceous. The Cretaceous large-scale submarine volcanism caused the concentration of CO₂. The releasing of the inner energy of the lithosphere and thedistribution oflandwhich caused the increasing of atmospheric temperature. This change presented the same trend as the oceanic water temperature, and caused the decreasing of O₂ concentration in the Cretaceous ocean, and then the OAEs occurred. The lithosphere produced volume of lava in the upper oceanic crustwhich contained Fe in the seafloor. When thehydrothermal fluids alteration of oceanic crust and the seawater/basalt interactions (including microbes alteration of submarine basaltic glass), the element Fe dissolved in seawater. Iron is a micronutrient essential for the synthesis of enzymes required for photosynthesis in oceanic environment, it could spur phytoplankton growth rapidly. The photosynthesis of phytoplankton which can consume carbon dioxide is in much of the world's oceans, wherever they are in atmosphere or in ocean. This process could produce equal oxygen. And then, the oxic environment characterized by red sediment which is rich in Fe³⁺ appeared. The data show rhythm of the anoxic and oxic from south Tibet and DSDP/ODP section, which the anoxic is often accompanied by the occurrence of oxygen rich environment.Undoubtedly, the anoxic andoxic in the Cretaceous Ocean were controlled by the mutually dependent processes of the Earth system which included lithosphere, hydrosphere, atmosphere and biosphere. An important conclusion of this study is that the black shalesand the oceanic red beds are caused by the same reason, but led different results. The anoxic and oxic in the Cretaceous ocean were caused by volcanic activities, but they were of different causative mechanisms. The former was based on physical and chemical process, while the latter involved more complicated bio-oceanic-geochemistry process.