Carbon cycle Cenozoic oceans

Authigenic Deposits. Carbon Cycle. Cenozoic Climate - Oxygen Isotope Evidence. Cenozoic Oceans - Carbon Cycle Models. Cosmogenic Isotopes. Mid-Ocean Ridge Geochemistry and Petrology. Rare Earth Elements and their Isotopes in the Ocean. River Inputs. Stable Carbon Isotope Variations in the Ocean. Uranium-Thorium Series Isotopes in Ocean Profiles. 

Carbon Dioxide (CO2) Cycle. Cenozoic Climate -Oxygen Isotope Evidence. Cenozoic Oceans -Carbon Cycle Models. Ocean Carbon System, Modeling of. Pore Water Chemistry. 

Shackleton N.J. (1985) Oceanic carbon isotope constraints on oxygen and carbon dioxide in the Cenozoic atmosphere. In The Carbon Cycle and Atmospheric CO2 Natural Variation Archean to Present (eds. E.T. Sundquist and W.S. Broecker), pp. 412-417. AGU Geophys. Monograph 32, Washington, D.C. 

The rate of CO2 release by volcanic and metamorphic processes is more directly tied to long-term tectonic processes than any other flux within the global carbon cycle, and has been approximated by rates of seafloor spreading and subduction. Estimates of global ocean crustal production for the Cenozoic imply a roughly 30% decrease in the volcanic... 

In an attempt to reconcile the two approaches, Frangois and Walker proposed in 1992 the addition of a new CO2 consumption flux to the carbon cycle, identified as the precipitation of abiotic carbonates within the oceanic crust, subsequent to its alteration at low temperature. This flux is directly dependent on deep water temperature, which has decreased by 8°C over the Cenozoic. An increase in the continental weathering rate might be compatible with a constant degassing rate, since the sink of carbon through low-temperature alteration of the oceanic crust is decreasing. The balance between input and output is thus still in place. However, this additional sink of carbon is poorly constrained. The present-day consumption of carbon is estimated to be about 1.4 X 10 mol y, but the kinetics of the process is essentially unknown. This attractive hypothesis still needs experimental verification. 

Figure 16. (a) Ca isotope record from marine carbonates (De La Rocha and DePaolo 2000). The variations are inferred to reflect variations in the isotopic composition of seawater (which is heavier by about 1,4%o). The small excursions of S Ca reflect changes in the global weathering cycle they are recast in (b) in terms of the ratio of the flux of calcium being delivered to the ocean by weathering (Fw) to the flux of Ca being removed from the ocean by carbonate sedimentation (c) Smoothed record of benthic foraminiferal 5 0 for the Cenozoic time period from Zachos et al. (2001). 

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