Exploring the relationship between Late Miocene ocean carbon shift and productivity

The Late Miocene ocean carbon shift (LMOCS) is the most recent event characterized by synchronous decrease in both surface and deep water(δ¹³C) at a global scale, which is generally attributed to the biogenic pumping.When biogenic bloom event appears, the biogenic pump will start working to facilitate(δ¹³C) fractionation.As the results, benthic foraminiferal(δ¹³C) decreases.However, this inference is recently challenged by increasing facts and evidence.Generally, changes in paleo-productivity, biogenic bloom and the role and efficiency of biogenic pump can be reconstructed using paleontological and geochemical proxies.A compilation of these proxy records reveals the debates between the LMOCS and productivity.The onset and the cease of most biogenic bloom events led and lag the LMOCS, respectively.And the LMOCS is globally synchronous while the biogenic bloom event is not.Moreover, the synchronization of surface and deep water is also contrary to the principle of biologic pump.We thus propose that other reasons besides the changes in productivity should have accounted for the LMOCS.A further insight into the global hydrologic and carbon cycle, an improved reconstruction of atmospheric CO₂level, and computer climate simulation studies will together help to unveil the driving mechanisms for the LMOCS.