A period of biological upheaval in the oceans 116-114 million years ago was caused by a 2-million-year period of cooling, reports a paper published online this week in Nature Geoscience. The work suggests that this cooling was caused by the extensive burial of organic carbon, which reduced atmospheric carbon dioxide concentrations.
Thomas Wagner and colleagues analysed the chemical composition of marine sediments sampled from the North Atlantic Ocean to assess the timing and magnitude of a major cooling event in the surface ocean 116 to 114 million years ago. They showed that this period of cooling coincided with a reduction in the abundance of some groups of marine plankton and extinctions in certain groups of surface-dwelling microorganisms. Numerical simulations suggest the cooling was linked to the burial of over 800,000 gigatons of carbon during this time, primarily in the Atlantic, Southern and Tethys oceans.