Scientists have managed, thanks to 3D modeling, to go back to the oldest geological times to trace the evolution of the oceans for about 540 million years.
It was at the beginning of this so-called Cambrian period that the first forms of complex life appeared – beyond simple single-celled organisms – such as trilobites, these marine arthropods that disappeared during one of the first mass extinctions.
millions of years”,”text”:”The great plans for the organization of living beings, namely life as we know it today, emerged 500millions of years ago”}}”>The great plans for the organization of life, namely life as we know it today, emerged 500 million years ago.details for theAFP paleoclimatologist Alexandre Pohl, CNRS researcher at the Biogeosciences laboratory in Dijon and main author of the study.
Then, during the Ordovician, 460 million years ago, biodiversity experienced a real explosion. Probably thanks to the oxygenation of the waters, where the levels of oxygen concentration made the places conducive to the development of fauna.
It is commonly accepted that this
marine oxygenation results from changes in oxygen in the atmosphere. But by refining several existing climate models, Alexandre Pohl and his team discovered that these evolutions were also largely dictated by plate tectonics, the movements of reorganization of the position of the continents.
They carried out numerical simulations of ocean currents, modified by plate tectonics, which show a
major decoupling between surface and deep ocean oxygenationexplains the researcher from the University of Bourgogne-Franche Comté.
Their model thus suggests that before the biodiversity explosion of the Ordovician, the deep ocean was poorly oxygenated even though the concentrations in the atmosphere were already relatively high. Sign that the oxygenation of deep waters then intervened by the geological movement of the plates, independently of what was happening in the air.
540 million years ago, the supercontinent that preceded Pangea, called Pannotia, began to break up. Over the course of the reconfigurations, which span millions of years, the levels of marine oxygen have varied, probably playing a key role in the evolution of species.