Trends and rhythms in global seafloor generation rate

Abstract

The primary purpose of this paper is to investigate the spreading and production rates of oceanic ridges for the last 180 Myr, based on the detailed analysis of eight oceanic units (North, Central, and South Atlantic basins, Southwest, Central, and Southeast Indian Ridge systems, Somalia basin, and the Pacific plate) and using the most recent timescale for oceanic isochrons. The global study of oceanic ridges presented here shows that (1) the average rate of spreading, which we computed by weighting the rates obtained at each basin by the relevant ridge lengths, is constant since ∼125 Ma at 53.4 ± 5.9 mm yr−1 (full rate), (2) the average surface production rate is 2.7 ± 0.2 km2 yr−1, and (3) the minimum oceanic crust production in volume, or flux, is 18.7 ± 2.9 km3 yr−1. These estimations are in close agreement (within ±10%) with other studies. However, the new results emerging from this analysis are the following: (1) The Cretaceous flux rates (in volume) might be only 10% higher than today over a short period of time (125–100 Myr). (2) The “pulse” of ocean crustal production (120–80 Ma) in the world total is predominantly the result of contributions from mantle temperature and oceanic plateaus but is not linked to the global spreading rate of oceanic ridges, as generally accepted. (3) The rates presented here differ from previously published models for the Cenozoic and show a general increasing trend in the last 50 Myr. (4) We finally suggest a possible ∼25 Myr pseudo‐periodicity of the oceanic production rate (in surface and in volume) at least during the last 75–80 Myr. These data could have a profound impact on a vast number of models including sea‐level changes and more generally on the chemical mass balance between ocean and continent, which is known to be a key parameter in the history of the Earth's climate and ocean chemistry.