Global tectonics since the breakup of Pangea 180 million years ago: evolution maps and lithospheric budget

Pangea, the Earth's youngest single supercontinent, broke up 180 million years ago. Tectonic plates were subsequently formed by dispersal of the continental fragments and accretion of new oceanic lithosphere. The configurations of all the major lithospheric plates at 0, 20, 65, 95, 140, 180 Ma BP are reconstructed on six globes of the Earth, each with a radius of 10 cm. It appears that plate boundaries maintain a remarkably close fit on model globes of constant radii if the reconstructions include the recovery of subducted spreading patterns. This is illustrated with maps in equatorial orthographic, oblique orthographic and transverse Hammer-Aitoff projections. The snug fit of the tectonic plates at every tested time since the breakup of Pangea 180 Ma BP is consistent with the theory of plate tectonics on a non-expanding Earth and contradicts rapidly expanding Earth models. The areas of oceanic lithosphere produced and consumed during the past 180 Ma BP are estimated from surface measurements of the globes reconstructed on the basis of particular assumptions. These measurements suggest a consistent increase in the production rate of oceanic lithosphere during the past 140 Ma. It was decided to revise the assumptions and see if alternative reconstructions of the ancient spreading patterns on the floors of the Tethys and Eo-Pacific oceans could avoid implying an increase of lithospheric production rates with time. This appeared to be possible. The revised maps suggest that ophiolites older than 180 Ma BP may have been obducted in Cenozoic collision zones of the Himalayas, Andes, Rockies, and the western part of the Banda Arc (Timor, New Guinea). Estimates of the ocean floor production and consumption budget appear to be quite similar for both map series, and only the possible ranges are summarized here, time averaged for the past 180 Ma. World-wide production and consumption of oceanic lithosphere appears to have varied between 2.6 and 3.5 km² a^-1 at most. The mean of world-wide spreading velocities ranges between 2.4 and 3.5 cm a^-1 and world-wide means of subduction velocities lie between 4.2 and 6.3 cm a^-1. More accurate estimates are possible on the basis of particular assumptions and have been specified for the various time intervals distinguished: i.e., the Neogene (0-20 Ma BP), Palaeogene (20-65 Ma BP). Upper Cretaceous (65-95 Ma BP), Lower Cretaceous (95-140 Ma BP), and Middle and Upper Jurassic (140-180 Ma BP).