TECTONIC PERIODICITY DURING THE MESOZOIC/CENOZOIC

From the Permo-Trias to today, the Earth has undergone spectacular changes in tectonic style, climate and sea-level. With the exception of bolide impact, solar radiation, and Earth orbit generated change, global tectonics, stratigraphy, climate and biological evolution are driven by plate tectonics and the assembly and disruption of Pangeas. Long wavelength first-order sea level change of several hundred metres generates high-stand carbonate platforms, climate ameliorataion and both oceanic and shelf euxinites. Low stands produce widespread continental red bed sequences and climatic variation. Glaciations generate very short wavelenght but large sea level changes.

The assembly of a Pangea involves collisional mountain building, intra plate compression, basin inversion, continental area shrinkage and sea level drop. Peripheral subduction generates extensional arcs and leads to continental extension aided by orogenic collapse. This leads to continental fragmentation with source rocks in marginal rifts. As continents disperse, ridge-push forces increase and marginal arcs become compressive. During dispersed-continent periods of rapid sea floor spreading and subduction, supra-subduction zone arc/ophiolite complexes are rapidly generated to collide with nearby rifted margins with sub-ophiolite blueschists. In this way, intra oceanic arc/ophiolites are added, by subduction polarity flip, to continental margins. These tectonic principles will be illustrated by the fragmentation and dispersal of Pangea during the Mesozoic and Cenozoic.