CRETACEOUS EVOLUTION OF CONTINENTAL MARGINS AS RELATED TO GLOBAL EVENTS

Abstract

The character and intensity of Cretaceous events in continental margins are genetically linked with the rate of oceanic crust accretion and intensity of endogenic (plume) activity of the Earth. This is most evidently proved by extraordinary events that occurred in continents in the 120-80 Ma interval as dependent on the accretion dynamics of the oceanic crust. The peak accretion was manifested in the Middle Cretaceous tectogenesis of unusual intensity, and a certain attenuation of this process caused more rapid subduction and higher volcanic activity in continental margins. The intense accretion of Cretaceous oceanic crust resulted in the growth of continental crust due to the increased area of continental margins and their greater thickness. The interval of 120-80 Ma is also a period of significant paleoclimatic and biological changes. The plate tectonic activity generally depends on the intensity of the lower mantle upwelling. Stages of intensive mantle plumes correlate with episodes of lithospheric plate reorganization and higher orogenic and magmatic activity, while their lower activity slows down the lithospheric processes. Against the background of continuous plume activity during the Phanerozoic, the interval of 120-80 Ma can be identified as a period of superplumes responsible for extraordinary consequences. Two Cretaceous superplumes, i.e., the Pacific and Atlantic-African, were of different intensity, dynamics, and duration, and this ultimately defined the difference between their boundaries with continental margins, convergent in the Pacific and passive in the Atlantic Ocean. The synchronous activity of plumes resulted in maximum intensity and a global character of events at the lithospheric level (120-80 Ma), whereas the discordant phases of superplumes were manifested by tectonic and magmatic processes of different types in the oceans and continental margins (80-50 Ma).