SELF-SUBDUCTION OF A GLOBAL PLATE – THE BEGINNING OF PANGEA'S END?

The supercontinent cycles of continental lithosphere amalgamation followed by supercontinent demise and dispersal is one of the most fundamental topics in Earth history. Particularly abundant are the studies regarding Pangea, the most recent supercontinent, which progressively amalgamated over a period of time ranging from Carboniferous (ca. 320) to Upper Triassic (ca. 200 Ma). Although much is known of the different processes that took place during the accretion and dispersal of Pangea a number of key issues regarding the cause or causes for the initiation of its dispersal that are not fully understood. In particular, the causes of the initial stages of Pangea dispersal, prior to the onset of continental drifting in the early Jurassic, have been widely debated and are grouped into two main issues: post “Variscan-Alleghenian” orogenic collapse and the broad effects of a mantle superplume. However, both arguments fail to fully explain three of the main features that characterize the initiation of the Pangea breakup and dispersal: 1) the cause of the huge thermal event that affected most of the core of Pangea, accompanied by the genesis of radial rift basins; 2) the cause of the opening of the Neotethys ocean and the coeval genesis of the Cimmerian ribbon continent; and 3) the genesis of a key lithosphere-scale orocline, the Cantabrian or Iberian-Armorican Arc, located in the center of the supercontinent. Using a simple plate tectonic model that accounts for the geodynamic linkages between the features we propose a kinematic evolution to explain the origin of Pangean dispersal. We show that, under appropriate conditions, the oceanic part of a global plate (Paleotethys ocean as part of the Pangean global plate) can subduct under the same global plate, leading to a rapid change in its stress-strain configuration on a continental lithospheric scale. This scenario led to a radically different stress-strain configuration during the Upper Pennsylvanian-Early Permian that initiated processes that ultimately led to the breakup of Pangea. The process thus initiated was arrested when the Pangean global plate broke into two plates during the opening of the Neotethys ocean.