Continental Growth in East Asia and North America: A Comparison

Although the growth of the North American and East Asian continents from Precambrian cores via accretion took place many 100's of millions of years apart in the Proterozoic and Phanerozoic respectively, the processes involved were actually very similar. Both landmasses were born in stages during the formation of the supercontinents of their times. During the supercontinent formation, older independent lithospheric blocks were sutured together, becoming a single unified craton. The newer, larger cratons would remain together, even after the supercontinents they cored began rifting apart. After the cratons formed, the geologic history of both southern Laurentia and the greater China region involved a long period of accretion in which volcanic arcs and continental terranes were welded to the cratons along collisional plate boundaries. While the growth of North America has largely ended, East Asia is still undergoing this accretion process as most obviously evidenced by the collision with the Indian sub-continent. Locally, the structures formed during the growth of these continents have controlled the development of younger structures. However in North America, younger rift features (e.g., Mid-continent, Southern Oklahoma aulacogen, Reelfoot, Rio Grande) regionally cut across the grain of Proterozoic accretionary trends. This is probably due to the fact that the old sutures have “healed” on a lithospheric scale. Except in North China, the reformed lithosphere of East Asia is generally too young to have healed. On both continents, there are good examples of the lithosphere being decratonized (e.g., Eastern North China and the eastern Basin and Range.