Tectonic inheritance at a continental margin

Abstract

GSA Today: v. 16, no. 2, doi: 10.1130/1052-5173(2006)016 2.0.CO;2 INTRODUCTION Forty years ago, the eastern margin of North America inspired Tuzo Wilson (1966) to ask, “Did the Atlantic close and then re-open?” The Wilson cycle of closing and opening of ocean basins incorporates the cyclic assembly and breakup of supercontinents. Alternate processes of extension and compression of continental margins suggest an important potential for tectonic inheritance and overprinting. Now, we recognize a succession of two complete Wilson cycles in eastern North America: closing of an ocean and assembly of the Rodinia supercontinent, breakup of Rodinia and opening of the Iapetus Ocean, closing of Iapetus and assembly of the Pangaea supercontinent, and breakup of Pangaea and opening of the Atlantic Ocean (Fig. 1). Precambrian rocks of cratonic North America indicate less well-defined, earlier cycles. Tectonic inheritance at a range of scales has been recognized in the successive continental margins preserved within the crust of present eastern North America, posing several fundamental questions. Does each episode of supercontinent assembly and breakup adapt to the tectonic framework of a preexisting continental margin and, in turn, leave a mold for the next episode? Is tectonic inheritance through successive Wilson cycles a first-order constraint on the processes through which continental crust is accumulated and continental fabrics evolve? Does tectonic inheritance in the shallow crustal structures reflect a pervasive fabric of the deeper lithosphere?