Rifting, drifting, magmatic activity, and basin inversion on the passive margin of eastern North America
Abstract-The tectonic development of the passive margin of eastern North America between the Carolina trough and Scotian basin was considerably more complex than the classical two-stage, rift-drift model. Firstly, the transition from rifting to drifting was diachronous. In the southeastern United States, the rift-drift transition occurred after Late Triassic synrift deposition and before CAMP (Central Atlantic Magmatic Province) magmatism in earliest Jurassic time (~200 Ma). In maritime Canada, the rift-drift transition occurred after CAMP magmatism and synrift deposition in Early Jurassic time and before postrift deposition in early Middle Jurassic time (~185 Ma). Secondly, on both the southern and northern segments of the margin, the deformational regime changed substantially after rifting. Generally, NW-SE postrift shortening replaced NW-SE synrift extension. NE-striking reverse faults formed, and many of the rift-basin boundary faults had reverse displacements (inversion). In the southeastern United States, the change in the deformational regime occurred in Late Triassic/Early Jurassic time during the rift-drift transition. Simultaneously, diabase sills and dikes, many striking perpendicular to the trend of the rift basins, intruded the attenuated continental crust, and a massive wedge of presumed volcanic or volcaniclastic rocks developed near the continent-ocean boundary. In maritime Canada, the change in the deformational regime occurred during or after Early Jurassic time and before or during Early Cretaceous time (i.e., during the rift-drift transition and/or early stages of seafloor spreading).