Synthesis of Phanerozoic Plate Tectonic Evolution of North America

Blakey, Ronald C.¹ (1) Northern Arizona University, Flagstaff, AZ

During the Phanerozoic, the North American (NAM) continent expanded on all four margins through a series of accretionary orogenic events. Most accretions involved microcontinents and arcs; only Baltica- Greenland and SE NAM- Africa involved direct continent-continent collision. By applying geodynamic principles proposed for southern Europe and NE NAM to overall North America, the tectonic history of the continent can be greatly simplified, especially with regard to the number of separate accretion events. Over 100 detailed time slices of Phanerozoic paleogeography and paleotectonics were prepared to build the following synthesis; orogenic terms generally in use are in parentheses: 1) the eastern and southern (all directions based on present coordinates) collisional events of NAM can be grouped into a) accretion of Taconia arc-microcontinent complex (Ordovician-Silurian Taconic orogeny); b) accretion of Avalonia and coeval collision of Baltica (Silurian-Early Devonian early phase of Acadian orogeny); c) accretion of Hun superterrane (from NE to SW Late Devonian-Pennsylvanian late phase of Acadian orogeny, Ouachita-Marathon orogeny); and d) collision of Africa (Penn-Perm Alleghenian orogeny). 2) Orogenic events in the Arctic region include a) accretion of Pearya (Silurian Taconic orogeny); b) accretion of Arctica and related terranes (Devonian-Mississippian Franklin orogeny); c) opening of Arctic Ocean and rotation of North Slope into Cordilleran terranes (Cretaceous Brooks Range orogeny); d) rotation of Greenland into Arctic (Cenozoic Eurekan orogeny). 3) Orogenic events in western NAM can be grouped into a) accretion of Antler terrane (Devonian-Mississippian Antler orogeny); b) collapse of Antler and other accreted terranes against NAM (Permian-Triassic Sonoman orogeny); c) initial accretion of Wrangellia to western NAM (Jurassic Nevadan orogeny); d) subsequent rotation, collapse, and transform migration of Wrangellia along western NAM (Cretaceous Sevier orogeny, Cenozoic Alaskan orogenies); e) aseismic ridge subduction and ensuing shallow subduction of Farallon Plate (early Cenozoic Laramide orogeny).