title: Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.
abstract: Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.
authors.affiliation: School of Geosciences, Monash University, Melbourne, Victoria 3800, Australia. wouter.schellart@monash.edu
authors.forename: W P
authors.initials: WP
authors.lastname: Schellart
authors.forename: D R
authors.initials: DR
authors.lastname: Stegman
authors.forename: R J
authors.initials: RJ
authors.lastname: Farrington
authors.forename: J
authors.initials: J
authors.lastname: Freeman
authors.forename: L
authors.initials: L
authors.lastname: Moresi