TEMPORALLY OVERLAPPING INTRACONTINENTAL CONTRACTION AND TERRANE ACCRETION IN THE CENTRAL NORTH AMERICAN CORDILLERA

Between the Gulf of Alaska and Baja California, the Cordilleran orogen of western North America is >5000-km long, up to 1000-km wide, and incorporates the following elements [listed in order of decreasing age]:

1. Neoproterozoic to early Paleozoic miogeocline 
2. mid-Paleozoic and early Mesozoic oceanic allochthons
3. mid- to late Mesozoic accretion-related orogenic belts [hinterland region]
4. mid- to late Mesozoic intracontinental contractional belts [foreland region]
5. mid-Mesozoic to early Cenozoic continental magmatic arcs

Tectonic elements of the central North American Cordillera owe their existence to supercontinental break-up/rifting [Rodinia; passive margin miogeoclinal development], drifting [emplacement of Antler/Sonoma allochthons], and incremental growth of western Laurentia [subduction-related magmatism/accretionary orogenesis]. Mesozoic subduction of oceanic lithosphere under ancestral North America resulted in the

1. collision of arc terranes [e.g. Klamath, Blue Mountains] with the Laurentian margin
2. development of thrust belts [e.g. Central Nevada, Sevier] on the continental interior
3. construction of batholiths [e.g. Sierra Nevada, Idaho] along the continental margin.

In response to long-lived [>100 Myr] ocean-continent plate convergence, compressional deformation propagated ~1000-km eastward from the subduction zone boundary into the continental interior. Jura-Cretaceous terrane accretion [Blue Mountains province] in the Cordilleran hinterland preceded and was partly synchronous with intracontinental contraction in the foreland region. At the latitude of Riggins, Idaho [~45N], ca. 144–92 Ma contraction across the arc–continent boundary and accretion-related Salmon River suture [SRS] was concurrent with thrusting east of the Cretaceous to Eocene Idaho batholith [Sevier thrust belt: STB]. Across this segment of the Cordillera, >300-km of ~E-W shortening was accommodated by the SRS and STB. Given their temporally overlapping nature [SRS and STB], and earlier history recorded by the SRS, the author proposes that terrane accretion in the Cordilleran hinterland drove deformation into frontal portions of the Sevier belt. An alternative to 'non-collisional' orogenesis, this model offers a collision-related explanation for intracontinental tectonism.