Intra-oceanic subduction shaped the assembly of Cordilleran North America

The western quarter of North America consists of accreted terranes—crustal blocks added over the past 200 million years—but the reason for this is unclear. The widely accepted explanation posits that the oceanic Farallon plate acted as a conveyor belt, sweeping terranes into the continental margin while subducting under it. Here we show that this hypothesis, which fails to explain many terrane complexities, is also inconsistent with new tomographic images of lower-mantle slabs, and with their locations relative to plate reconstructions. We offer a reinterpretation of North American palaeogeography and test it quantitatively: collision events are clearly recorded by slab geometry, and can be time calibrated and reconciled with plate reconstructions and surface geology. The seas west of Cretaceous North America must have resembled today’s western Pacific, strung with island arcs. All proto-Pacific plates initially subducted into almost stationary, intra-oceanic trenches, and accumulated below as massive vertical slab walls. Above the slabs, long-lived volcanic archipelagos and subduction complexes grew. Crustal accretion occurred when North America overrode the archipelagos, causing major episodes of Cordilleran mountain building.

[1]  G. Morra,et al.  Evidence of lower-mantle slab penetration phases in plate motions , 2008, Nature.

[2]  A. Şengör,et al.  Was the Laramide orogeny related to subduction of an oceanic plateau? , 1981, Nature.

[3]  R. Hilst,et al.  Buckling instabilities of subducted lithosphere beneath the transition zone , 2007 .

[4]  T. Lawton,et al.  Carboniferous to Cretaceous assembly and fragmentation of Mexico , 2001 .

[5]  W. G. Gilbert,et al.  Geology of southwestern Alaska , 1994 .

[6]  A. Leier,et al.  Continental-scale detrital zircon provenance signatures in Lower Cretaceous strata, western North America , 2011 .

[7]  T. Becker,et al.  Subduction to the lower mantle - a comparison between geodynamic and tomographic models , 2012 .

[8]  G. Masters,et al.  Global P and PP traveltime tomography: rays versus waves , 2004 .

[9]  R. Enkin,et al.  Deciphering shallow paleomagnetic inclinations: 2. Implications from Late Cretaceous strata overlapping the Insular/Intermontane Superterrane boundary in the southern Canadian Cordillera , 2003 .

[10]  Maisha Amaru,et al.  Towards absolute plate motions constrained by lower-mantle slab remnants , 2010 .

[11]  N. Massey Metchosin Igneous Complex, southern Vancouver Island: Ophiolite stratigraphy developed in an emergent island setting , 1986 .

[12]  Donald M. Hussong,et al.  The Eastern Pacific Ocean and Hawaii , 1989 .

[13]  E. Tric,et al.  Dependency of slab geometry on absolute velocities and conditions for cyclicity: insights from numerical modelling, , 2012 .

[14]  Hans-Peter Bunge,et al.  Mesozoic plate-motion history below the northeast Pacific Ocean from seismic images of the subducted Farallon slab , 2000, Nature.

[15]  Lijun Liu,et al.  Reconstructing Farallon Plate Subduction Beneath North America Back to the Late Cretaceous , 2008, Science.

[16]  R. A. Price,et al.  Tectonic accretion and the origin of the two major metamorphic and plutonic welts in the Canadian Cordillera , 1982 .

[17]  Margarita López Martínez,et al.  Stratigraphy, geochronology, and geochemistry of the Laramide magmatic arc in north-central Sonora, Mexico , 2011 .

[18]  J. Connelly,et al.  Duration of Late Cretaceous–early Tertiary magmatism in east-central Sonora, Mexico , 2001 .

[19]  S. Uyeda,et al.  Tectonic History of the Western Pacific , 2013 .

[20]  Gary L. Pavlis,et al.  Unraveling the geometry of the Farallon plate: Synthesis of three-dimensional imaging results from USArray , 2012 .

[21]  E. Moores Ophiolites, the Sierra Nevada, “Cordilleria,” and Orogeny along the Pacific and Caribbean Margins of North and South America , 1998 .

[22]  R. Müller,et al.  The role of oceanic plateau subduction in the Laramide orogeny , 2010 .

[23]  E. Humphreys,et al.  Seismically imaged relict slab from the 55 Ma Siletzia accretion to the northwest United States , 2011 .

[24]  W. J. Morgan,et al.  Convection Plumes in the Lower Mantle , 1971, Nature.

[25]  P. Steerenberg,et al.  Targeting pathophysiological rhythms: prednisone chronotherapy shows sustained efficacy in rheumatoid arthritis. , 2010, Annals of the rheumatic diseases.

[26]  S. Johnston The Great Alaskan Terrane Wreck: reconciliation of paleomagnetic and geological data in the northern Cordillera , 2001 .

[27]  Guust Nolet,et al.  Two-stage subduction history under North America inferred from multiple-frequency tomography , 2008 .

[28]  B. Steinberger,et al.  On the uncertainties in hot spot reconstructions and the significance of moving hot spot reference frames , 2005 .

[29]  T. Hilde,et al.  Tectonic evolution of the northern Pacific plate and Pacific-Farallon Izanagi triple junction in the Late Jurassic and Early Cretaceous (M21-M10) , 1988 .

[30]  Eleonore Stutzmann,et al.  Understanding seismic heterogeneities in the lower mantle beneath the Americas from seismic tomography and plate tectonic history , 2007 .

[31]  P. Coney,et al.  Cordilleran suspect terranes , 1980, Nature.

[32]  R. Müller,et al.  Controls on back‐arc basin formation , 2006 .

[33]  T. Atwater Plate tectonic history of the northeast Pacific and western North America , 1989 .

[34]  D. Giardini,et al.  Signatures of downgoing plate-buoyancy driven subduction in Cenozoic plate motions , 2011 .

[35]  M. Gurnis,et al.  Mantle Convection with Plates and Mobile, Faulted Plate Margins , 1995, Science.

[36]  W. Dickinson Accretionary Mesozoic–Cenozoic expansion of the Cordilleran continental margin in California and adjacent Oregon , 2008 .

[37]  W. Spakman,et al.  Intra-Panthalassa Ocean subduction zones revealed by fossil arcs and mantle structure , 2012 .

[38]  B. Steinberger,et al.  Absolute plate motions and true polar wander in the absence of hotspot tracks , 2008, Nature.

[39]  M. Mihalynuk,et al.  Cache Creek terrane entrapment: Oroclinal paradox within the Canadian Cordillera , 1994 .

[40]  C. Hart,et al.  Yellowstone in Yukon: The Late Cretaceous Carmacks Group , 1996 .

[41]  Mark Turner,et al.  Plate tectonic reconstructions with continuously closing plates , 2012, Comput. Geosci..

[42]  W. Ernst Accretion of the Franciscan Complex attending Jurassic–Cretaceous geotectonic development of northern and central California , 2011 .

[43]  M. Wortel,et al.  Shallow slab detachment as a transient source of heat at midlithospheric depths , 2001 .

[44]  J. Royer,et al.  Revised plate motions relative to the hotspots from combined Atlantic and Indian Ocean hotspot tracks , 1993 .

[45]  Karin Sigloch,et al.  Mantle provinces under North America from multifrequency P wave tomography , 2011 .

[46]  R. Müller,et al.  Testing absolute plate reference frames and the implications for the generation of geodynamic mantle heterogeneity structure , 2012 .

[47]  E. Engdahl,et al.  A new global model for P wave speed variations in Earth's mantle , 2008 .

[48]  Maria Seton,et al.  Global continental and ocean basin reconstructions since 200 Ma , 2012 .

[49]  McSween Hy,et al.  Evidence for Life in a Martian Meteorite , 1997 .

[50]  Allan Cox,et al.  Relative Motions Between Oceanic and Continental Plates in the Pacific Basin , 1986 .

[51]  Sri Widiyantoro,et al.  Global seismic tomography: A snapshot of convection in the Earth: GSA Today , 1997 .

[52]  A. Basu,et al.  Geochemical evidence for a subducted infant arc in Franciscan high-grade-metamorphic tectonic blocks , 2005 .

[53]  R. Müller,et al.  Global plate motion frames: Toward a unified model , 2008 .