The forearc ophiolites of California formed during trench-parallel spreading: Kinematic reconstruction of the western USA Cordillera since the Jurassic

Ophiolites, fragments of oceanic lithosphere exposed on land, are typically found as isolated klippen in intensely deformed fold-thrust belts spanning hundreds to thousands kilometers along-strike. Ophiolites whose geochemistry indicates that they formed above subduction zones, may have been relics larger, once-coherent, tracts the leading edge an upper plate below which occurred; such were subsequently dismembered by deformation and erosion during orogenesis uplift. However, what extent first-order original coherence is maintained between ophiolitic difficult assess. Here, we aim evaluate whether Jurassic forearc ophiolites overlying complex rocks California, now scattered over 1000 km wider San Andreas Fault Zone, still maintain their lithospheric coherence. To this end (i) compile available crustal ages from all ophiolite belt western United States; (ii) review kinematically reconstruct post-middle occurred modern coast stable North American craton restore positions relative each other America, (iii) perform a paleomagnetic analysis sheeted dyke sections Mt. Diablo Josephine estimate orientation spreading axis at Californian formed. The latter reveals ridge likely trended ∼080–260°, near-perpendicular trench along margin belt. We show with these constraints, straightforward ridge-transform system can explain age distributions rates 6–7 cm/a. Our shows California be considered single sheet accreted supra-subduction zone ridge. In addition, kinematic provide novel constraints evolution accretionary orogens plates lost subduction.