The Role of Orogenic Collapse on Tectonic Inheritance of Passive Continental Margins

Abstract The break‐up and drift of continents is governed by the reactivation of structures in the lithosphere that occur in preference to formation of new structures during rifting. Numerical analyses indicate that mantle heterogeneities should be a first‐order control on tectonic inheritance; however, the importance of mantle relative to crustal structures has not been tested by observation in the geological record. Seismic anisotropy analysis using shear wave splitting of seismic waves are a useful tool to constrain past episodes of lithospheric deformation in the upper mantle. Analysis of published SKS directions colinear to orogenic trends, geometry of intracratonic faults and rift basins, and prolongation of basement structures into oceanic lithosphere all suggest a role of the mantle in controlling tectonic inheritance and crustal orogenesis. The geometry of the continental margin and temporal constraints point to a process involving lithosphere‐scale structures mimicked in the oceanic lithosphere due to orogenic collapse. The occurrence of fracture zones of the Labrador Sea that correspond with major structures in the Grenville, Appalachian, and older orogens suggest that deformation of the lithosphere and propagation of oceanic transforms are influenced by rheology in the upper mantle that formed during previous episodes of continental collision. If inheritance occurs at a lithospheric scale and is rooted in the mantle, it implies that orogenic collapse is an important mechanism for ocean opening along rifted continental margins. The geometry and morphology of the modern Atlantic Ocean may have been predetermined by Archean plate tectonic processes.