Collisional intraplate deformation

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Intraplate compressional structures, such as inverted extensional basins, upthrusted basement blocks and whole lithospheric folds, play an important role in the tectonic framework of many cratons. Although compressional intraplate structures can occur in a number of dynamic settings, stresses related to collisional plate coupling appear to be responsible for the most important compressional intraplate deformations. Such structures can occur at distances of up to 1600 km from a collision front, both in back-arc (hinterland) and fore-arc (foreland) positions with respect to the subduction system controlling the respective orogen. The stratigraphic record of collision-related intraplate compressional deformation can contribute to the dating of orogenic activity affecting the respective plate margin. Four collision-related scenarios are envisaged for the build-up of intraplate compressional stresses: (1) during the initiation of subduction zones along passive margins or within oceanic basins, (2) during impedance of subduction processes caused by the arrival of an oceanic plateau, transform ridge or microcontinent at a subduction zone, (3) during the initial collision of an orogenic wedge with a passive margin, depending on the lithospheric and crustal configuration of the latter, the presence or absence of a thick passive margin sedimentary prism and convergence rates and direction, (4) during post-collisional over-thickening of an orogenic wedge. Crustal-scale foreland deformation reflects mechanical coupling between the orogenic wedge and its foreland at crustal levels; build-up of high fluid pressures in subducted sediments may account for their decoupling. Lithosphere-scale foreland deformation reflects mechanical coupling between the orogenic wedge and its forelands at the level of the mantle-lithosphere, possibly related to collisional lithospheric over-thickening and the development of mantle back-stops. Processes governing mechanical coupling/decoupling of an orogen and its forelands are still poorly understood.