Mechanical controls on collision-related compressional intraplate deformation

Intraplate compressional features, such as inverted extensional basins, upt hrust basement blocks and whole lithospheric folds, play an important role in the structural framework of many cratons. Although compressional intrapl ate deformation can occur in a number of dynamic settings, stresses related to collisional plate coupling appear to be responsible for the development of the most important compressional intraplate structures. These can occur at distances of up to +/-1600 km from a collision front, both in the fore- are (foreland) and back-are (hinterland) positions with respect to the subd uction system controlling the evolution of the corresponding orogen. Back-a re compression associated with island arcs and Andean-type orogens occurs d uring periods of increased convergence rates between the subducting and ove rriding plates. For the build-up of intraplate compressional stresses in fo re-are and foreland domains, four collision-related scenarios are envisaged : (1) during the initiation of a subduction zone along a passive margin or within an oceanic basin; (2) during subduction impediment caused by the arr ival of more buoyant crust, such as an oceanic plateau or a microcontinent at a subduction zone; (3) during the initial collision of an orogenic wedge with a passive margin, depending on the lithospheric and crustal configura tion of the latter, the presence or absence of a thick passive margin sedim entary prism, and convergence rates and directions; (4) during post-collisi onal over-thickening and uplift of an orogenic wedge. The build-up of colli sion-related compressional intraplate stresses is indicative for mechanical coupling between an orogenic wedge and its fore- and/or hinterland. Crusta l-scale intraplate deformation reflects mechanical coupling at crustal leve ls whereas lithosphere-scale deformation indicates mechanical coupling at t he level of the mantle-lithosphere, probably in response to collisional lit hospheric over-thickening of the orogen, slab detachment and the developmen t of a mantle back-stop. The intensity of collisional coupling between an o rogen and its fore- and hinterland is temporally and spatially variable. Th is can be a function of oblique collision. However, the build-up of high po re fluid pressures in subducted sediments may also account for mechanical d ecoupling of an orogen and its fore- and/or hinterland. Processes governing mechanical coupling/decoupling of orogens and fore- and hinterlands are st ill poorly understood and require further research. Localization of collisi on-related compressional intraplate deformations is controlled by spatial a nd temporal strength variations of the lithosphere in which the thermal reg ime, the crustal thickness, the pattern of pre-existing crustal and mantle discontinuities, as well as sedimentary loads and their thermal blanketing effect play an important role. The stratigraphic record of collision-relate d intraplate compressional deformation can contribute to dating of orogenic activity affecting the respective plate margin. (C) 1998 Elsevier Science B.V. All rights reserved.