From buckling to asymmetric folding of the continental lithosphere: numerical modelling and application to the Himalayan syntaxes

Abstract

AbstractThe eastern and western Himalayan syntaxes are large-scale, coeval antiforms developed late in the history of India-Asia collision. We use two-dimensional finite element models of lithospheric folding to develop a mechanically plausible structural interpretation. The models mimic the coeval development of adjacent synformal basins, analogous to the Peshawar and Kashmir basins on either side of and adjacent to the western syntaxis. Pure-shear thickening and symmetric buckling accommodate shortening until, at a certain strain, an asymmetric thrust-like flow pattern occurs on a crustal to lithospheric scale. Similarities between geological data and calculated models suggest that lithospheric buckling is a basic response to large-scale continental shortening. To generalize these results, we suggest that a typical shortening history would include: (1) locking of an early thrust system in hinterland regions, followed by (2) pure shear shortening and symmetric buckling of the shortened lithosphere, and (3) loss of symmetry leading to the formation of an asymmetric fold in which a new thrust system will nucleate.