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Thin-skinned deformation is a style of deformation in plate tectonics at a convergent boundary which occurs with shallow thrust faults that only involves cover rocks (typically sedimentary rocks), and not deeper basement rocks.
The thin-skinned style of deformation is typical of many fold and thrust belts developed in the foreland of a collisional zone or back arc of a continental volcanic arc. This is particularly the case where a good basal decollement exists, usually in a weaker layer like a shale, evaporite, or a zone of high pore fluid pressure. This was first described in Rocky Mountains of the United States, as part of the Sevier Orogeny.
In the rock record, this will increase the influence of more surficial rocks, which usually includes sedimentary rocks. Typically, you will see repeated sections of the same rock over and over as thrust faults, coming up from the decollement, stack the same layer on top of itself. The sediments that are created by this type of deformation are typically lithic sandstones.