Thrustfaulted

Thrustfaulted is an adjective used in geology to describe rocks or geological terranes that have undergone thrust faulting. Thrust faulting refers to deformation produced by thrust faults, which are low-angle reverse faults formed under compressional tectonics. In thrust faulting, slices of crust are displaced upward and sometimes over adjacent rocks, yielding imbricate stacks, discontinuous repetitions of stratigraphy, and allochthonous blocks.

The term is commonly applied to rocks that have been transported significant distances along fault planes during continental collision or subduction. Thrust faulting often occurs in mountain belts where crustal shortening is accommodated by the upward movement of large crustal slices. This process can create complex structural configurations such as duplex fault systems, multiple horse-shoe–shaped ramps, and nappe-like thrust sheets. The resulting tectonostratigraphic architecture may include overturned or repeated sequences, detached from their original stratigraphic positions.

Field and laboratory indicators of thrust faulting include the presence of low-angle fault surfaces, hanging-wall overprinting, drag and sheath folds, shear zones with mylonite development in deeper levels, and associated metamorphism reflecting burial and deformation histories. Thrust faulting can be accompanied by changes in rock type and metamorphic grade, depending on the depth and temperature of deformation.

Thrustfaulted rocks contrast with simple reverse faults by their characteristic low fault dips and large horizontal displacements. They may occur in thin-skinned tectonics, affecting only upper crustal units, or in thick-skinned tectonics, involving deeper basement rocks and multiple crustal levels.