Fold-and-thrust belt

A region of shortened crust composed of linked folds and thrust faults, typically formed as rock layers are compressed and pushed over one another.

Thrust fault: A low-angle reverse fault along which older or deeper rocks move over younger or shallower rocks. These faults accommodate crustal shortening and commonly link the belt’s folds.
Crustal shortening: A reduction in the horizontal length of a section of Earth’s crust caused by deformation. The belt is a regional expression of shortening across a broad zone.
Balanced cross-section: A geological cross-section restored to show that its layers and lengths remain consistent with an undeformed state. Balancing tests whether a proposed arrangement of folds and thrusts is geometrically plausible.
Himalayan foothills: The southern mountain-front region of the Himalaya, where India underthrusts Eurasia beneath folded and faulted rocks. The Himalaya’s foreland-facing structures provide a major active example of a thrust belt.
Fault-bend fold: A fold formed as a rock layer moves over a bend in a thrust-fault surface. Changes in fault geometry bend the layers carried through the belt.
Folding: The bending of originally planar rock layers without breaking their continuity. Folds record compression alongside the belt’s fault displacements.
Seismic reflection: A geophysical method that images underground structures from reflected sound waves. Seismic profiles reveal buried thrust surfaces and folded strata beneath cover.
Canadian Rockies: A mountain range in western Canada whose eastern ranges include sedimentary rocks transported eastward on thrust faults. Their exposed thrust sheets illustrate large-scale shortening at a continental margin.
Fault-propagation fold: A fold that forms above the tip of a thrust fault as the fault propagates through rock. Folding can precede or accompany a thrust as its tip advances.
Reverse fault: A fault on which the hanging wall moves upward relative to the footwall under compression. Thrust faults are low-angle members of the reverse-fault family.

Linked from 11 pages