Fold (geology)

A fold is the bending or curvature of one or more geological boundaries such as the layering of sedimentary rocks or the contact surfaces of a magmatic Ganges to its host rock. Folding is the process of wrinkle formation, referred to in the regional and historical geology but also from each other identifiable orogenic events.

With a folding rock layers are usually deformed wavy by external pressure. After the mechanical behavior of the rock layers in the folding of a distinction:

  • Competent rocks; usually dickbankige, hard rock layers that oppose deformation massive resistance and therefore change their thickness even at high lateral pressure only minimally, such as limestone
  • Incompetent rocks; plastic, easily deformable clay, marl or salt layers

If a sedimentary rock with deformed alternately competent and incompetent layers so "flows" a part of the incompetent matrix into the fold hinges.

For relatively homogeneous substrates are bending wrinkles form, with widely varying in strength layers are formed Scherf elderly or small-scale motions in very mobile rock such as magma melts flow folds. The highest point of a fold is called a saddle or apex ( anti form), the lowest point as a trough or trough ( synform ), located between the fold limbs.

By its origin, chronology or form belong together folds of an area are called wrinkle system. The term wrinkle system is furthermore used as a synonym for fold mountains or fold belt.

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